View Full Version : Derbi Reactivation Project--The Return of the Wicked GPR

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09-22-2015, 03:44 AM
The photo hosting service PhotoBucket has gone psycho. I'm slowly repairing my threads. I'm starting with the most recent and working backwards. ¯\_(ツ)_/¯


My all time favorite bike is the 05 GPR that I sourced from Atlanta. A Saab buddy of mine picked it up, crated it, and delivered it to a dock where it was then trucked out to Oakland. I picked it up there with my Saab. The warehouse guys said "theres no way you are getting that in there." I just proceeded to prove him wrong. :P




I put a lot of effort into this bike. Engine, brakes, suspension, tires--the only thing I didn't really mess with was the looks, because I really love the styling of the 05 GPR.


Then almost exactly three years ago I was crashed on it by a young woman in a Honda Civic. This broke many of my bones, messed up my knee, and a bunch of rear teeth. Even three years later I'm nowhere close to the physical state before the crash. But I wasn't the only one hurt--my bike suffered greatly too. I tried a few things to get it running again, but it really needed some serious effort. So I pulled it apart, brought it into the kitchen, and set it to non-op. CA speak for I'm not paying any reg fees while I can't ride my bike.


I've slowly been gathering parts for it, and now I have enough to maybe get it running again. This will very much be a project where the bike comes together, and then I slowly rebuild it to where I want to take it. I was going to wait until I had all the bits, but I so miss this bike that I have to do something about it. That means a temporary engine, temporary plastics, and well a few of the things that I wanted to do. But being a long term project it's okay to do things in steps.


Some fun things I've already picked up for it

The Forks!
I was able to get the forks! Yeah that's all I'm going to say about them for now, but Scotty knows what I'm talking about (and if you want a set let me know. I'll help you get them too.).

Jolly Moto
I always wanted a Jolly Moto pipe for the GPR. I have one on the Monza, and it's so awesome. One popped up on eBay a while back, and no one went for it. It got relisted, and still--so I bought it. It's really not the right match for my engine, but well it's a Jolly Moto!

The previous build featured the 45mm stroked Airsal Xtreme kit. I still haven't figured out how to make that happy, so for this temporary engine build I'm going to go with tho 40mm stroked Xtreme kit, also with the Airsal crank.

I've been running the "MotoGP" tires on this bike. I had sourced a rear wheel from the 2T 125 because it's wider. But there were too many differences so I went back to the 50cc rear wheel. This meant that the tires didn't properly fit the wheels. Since then Sava has come out with the MC50 super soft. Oh yeah! Same compound that they use to make the track tires. They probably wont last all that long, but who the hell cares when you can ride street tires like that on a fifty! Benji only had the front in stock, so I'm going to have to wait for the rear.

I finally found a place that still makes the GPR50 fiberglass farings. It takes a while, and they are pricey. But I fully intend to go for it--eventually. For now though I have a set from an 02 GPR, and I'm going to try to make those work.


I've been running the 16x18 radial Brembo on the GPR, but it's time to upgrade (the 16x18 went to the Red bike, and is now on the Track Bike).

Okay that's a good opener. I'll probably be updating the OP from time to time.

09-22-2015, 03:57 AM
Last week I made an appointment to visit Treats. Need to get some parts, you know?


To get this bike back on the road meant building a temporary engine. My friend Jason put an EBE075 into his 2003 GPR, and gave me the left overs of his stock engine. It's missing a bunch of bits, including a crank, and all the clutch parts, but it's a great start. Tonight it was a good opportunity to split the cases, and find out what's inside.

I use to have a Puch clutch puller, but that got lent out to those whom will not be mentioned. So I needed a replacement. Now the Puch puller isn't really the right part for the job so you have to modify it. It's the closest thing that Treats sells for this application, and with a bit of cutting with the hacksaw you are in business. I didn't make great cuts. The bolts needed to split the cases are M6 (this might be off I'll check it and update). You can actually use the engine mounting bolts (you'll have to source a second).



Once you get the clutch and stater off you can employ the puller. It's right at the edge of not being able to work, so you need to be careful.




If you are careful the cases split right open. You might need to use a rubber hammer to get the transmission end to open up.


09-22-2015, 04:02 AM
The cases had some work done with port matching. Maybe to a Metrakit. I'm going to have to do some mods to the Airsal Xtreme to make it all line up. Since that requires noise that will have to wait until the morning. Thankfully it will be pretty straight forward work for the rotary tool.




09-22-2015, 09:02 PM
Had to wait for some day light to make noise with the rotary tool. First I slid the barrel onto the studs to see where adjustments would be required. Mostly I just want to remove any shelf that might disturb the flow of the fuel into the transfer ports. I feel that Airsal already knows more about port design than I do, and I just need to match things up.

Marked up with the Sharpe


I tend to take it slow, checking the work as I go. It's easy to remove material, and a bit harder to add material. Folks that do add tend to use epoxies like JB wield, or some such.



Almost there


I'm probably going to swap out the drive seal, and the shifter seal as well. The main drive seal is a 17x35x7, and the shifter is a 12x20x5. Lots of mopeds use the same size as the main seal for cranks (https://www.treatland.tv/SearchResults.asp?Search=17+35+7+seal). The shift seal can be found on some Hondas (part #91205-KF0-003) (http://www.partzilla.com/parts/detail/honda/HP-91205-KF0-003.html), and also on some KTMs (part #0760122050) (http://www.babbittsonline.com/oemparts/p/ktm/0760122050/shaft-seal-ring-12x20x5-b). Even O'Reily's has these online (http://www.oreillyauto.com/site/c/detail/BCA0/12X20X5.oap?ck=Search_12x20x5_-1_2745&keyword=12x20x5).



09-22-2015, 10:04 PM
Inspired by one of Matt's posts (http://www.apriliaforum.com/forums/showthread.php?311108-2005-RS50-Hybrid-project!-New-model-parts-on-a-old-bike&p=3928836&viewfull=1#post3928836) I decided to get the items necessary to build a leak down tester for this bike. O'Reily's has a large variatiy of rubber freeze plugs which are perfect for the job. That with a brass fitting, and that's basically all I needed. I already have a MityVac. ;)

With the Airsal Xtreme the exhaust port worked with a 1"-1 /8th" plug. The intake on this bike will be one of the Malossi units for a PWK carb. For this a 1 3/8th"-1 1/2" worked well.


Basically all I had to do was remove the bolt and washer from the larger one, and insert the brass fitting.


This fit nicely into the Malossi intake.



For the exhaust port it was just a simple insert.



And there you have it, a simple leak down test kit. I'll be testing this out once I get the engine built.


09-23-2015, 03:51 AM
you need to finish up the ports with sandpaper

09-23-2015, 07:03 AM
Yeah I did, but that's not in that photo. :P I'm still working on polishing the exhaust. My hands got tired so I had to stop for the day. :/

09-23-2015, 03:10 PM
I've been searching for an EGT solution so yesterday I called up the Trail Tech cats. They said that none of their meters were comparable with EGT sensors, because their temps didn't go high enough. From their website the TTO temp gage that we all use is ranged at: 30-500°F, 0-270°C. Which isn't nearly high enough for EGT.

The Trail Tech cat on the phone said that they would have to employ different technology to enable their gages to read EGT, and because they hardly ever get any requests for EGT it is unlikely that they will ever offer the ability.

The Stage6 EGT setup sells for around $100 at some places. $150 at others. It's basically a rebranded Koso, and Koso does sell a couple of different solutions, but the snowmobile folks don't speak too highly of these units.


The Sensor Connection has some real industrial equipment. The sensor would probably work (http://thesensorconnection.com/egt-probes/all-egt-probes/egt-probe-exhaust-gas-temperature-sensor-2-stoke-engines-18-diameter) for about $65 and shipping once you got all the bits you needed. And they have a handheld (http://thesensorconnection.com/thermocouples/electronics/2-channel-dual-mini-handheld-digital-thermocouple-pyrometer-thermometer-di) unit at ~$70 is in the ball park of many other inexpensive solutions.

http://thesensorconnection.com/sites/default/files/imagecache/product/product_files/product_images/EGT%20Probe_2S%20Series_2-Stroke_Exhaust%20Gas%20Temperature%20Sensor_90%20d egree_0.jpg http://thesensorconnection.com/sites/default/files/imagecache/product/product_files/product_images/HHMD-TIM-82N_Miniature%20Handheld%20Digital%20Dual%20Thermo couple%20Thermometer_Front.jpg

Another thing I'm looking into is an actual lambda sensor for strokers. But these are even bigger money.



Once you start thinking about this stuff all of a sudden something like the Aim Mycron4 (http://www.aimsports.com/products/mychron4/) shows up on the radar. This would be north of $400 so it's sort of pie in the sky at the moment. I think Matt has one of these, so I expect some education may be following soon. :P


09-23-2015, 05:47 PM
If you are looking at widebands I guess the new aem stuff is pretty good. I've always used innovate. Big problem is you will foul the sensor super quick.

09-23-2015, 11:31 PM
One of my bikes has the aim pista dash, the other has the Mychron 4 2t. They're basically the same thing

09-24-2015, 05:08 AM
The 4 2T keeps looking better the more I check it out. But I'm really not ready to take it to that level yet. But maybe by the time I get the bike running I'll be more open to the idea. If I had found the Stage6 EGT meter in town I would have gone that way this week. :P

I thought I'd be ready to drop the main bearings into the cases by now, but just too many other things have to happen first. I've got them prepping in the freezer.




I went by Treats to get the drive shaft seal. They didn't have a shift shaft seal. I'll have to source that from another vender.


09-24-2015, 11:50 AM
are you going to slip fit the crank first ? are the aftermarket cranks slip fit from the factory?

09-24-2015, 12:44 PM
Hi Matt, I'm not sure what you mean by slip fit. The general procedure that I've done in the past is install the bearings into the cases, put the crank into the bearings to where they stop, and then tighten up the case bolts. At least that's what I remember without reviewing the docs--which I'll do before assembly. What do you generally do? Another thing I have to verify, because I've forgotten, is which way to place the bearings. The crank that was in the engine looks to have had the bearings put on incorrectly. I say this because they aren't both the same. So I have some reading in my future. :P

09-24-2015, 12:48 PM
The Barn shipment showed up this morning. :D









09-24-2015, 12:56 PM
Basically the crankshaft journal is usually around 0.0002-0.0005 larger than the size of the bearing journal. So you resize the crankshaft with some Emory paper to where it gets to 0.0003-0.0005 smaller than the bearings. Now the cases go together much nicer and easier and you can also split them easily if you need to work on the gearbox. For what we do the longevity isn't affected although you might not get 40,000 miles out of a crankshaft this way, it will certainly last a year or two on a crank or multiple top ends and big ends on the connecting rod

09-25-2015, 07:59 PM
Thanks for the info Matt. If I had a lath I'd probably give that a go. Without one though I don't trust my hand sanding ability to do it properly. :P

I thought I was making great progress today. Finished up with a bunch of the cleaning last night and had planed to do the assembly today. Everything was going well, and got it the main cases buttoned up. The cranks spins nice and smooth, but the transmission doesn't want to spin well in fifth, and wont go into sixth. I hadn't taken the trany bits apart so I didn't expect this to be an issue. But really since there were signs that this engine had been opened previously should have given me pause to do a proper inspection.

The Heat! This is pretty much the only kind of gun I have--I say pretty much because there's a glue gun around here somewhere too. :P


The bearings dropped in.


Checking the new gasket.



The crank sitting in the new bearing before full insertion.



Almost time to put it together.


The sexy new Malossi drive shaft seal.


The manual states to make sure the bolts are all clean. This is the before shot, and they aren't too bad, but I did some cleaning on them anyway. The torque setting on these bolts is 6NM, or about 53 inch pounds.


All together, and waiting to come apart.


09-26-2015, 01:30 AM
are you spinning both shafts when you try to switch gears and have it completely vertical?

I slip fit the cranks by hand. No lathe, just V-blocks

09-26-2015, 02:39 AM
Yeah I took it apart, and cleaned it all out. Then made sure by the docs it was all together correctly. It's working now. :)

Sadly due to my current circumstances I don't have access to the usual tool action. Notice I'm working on the kitchen table. :P


09-26-2015, 10:47 PM
Made a little progress today, but I'm waiting on some tools to return, and that's slowed me down a bit. So I decided to put some of the pieces together to see hows it's going to look. :P







09-27-2015, 08:25 AM
So my doopler endurance 39mm wouldnt work with the xtreme kit damn..... 39mm to 40mm would it work or is it a marketing ploy i mean 1mm really ? Thats a gasket ahaha

Considering going for this kit on my am6 id be interested in what itd be like to "deal with" on the road when yours is complete a write up on the kit would be greatly apreciated

09-28-2015, 09:05 AM
Very nice looking, so clean and new! Tora so why was the 45mm stroke engine not so happy? I'll probably get back to work on mine, I have the jets now to get back to work on it.

09-28-2015, 01:59 PM
Matt, the stock stroke on the AM6 employs the shorter dimension of making a not quite 50cc engine. The Derbi EBE/EBS/DB engines use the 40mm dimension. To make a "fifty" they actually have to come in just under 50cc, because of regulations. They can call it a 50, but the actual displacement has to be just under 50cc. Derbi put the longer dimension in the stroke, Minarelli put it in the bore. But the folks that make BBKs, and cranks know this so you don't have to worry about it. ;)

Scotty, I haven't yet opened up the stroker engine to find out. I just put together a leak down kit which I intend to employ on that engine once the MityVac returns (it was loaned out). Guess I need to make a soapy water solution for testing too. Once I do the leak down test I'll use that information for further study. I suspect there is an air leak in the cases that's causing a lean situation that contributes to an overly hot combustion chamber resulting in seizure. But that's just my current hypothesis. I need to do some testing, and inspecting to find out. This is also why I'm so interested in the EGT and lambda sensors. I really want to know what's going on with these engines so that I can avoid the future seizing action.

Thanks for the nice words on the cleaning. It takes a huge amount of time to do it. :lol:

09-28-2015, 03:19 PM
Question about your RPM pickup on the DB motors. Does it use a RPM gear like the AM6 or is it a signal pickup? Im trying to see if I should keep my stock guages or go rs4 stuff but I dont know how to get the input.

09-28-2015, 05:26 PM
Hey D,

Funny I just posted this in your thread. The older Derbi engines did employ a gear off of the crank. But in 2002 I think it was they went to an electric pickup tach. It simply has a wire that wraps around the plug lead. Some gauges have you plug into the trigger that connect to the coil. On page one of this thread I posted an image of the MyChron4. I'm seriously considering this as a dash replacement on this bike because it has the sensors I want, and with the GPS unit it can do speed as well. Plus it is a data logger. Lots of good info could be collected. Imagine being able to corollate (after your ride) the temps, RPM, and rates of your favorite roads. The only thing I think it's missing is some sort of barometer, and lambda sensor. But you could look up what the conditions were for that day, and maybe there's a lambda solution. Koso makes a lambda pickup that's specific for two strokes (http://kosonorthamerica.com/instructions/BA029001.pdf). But I'm still in the research phase for that unit. Matt's got the MyChron already, so we can pick his brain about it. :lol:

09-30-2015, 01:53 AM
It's a strange feeling when you search for help on the web, and your posts on how to do things are the closest you find. :eek:

Today, with the help of my friend Ed, we cracked an important Euro2 Derbi engine secret. There are two versions of of these engines. One that has a balancer, and one that doe not. The balanced engine has markings on the gears to indicate how to set things so that the balancer is properly aligned with the crank. All of the performance cranks I've ever seen for the Derbi engine are designed for the non-balanced engine.

Now let me quickly state that when I say balanced in this context I'm not talking about machining the crank so that it is itself balanced. You could, and would probably benefit from doing that with either engine.

Here's a stock GPR balanced crank from the clutch side.


Here's the Airsal crank.


And a stock Senda non-balanced engine crank


By comparing these you'll notice that the balanced crank features a stepped design, while the non-balanced cranks feature a taper design. It may be a little difficult to see with these phone photos. My apologies.

Here are the two different primary drive gears for these cranks. The one on the left is the stepped design (I believe it to be Derbi part #00H02610381), and features a notch on the top of the gear, and a woodruff key slot. Notice that the taper gear on the right (I believe it to be Derbi part #00H02601381) features neither of these items. Yes you will need to source one of the taper gears if you upgrade your crank on one of the balanced engines (which is why I included the part numbers).


If you have a Senda with a non-balanced engine, and you upgrade your crank you'll not run into this issue. But if you have a GPR which features a balanced engine you will run into an issue when you go to set the alignment for the balancer, because there is no mark on the gear.

Ordinarily what you would do is set the balancer to align with the case mark, the mark on the balancer gear like this:


Then you would turn the crank so that the notch on the gear aligned with this mark, but now you cannot because there is no mark on the gear. What do you do?


Well as it turns out it's pretty easy. Aligning to that mark would actually just set the crank to TDC (top dead center). So all you have to do is set the balancer to its mark, set the crank to TDC, and then set the clutch basket into place. Mystery solved. :)


09-30-2015, 08:13 AM
Nice work on the balancer. depending on the weight of your reciprocating assembly, it's stroke, and it's operating rpm, as well as the angle it is mounted in the engine, you can experiment with phasing the balancer to see when it is the smoothest in the powerband.

My guess is that it will always be smoothest to the factory setting, because vector summation, but you can be surprised at times.

If you run a longer stroke and a larger bore piston which will obviously increase the mass, you can experiment with machining the balancer, and pressing in tungsten inserts which will make the balancer have a greater effect vs the first order vibrations of the larger recriprocating mass it is trying to damp.

i would absolutely always run a balancer if given the opportunity. I'm building a 500cc single right now with a balancer for a road race bike. you know, some day, when i'm home for more than 16 hours at a time.

leak testing

buy yourself a bottle of Snoop and never look back

09-30-2015, 09:19 AM
It's a strange feeling when you search for help on the web, and your posts on how to do things are the closest you find. :eek:
I know the feeling! But seriously, thanks for all the project updates. The technical detail and photos are really insightful and gives us hobbyists inspiration to follow in your footsteps with our own projects.

09-30-2015, 04:08 PM
I've set the balancer wrong before, and it made the bike unridable. On my EBE075 engine I had to replace the shifter mechanism. This required removing the clutch basket. I was very new to these engines, and didn't yet have the proper docs. Paz was the test rider, and rode the bike for a whole day. When we got back to my place I took it for a spin. I couldn't believe how much it vibrated. I asked him about it. His response was he thought that was normal for the Derbi! Damn Aprilia riders! :lol:

Anyway, after that I did some research, and started to get the balance right. ;)

That snoop stuff looks pretty cool. I'm probably just going to head down to the Dollar Store, and pick up some kid's bubbles for now. Later I'll try out the snoop. But I've got a slightly bigger issue to deal with for my leak testing. It turns out the MityVac I bought is unidirectional. It will only suck. :( I can use my bicycle pump as it's high volume low pressure, and can easily do the required 6psi, but I'll have to come up with a different connection to the leak plugs.

The main reason Ed came over last night was because I was tearing up all the gear pullers. The pinion just didn't want to come off. I had tried heat, and a hammer to break up the static friction. But I was getting nowhere. Ed brought over some high end snapon action, and we proceeded to chew up his puller. The nice thing about the snapon puller is that it had a good surface for hammering. It doesn't take a lot of force with the hammer to switch the static to kinetic, but it took about 20 blows to accomplish it. Today I discovered why it was probably so difficult. The torque setting for the pinion is 8 to 10 Nm. Yeah almost nothing. The person that had previously worked on the engine probably torqued it to 30 or 40 Nm. The thing is it's not the nut that holds the pinion in place, it's the taper. The nut simply creates the correct amount of friction. Such a classic wrenching mistake.

So lets help fix this situation with even more technical detail. :) Here are the Derbi Torque Specs!



09-30-2015, 08:36 PM
Need a Special Tool?
Getting creative with solutions is part of the tuners tool kit. Lets say that you want to torque the clutch basket bolt. The setting is suppose to be between 35 and 45 Nm. That's a fair amount of force. But lets say that you don't have the custom tool to hold the clutch in place. Here's what you can do. The output shaft can be held with a 16mm six point socket. The transmission needs to be put in gear. The nut on the basket is a 19mm. If you turn the nut, and hold the output shaft the engine will spin. A good size screw driver placed in the forward engine mount such that it rests on the wrench holding the output shaft will keep the engine from spinning. Thus the nut can be brought to full torque all without any of the special tools.


Setting up the Clutch
When you place the clutch disc in the basket make sure the labels face outward.


The next point of interest is this mark on the basket.


When you place the face plate on the basket line up the Derbi logo with the mark on the basket.


10-01-2015, 02:22 AM
Cheers so alll these updates, yesterday due to me finally getting annyed eith my clutch slipping i decide to buy dome stiffer springs
my clone am6 is slightly different oviously like it has 5 clutch springs
so i had to buy 2 packs of 4 -_- if only i could of waited another day aha another interesting thing about the clone is that the exhaust mounting uses bolts instead of the springs but whats great is the bolt paterns the same as tge db050 ( my airsal has the bolt patern aswell)
Back to tge point in hand damn....... 2 packs -_-

10-01-2015, 03:26 AM
When I assemble an engine I like to use grease to lube up all the bits. The piston, wrist pin, little end bearing, gaskets, o-rings. Pretty much everything get a bit of grease. Shops sell engine building grease for this purpose. It helps with the sealing, and protects the parts during assembly, and first startup.

Prepping for assembly. Polished up exhaust port.


Trimming the base gasket.


Bridge cooling holes in the piston (the drill slipped on the middle whole opps!).


Okay time to put on the top. This is a method I learned from the Moped cats. First you put the clip into one side of the piston (the side you wont be sliding the wrist pin into initially. Then slip the piston into the cylinder.


Then partially slide in the wrist pin to the edge of the first side of the piston leaving room for the crank, and little end bearing (you can do this step pin in before putting the piston into the cylinder).


Next rotate the crank to TDC, and carefully slid the cylinder onto the studs to the point where the wrist pin lines up with the little end of the crank with the wrist pin bearing already in it.


This next step is crucial! Once the cylinder is sitting there with the pin through the bearing waiting for the other clip to be inserted take a clean rag, and cover up the area below the piston. If you drop a clip into the crank case you might have to split the cases to get it out. It's much easier to cover it up with a rag.


Then insert the second clip.


After that the cylinder can be lowered down to the base gasket. I then like to check to make sure the piston isn't above the bottom of the ports when at BDC (bottom dead center).


Then place in the o-rings.


Then place on the head (it has it's own o-ring that you need to put on first--here the grease helps keep it in place when you flip the head into position).


Add the washers and nuts, and tighten to around 10-12 Nm using a cross pattern slowly from one stud to the next. Do this repeatedly until all the nuts are at the proper torque. It's important to not tighten one down all the way, and then go to the next. You could damage something that way, and you probably wont get a good seal.


10-01-2015, 03:51 AM
I have to say I was excited to get to this step. I've been looking forward to it for quite a while--ever since Matt first posted about it in (I think) Drac's thread.

I had already built a leak down test kit. But it wasn't going to work because the MityVac that I bought (sometime ago now) only does vacuum. They make a MityVac that can do both, but I didn't get that one. :eek: So I had to make a mod. I removed the brass fitting and employed a new valve stem that I had bought for another project, but didn't use because I could only get one of them.


I also made a stop at the Dollar Store today to get some bubbles. They only have the humungous version--32oz! I probably wont be needing any Snoop for quite a while. My roommate had never seen bubbles before so we had a grand time making them all over the kitchen--it's going to real easy to wash the floor next time. :lol:


I then hooked up the bicycle pump, only to find the system didn't hold pressure at all. It turns out that the exhaust studs on the Airsal Xtreme actually go into the passages. This was good to find out so that when I install the exhaust I'll employ sealant on the studs. So I popped in some studs temporarily, and tried it again. This time there was pressure, but as you can see this helped prove the validity of the Bubbles solution as an effective tool.


I also found a small leakage where I apparently didn't trip the case gasket well enough for the intake manifold to make a proper seal. Previously I would have missed this issue which would make tuning a pain in the ass, and likely as not cause a lean issue at some point--which could contribute to frying the engine. I really feel like I'm upping my game. :)


Don't worry Scotty, I'm going the be trying this out on the 45mm stroked engine soon. :D

10-01-2015, 04:12 AM
Right, lots of posting today. You'd think that I've made great progress, and will soon be putting the engine into the bike. Well you'd be wrong. First I discovered that the RCS that I got was for 1" bars. Yup Harley action. Oh well. I'm not quite ready to install them, so the replacement will probably be here before I'm ready for it. :lol:

Next I thought the tranny was messed up again. The engine was doing that only turn so much, and then stopping thing again. I was almost convinced that it was the transfer gear. But I was wrong. I put my ear on the head, and I could hear the knocking. It was ever so slight, and not even enough unless the head was bolted down. If the head is just sitting there the o-rings lift it enough that there is no contact. Wow.

When I got this kit it was sort of a bastard. The box made claim that it was for a Euro3. But clearly the cylinder is for the Euro2. So I bought it. The cylinder works fine on the engine. Everything lines up. But the head is drilled with different dimensions. This didn't matter though, because I have a bunch of Airsal heads. :roll eyes:


Or so I thought. It turns out the 45mm Xtreme heads extend deeper into the cylinder than the 40mm stroked Xtreme heads. Here check them out.



And as you can see here there just isn't enough room for that much insertion.


So I could deck the head to the point that it didn't insert as much, but then the profile would be changed, which would dramatically effect the squish. I could use a bunch of base gaskets, until there was enough room, but that would kind of mess-up the transfer ports as the piston would be below where it should be for these port designs. This is one of those things that proves you should have your own personal lath hanging around.

10-01-2015, 07:19 AM
I agree that decking the head would mess up your squish. If you machine the head so it doesn't protrude so far into the cylinder while maintaining the same squish band and semi-hemispherical combustion chamber shape then you'll also need to space your spark plug so it doesn't reach too far into the cylinder. That isn't a big deal since you're probably already using some sort of spacer to index the spark plug in the ideal orientation anyways. I do worry about machining the head too thin but without the parts actually in hand it's hard to say how much can safely be removed. I'm a hack machinist but there are a few different paths you can take to get the semi-hemispherical shape using a manual lathe. If you have enough swing then you can mount your tool to a rotary table but rigidity may be an issue. Or you can make some sort of contraption like this (http://s625.photobucket.com/user/rbehner/media/Bendix%20PBS/pbs1.jpg.html?sort=6&o=0). A CNC lathe would be no problem. You can also achieve it with a vertical mill, rotary table, a fly cutter and some math.

10-01-2015, 04:21 PM
That airsal kit has a head gasket the way I expect them to be on all 2 strokes with o right head gaskets.

My flipping top performance and athena both had the stupid o rings and head gasket on the cylinder head instead of the cylinder.

Made for some awkwardness as the bloody thing kept falling out.

All I can say is arse hole for your head problem. I'd use base gaskets myself as I'm a tight wadd.

That would really piss me off finding that, I hate it when things don't go to plan.

10-01-2015, 05:36 PM
Yeah things rarely go as planed! I guess I'm kind of use to that these days. :/

I went over to Treats today. Benji is going to get the proper head for it for me from Airsal. :) Yeah Benji!!! In the mean time I'm going to try two different things. Base gaskets, and look at the 45mm stroked engine. Benji hooked me up with a very attractive offer on the 45mm stroked kit. Lets hope #4 is a winner!

GLI, JP did some machining on a head for me on the Cagiva when I got the 150cc kit for it. He made a ring just like you are talking about--I'm sure he could do the same thing for this head, but since Benji can get me the proper one I might as well wait for it. I have a bunch of base gaskets laying around so I might as well give that a shot. If it doesn't look viable I can wait for the proper one to show up. In the mean time I'll build up the stroked engine. :P

By the way Benji has an Xtreme kit in stock for the Euro3 engine (http://www.treatland.tv/airsal-T7-racing-Xtreme-80cc-50mm-cylinder-kit-p/airsal-derbi-senda-010810050.htm) (it's got all the proper stuff, I checked). It's the 40mm stroke version so it will work with most any stock lengthen crank. If you have a Euro3 engine I'm pretty sure he'd give you a good deal on it. Either contact him directly, or let me know, and I'll help you.

10-01-2015, 09:55 PM
I gathered up a bunch of base gaskets, and tried them out. I've left my solder at a friend's place so I can't yet do a squish test. That will have to wait. But the piston is sitting at about the right place at BDC so there is hope!





The only concern would be if it was more likely to develop an air leak at the base gasket. I've run into that issue previously. Case in point. I pulled out the 45mm stroke engine, and got the leak down test kit in play. The only place it is leaking is at the base gasket. It's doing this on both sides. This is with a Metrakit top end made for a 43mm stroke that I adjusted to work (it didn't work) with a 45mm stroke crank. This was one of those, well what do I have around experiments. :lol:

The good news though is that it's not leaking at the cases. So maybe the issues is something that I can address without splitting the cases. It will require further investigation.


10-01-2015, 11:16 PM
Well Scotty I'm getting the information you requested! But first a quick look at the 40mm kit. With all the gaskets I'm getting a small leak at the back of the base gasket. I'm hoping that I'll be able to work on that, and fix it.


Okay now for the 45mm kit. It was difficult to photograph this because to get enough light on the subject the camera would strobe. But you can see oil in the bottom of the crank case. I suspect that this is trany oil. So yeah I'm probably going to have to split the cases to find out more. Ouch! :eek:



10-02-2015, 02:17 AM
Bit of gasket sealant on the Base gasket top and bottom, not much just a smear should help with that leak.

Is it not possible to do the crank seals without splitting the crank cases? I can do mine on the am6 although they are a pain to get out.

10-02-2015, 01:06 PM
Hey Tom, yes if it is the main seals--you can change them out by removing the clutch cover, the clutch, pinion gear, and on the other side the stator/flywheel. But in this case if it was a bad main seal letting in the oil it would be on the clutch side. However, my current hypothesis is that on the 45mm stroke engine the gasket has failed, and that's what is allowing oil into the crank case. I suspect this because we had to remove some material to allow for the crank. We may have removed too much. Let me see if I can find a photo...okay it's in this photo, but hard to see. Anyway, I'll check the main seal on the clutch side before I split the cases on this engine.


For the 40mm stroked engine I was able to do a squish test. It was way too close. So I added more gaskets. I can get enough squish if I use multiple metal gaskets, but then I get leaks. Based on all the leaky action I've been finding I wonder how I ever built anything that ran previously. I am so glad that Matt posted about the leak down test kit. Plus, now I get to play with bubbles. :lover:

10-02-2015, 02:48 PM
Now imagine sealing a v4...

I too struggle with base gasket leaks

Permatex RTV Ultra Grey should be available at most auto parts stores, it's awesome
the Threebond grey that treats sells works well also
Toyota black silicon is excellent

RTV, a torque wrench, multiple steps of torque, and new studs might help you get the sealing correct.

Also, set your squish to 0.030"

10-02-2015, 04:02 PM
I've got the squish about as close as I'm going to get it with this setup. I think it's a bit much, but it will have to do until the proper head shows up. :)

I've also got the leaks stopped. I did break down and employ some sealant. :) I will probably get the rest of the engine together today. :D

I did notice that the clutch basket seemed loose. I have a basket off the Senda (I have a Senda project too) that isn't loose, but it's not on the engine. So I opened up the 45mm stroke engine's clutch case to see if it is indeed how the baskets sit when installed, and sure enough that one was loose too.

With the clutch cover off I did discover more evidence that it could be a bad main seal on that engine. Check out all the junk in the oil. I wont really know for sure though unless I do more tests. I'm considering putting on a top end to do a pressure test, but I'm fairly certain that I'm going to have to split the cases on this engine.







10-02-2015, 09:02 PM
I'm a quite sick of leaks.

Brand new gasket on the water pump, spent time cleaning the surfaces and I'm given a leak.

Glad I have plenty of sealant.

After seeing your leak test showing the leaks at the inletmanifold/reed valve I built mine up with a thin smear of sealant on each layer.

All this messing about and I've only had it in first and second whilst running, really want to see if the gearbox is stable shifting through the gears whilst running.

Good luck in finding the oil leak. I'm praying mine is cured.

10-02-2015, 10:25 PM
Matt I can't believe how much good data I'm collecting with the leak down tester action.

Tonight I got the the Monza engine out for a check. It seized on a ride a few Sundays ago. The entire time I've had this bike I've never been able to get it to run right. Well there's a big wow, and I found it with the leak tester.

Here's the plug. It looks okay.


The bottom of the piston. There's some discoloration, but it's not that burnt.


The piston broke up at the ring pin, but the seize wasn't that bad. I will probably be able to clean it out with some muriatic acid.


When I did the leak test I found three places where it was leaking. On top where the carb is just below the cylinder at the case split, and in the same place below at the case split. The third one, well...




Check out this pin hole. How could something like this even happen?



The previous owner did quite a bodge job on the cases. Two of the case screws have been exposed to the crank case. I've always thought this was the big issue with this engine, and it is a problem. If I don't put sealant all over these bolts (yeah stock they are screws, but I replaced them with bolts). But even putting sealant on the bolts didn't halt the problem. But it didn't make any sense.



Hmm...I don't have a good photo, but it turns out that the previous owner did some sort of epoxy JB action to deal with going through the cases. This bondo job seems to have failed enough to create a crack or something, and developed a leak. As we can see from the bubble evidence. Now I have to figure out how to fix it. I'm thinking sourcing new cases might be the best way to go, rather than trying to repair the mess left over from the previous owner.


10-02-2015, 11:41 PM
A whole lotta bubbles going on!

10-02-2015, 11:46 PM
Dude, jb weld the fuck out of it, it will hold

i ported my derbi revolution cases so much i went clear through the transfer.

i felt like such an idiot. i was so embarassed. i had never even had a revolution before, i'd had way too many coors lites, and i was hell bent on getting the metrakit 70 installed on this revolution. i wanted to make the transfers as large as possible. I literally did. i made them too large. as large as they could possibly go, and then some, putting a pinhole through the case. I taped the inside of the case up, and then basically reinforced the entire back side with jb weld and steel wool mixed together.

it held like a champion

10-03-2015, 07:16 AM
Really interested to see that the Derbi engine uses a crankcase gasket.
The AM6 doesn't.
At least none were included in the full gasket kit that I purchased, and no gasket was present when stripped.

I flatted the crankcase high spots on a ground marble table, and assembled with copper grease.
The motor runs well, but after seeing all your leaks...... perhaps a bubble mix test might be useful.


10-03-2015, 09:03 AM
I'm blaming you tora.

Decided to work on the 86 motor, started it up to find a slight leak coming from the Base gasket.

You jinxed me from all of your leak down tests.

Engine currently in bits awaiting sealant to cure.

10-03-2015, 10:25 AM
You guys wonder why my bikes run well and I'm never posting about them blowing up? Well there's your answer in tora's thread lol. Fix your air leaks

10-03-2015, 12:32 PM
Hey Tom,

Yeah I think credit is a better word than blame in this case. But it also has to go to Matt for posting about the leak test action. It's one thing to blow up a kit because you are pushing it to win a race, or some such, but it totally sucks to lose it due to some lame ass air leak. The Track Bike is next on the list to get tested, but it's over at Ed's so it will have to wait. I suspect, with the exception of the intake manifold which I know is suspect, that the PPMPR engine (http://www.apriliaforum.com/forums/showthread.php?310473-Project-Poor-Man-s-Pro-Race) doesn't have any leaks. I say this because it's been a very stable good running engine. :P

I am also pretty convinced that there's going to be a MyChron42T. This will mean that the plastics will have to wait even longer to be ordered, but I really want to make sure things are running properly. And it looks like getting the Koso two stroke lambda sensor bung with one of the lambda sensor kits is in order too. It doesn't look like there's a lambda unit available for the MyChron, but the one lambda sensor can send out data, and maybe that data could be sent to the MyChron for tracking. With that setup one could then have EGT, CHT/H2O, and lambda tracking. Those three data points would give you some pretty serious information. I'm going to have to source a good MyChron dealer. There's a kart shop in SJ called Cambrian (http://cambriangokarts.com/store/filtered/d_1/d_1/c_32/). They sell the MyChron, and might be a good source--but damn it this stuff is expensive. I've also seen them on eBay, and Summit has them.

10-03-2015, 01:17 PM
I'm now lining every gasket with a thin smear of sealant to fix any potential leaks before they happen, prevention is better than a cure I hear.

The 86 is sweet now, just needs playing with the jets to get it a bit smoother.

10-03-2015, 02:40 PM
You need the e box multiplexer with the lamda controller and then you can do it

I don't think I'm going to log O2 anytime soon, they have it at the dyno

I buy all my aim sports stuff from Pegasus

10-04-2015, 04:03 AM
I think I'm suffering sticker shock with the MyChron. When you start adding up all the little bits it could quickly add up to over a grand! This has got me thinking that maybe there's some other possibility. When it was a $300 device it looked quite attractive. :P

I'm coming to the point that the engine is going to be complete.





One issue that's been bugging me is the stator plate for the Puch when placed on the Derbi there's no room to move it. The timing must be set by placing the flywheel on the crank. Not very friendly. I'm going to have to see if HPI makes a plate for the Derbi Euro2 engine.



I picked up a Polini PWK for the moped, but now since it's in limbo I may just put the carb on this engine.


10-04-2015, 08:30 AM
just get the programmable CDI box, and adjust the timing with keyboard strikes instead of screwdriver turns

10-05-2015, 03:42 AM
Yeah the programable box is on the list, but the list is long, and it takes a long time for things on the list to appear. :P

I went ahead and did the install based on the the online HPI docs (http://www.hpi.be/downloads/210_1C_130_eng.pdf). The Derbi engine turns counter clockwise, so the mark on the left of the stator is the one that gets lined up with the mark on the rotor, once you set the crank such that the piston is 2mm below TDC.





The nice thing is I'm getting to the point where I'll get to play with some nice toys like the Jolly Moto. I picked this up off of eBay a long time ago. I don't know how it will like running with a kit this big though. Ideally I would get a more appropriate Jolly Moto, but well that's just not going to happen any time soon. This one had been boogered up a little bit, but it should be fine.




Another thing I found in the stash is the Daytona temp meter. I don't have the sensor for it though. I tried the Koso sensor since it has the same connector, but it seems to be incompatible. The nice thing though is that it came with an adaptor. Maybe the TTO Trail Tech sensor will match up with it. ;)





10-05-2015, 01:36 PM
My moped buddy Tyler put together a neat little calculator (http://www.mopedspreadsheet.com/ignition.php?stroke=40&length=90) for converting mm from TDC to degrees of rotation. You need to know the stroke, and con rod length. For the Derbi type engines (http://www.mitaka.co.uk/ROAD_BIKE_RODS/OTHERS/BA162.htm) that's 40mm, and 90mm.

The docs for the HPI suggest 2mm before TCD, which is roughly 23.5° of rotation. This information becomes handy if you decide to check your mechanical timing settings with a timing light. Tyler suggests doing so with the HPI mini rotor because he's seen the markings on the flywheel to be way off.

10-05-2015, 03:44 PM
Okay, an area where I have much learning to do is with the ignition. I understand the basic concepts, but that's not enough for really tuning this stuff to the level that I want to achieve. Like Matt suggested previously I need to get the programable version of the HPI kit. That's actually one of the reasons I've invested so heavily in HPI--you can program it. ;)

Here's the ignition curve of the HPI.


The stock setup is to have the Derbi engine set to about 23° BTDC (before top dead center). But how does this compare to where the engine gets on the pipe, and peak power, because isn't that where you want to set up the curve to function? Well I don't have the data on this engine to know. This is a new combination for me. But I do have what I ran previously on this bike. Norcal Cycles does an annual dyno day. It's a blast. lots of different bikes show up. I'm of course the only goof ball to show up with a two stroke. :lol:

Here's what the 45mm stroked Airsal Xtreme did with a 24mm PWK, Metrakit ProRace, and the HPI set at 2mm BTDC. From this chart, and by looking at the curve chart we can read that at peak power ~13.5K the bike had ~5° of advance, and at ~9K where the bike starts getting on the pipe there was ~15° of advance. Which my friend Tyler should be ~16° of advance when the bike gets on the pipe, and 20° at about a 1K idle.

Tyler also mentioned that the HPI mini rotors that he's worked with should be checked with a timing light, because he's found that the markings aren't particularly accurate. So all of these readings should be somewhat suspect, because I set everything mechanically, and didn't run it with a timing light. I didn't know that the mini rotor had this feature. :eek:


And because you'll want some sexy, here's what the bike looked like that day.



And what the ignition was set to on the bike.



2mm BDTC


Interesting how the older version of the HPI had a different plate.


10-05-2015, 10:03 PM
you want peak power to have 15 degrees of timing

you can make so much more power by putting more timing in that thing

10-06-2015, 08:55 PM
Tyler told me that the markings on the HPI 2Ten mini rotor are not dependable, and that it's best to set it mechanically at first, and then check it with a timing light. Now I have the engine assembled, but not installed so I haven't checked it with a light, but I've been reading about lights. This is sort of bad news. Our engines don't even act as if their are on until 5, 6, or 7K. The 45mm stroked engine didn't get on the pipe until 9K, and it peaked at around 13.5K.

Looking at the timing lights even the MSD $220 timing light is only rated to 5K rpm. Which is to say you can check the idle, but you are not going to be able to accurately check the advanced timing.


10-06-2015, 10:15 PM
you set the base timing because you know what it is, and then if you know the curve (which you have above), then you know what the timing is.

10-07-2015, 08:17 AM
My Equus timing light goes up to 9,990 rpm but what Matt said is generally how it's done.

10-07-2015, 03:27 PM
looking at that timing curve here is what I would do.

1) make timing marks on the flywheel for 35btdc to 0btdc (every 5 deg)
2) adjust the slide stop / idle screw until you get an idle of 4500
3) start the bike and idle (@4500)
4) turn on the timing light and shoot the flywheel
5) adjust stator until you're shooting 30 degrees. that will give you enough timing up top.

10-07-2015, 03:31 PM
make sure you're enabling the blue curve above

10-07-2015, 03:55 PM
Thanks Matt. I'm a ways away from from starting it up. I don't yet know how to get it set to the second (blue) curve. I think there's some added gadget that you have to get to do so, but I'll send Willy at HPI a post to ask him about it.

I did want to ask you about something though. With the suggested settings, and the original (red) curve the bike would be at around 5° advanced at peak power (13.5K rpm). My understandings is that with a stroker less advanced creates hotter gasses sent into the pipe, which because they are hotter they travel faster, matching the higher RPM, producing a better "super charging" effect. If I'm understanding you correctly, and reading the chart correctly, wouldn't I be seeing about 17° at 13.5K rpm? Shouldn't it be less advanced near the top for the hotter gasses?

Oh and sadly I can't adjust the stator. It's on where it's on. Any adjustments have to be made by taking off the flywheel, and placing it in a new position. Which is a real pain in the ass, and difficult to be precise. I've asked Willy if they have a more appropriate plate for the Derbi, since I'm currently using the Puch plate.

I'm currently working on the chassis. Mostly just cleaning parts. It's a lot of work to clean this stuff. The really great news though is I finally found the box with the chain adjusters. :D I was really worried about not finding those suckers, because I've never seen them on the eBay, and to order them could take 6 to 8 weeks! :eek:


10-07-2015, 09:33 PM
for the red curve

1) make timing marks on the flywheel for 35btdc to 0btdc (every 5 deg)
2) adjust the slide stop / idle screw until you get an idle of 3800 You do not have nearly as much leeway in this because there isn't hardly a belly of dwell in the red curve compared to the blue.
3) start the bike and idle (@3800)
4) turn on the timing light and shoot the flywheel
5) remove that top bolt from the stator because the slot is in the wrong direction from the other two. adjust stator until you're shooting 30 degrees. that will give you better timing up top. you should be running around 11-12 degrees or so it looks like at 13k, and 10 at 13,5.

if your bike is set up right you can run 15 degrees at peak power, and taper it off afterwards to widen the powerband and add to overrev. like you said, make the combustion event happen in the pipe so that it burns hotter and you can boost the operating range of the pipe. likewise, before the max power and efficiency of the pipe, you want to have slightly cooler temperatures which shifts the optimum operation of the pipe to a lower rpm. a gross perversion of this is the water injection honda used on their gp bikes in the 90s.

so you know you want 15 degrees at peak power, whenever that is. set your base timing all the way to 15 degrees flat and do a pull. note when the bike makes peak power. add more timing before that, and take timing out afterwards. you'll get some sort of a slope. generally you can run almost totally flat /more advanced timing, basically your " full advance " from say, 4000 rpm all the way to say, 1000 rpm before the pipe begins to work, so say 8000-9000. from 9000-peak power you will begin your taper to 15 degrees, hitting 15 at peak power. then after that you will roll off the timing even harder, usually. experiment with the timing to widen the powerband as much as possible, that's really all you're doing there.

the rsa ran like 30 degrees of timing or something crazy up until like 9000, and then it tapered down to 15 degrees at 13k when it made max power, and by 15k it was 6 degrees

your motor makes similar revs and power as the rsa, just copy that timing curve. put a zeel on your bike and call it a day

10-09-2015, 05:14 AM
Matt sweet post thanks much! Have you ridden an RSA? That must be a really fun bike. :D

Reading your post makes me want to step up to the HPI programable ignition even sooner than the current schedule. Oh my poor aching wallet! But first things first, got to get the bike back on the road. :lol: Man does it take forever to clean this stuff.

I did a bit of fiddling around. I'm going to be running 2003 front farings, and the stock tail section. Just parts of it for now. I have some plans, but it's going to take a while to realize. I also think I'm going to forgo the stock air box too.







10-09-2015, 12:54 PM
I haven't even seen on in person, unfortunately. they're still like 50,000€

10-09-2015, 05:14 PM
I haven't even seen on in person, unfortunately. they're still like 50,000€

While working on a Bats bike at CN racing back in 2013 a guy came buy with RSW parts for Carlos to fix. I was blessed by the gods of two strokes and granted one touch, with gloved hand, of a sacred Aprilia RSW cylinder!

10-09-2015, 05:29 PM
This may not work out as well as I had hoped. It looks like maybe the radiator is going to be a bit wide.











10-09-2015, 08:20 PM
Necked bikes have been your signature all these years, remember RRR, maybe the bike is trying to keep it real!

10-09-2015, 10:30 PM
use an rs50 early radiator (the double thickness one)

10-10-2015, 12:23 AM
Hi Matt,

I have one from the earlier GPR that I could use, but this is really a temporary solution until I can order a new set of plastics for the bike. I really don't like riding it without plastics, and I figured I should be able to get the bike running with what I have laying around. Then when the budget allows I can update parts on the bike as I go. So these plastics are just a temporary stage for the bike. I was going to wait until I had all the bits to do the bike the way I want to, but having the Red Bike (http://www.apriliaforum.com/forums/showthread.php?275584-Derbi-The-Red-Power) run over ten times has put me in a position where I need to get something active, and this seemed like the best way to go about it.

I found a place, LDC Productions, that that still makes fiberglass for my bike (http://www.ldc-productions.be/40-derbi-gpr-50-2004-2009l). When I can afford it I want to order these for this bike. Yes the list is very long! I also found a place, Red Racing Parts, that sells wind screens for these plastics (http://www.redracingparts.com/english/motorbikesmotorcycles/partsandaccessories/aeromaxwindscreenswindshields/derbi/GPR50125RacingRaceReplicaDiMeglio2004.php), but they don't have an image on their site. Oh wait they do of the black screen. :lol:

Big note on Red Racing Parts (https://www.redracingparts.com)
I ordered this screen and a Domino choke lever assembly from them on March 23rd 2016, and they charged me for the pleasure. Today it is May 26th (65 days later) I regularly email these guys about my order--I still have not received any shipments from them! Their communication only occurs when you prompt them. They send an auto reply that means nothing, and then maybe they get back to your email. They repeat the same stuff over and over, but it always seems to be some sort of stock error and the parts will ship in "10-12 days." Notice how they actually use the exact same words repeatedly! And of course the parts never ship. This is horrible customer service.

I should also note the day that I ordered these items they showed a discount on the screen. This discount changed while I was filling out my order to a lower discount. I contacted them about it, but they wouldn't do anything. This very much falls into the bait and switch category.

March 25th

Ok, we will ship asap.

April 15th

I'm sorry for delay. However, we will ship your stuff in 10-12 days.

April 18th

We had an error in our stock and we are doing our best to speed up.

May 9th

I'm sorry for delay. However, we will ship your stuff in 10-12 days.

May 10

We had an error in our stock and that is the reason of delay.

291182 291183

Dcrac3r reminded me about Hubert Cycles in France that also has some GPR body work (http://www.hubert-cycles.com/poly-course/212-carenage-derbi-aprilia-rs04-09-nud-gpr-3000302589019.html).


10-10-2015, 06:13 AM
I like the old style twin lamp one above the other fairings.

But the fairings that the bike should have are just a beaut, they are what always draw my attention to the gilera sc 125 and derbi gpr 125, it's more gilera sc you see around here though, i don't see many gpr 125 2 strokes going about.

10-10-2015, 12:37 PM
Hi Tom,

I agree the styling of these bikes is really special. I may try to do a vertical light array with the fiberglass when I eventually get to that point. The regular mounts for the stock lights are in the faring. They didn't build a structure to support the lights. So if I go fiberglass I'll have to create a support for the lights anyway. Matt pointed out the Foggy Petronas FP1 that the Derbi shares a lot of lines, and it had the stacked lights. So I might try something like that look.


10-11-2015, 07:19 PM
Had a chance to play around with the muriatic acid today. See kids this is why you want to take chemistry classes. Anyway, this is basically swimming pool acid, but it's still acid, and a fairly strong acid with regards to what you can just walk into a hardware store and buy. You need to be rather careful with it because it can really mess you up.

I should have gotten better before photos, but these are mid process photos, as this is the second pass. I did the first pass earlier in the week. Still you can see the magic of the acid action. This disc could probably benefit from at least one more pass, but I've had enough playing around with acid for today. The stuff, even when properly geared up is still nasty.






10-12-2015, 12:56 AM

Well a little bit of progress was made today. Through the clever and strategic application of zip ties I was able to complete the mounting of the tail section and seats.



How do these things get so dirty? Oh yeah I actually ride my bikes. :lol:




10-13-2015, 12:48 AM
Didn't make a whole lot of progress today, but got things a bit cleaner. :P



10-13-2015, 04:08 AM
The crash messed up a bunch of things on the bike. I'm ever so slowly finding the bits and replacing them. Today thanks to Dcrac3r (http://www.apriliaforum.com/forums/member.php?103103-Dcrac3r) I headed over to EasyParts (http://www.easyparts-rollerteile.de/choosedrawings/9/1660/BK/0-4019-1-m414-m1008-m2937-m24674-m1660-s22380/Genuine-Parts-Derbi-GPR-50-Racing-2004-2005-E2.html) to partially correct this situation--notice how the bar on the left is much shorter than the bar on the right? Because both bars were damaged I was able to use a left bar from an older GPR, but the older GPRs have shorter bars than employed on this bike. Makes for a really strange riding position.


EasyParts has the bars for just under $20 each after Euro to Dollar conversion, and the shipping wasn't too bad either. So a bar replacement is on the way, with a few other little tidbits. I really wanted to go for the floating vented front disc (http://www.easyparts-rollerteile.de/Brake-Disc-New-Generation-1103_(Genuine%20Parts)-p12334075.html), but at about $200 I really had to hold off. It sure is a sexy piece of kit though. :lol:



10-14-2015, 09:40 PM
Got to visit Treats today. I needed to grab a fuel filter, and a wee bit o hose. Now previously I had picked up the Malossi super purple petcock. It turns out that the fitting on the Malossi is 8mm which is much larger than the typical 5 or 6mm fittings. So to take advantage of this unit I would need to source a bigger fuel filter, and proper hose. Treats had what I needed. I went with the OMG filter, and some Motion Pro 6mm black line. I kind of wanted to get the Malossi clear 6mm line, but they had a scrap piece of the MP line--which was free! So I caved. The OMG filter has a clear window so I'll still be able to see what's going on. ;)

Interesting about the Malossi petcock--it takes nearly four full revolutions of the knob to open it up all the way. Seems like a pain in the ass, but then it is a racing item, and they tend to function a bit different than what you would employ on the street (even if you are ultimately putting it on a street bike). :lol:





10-14-2015, 11:54 PM
I was running into fuel starvation issues on my bikes and I found out a yamaha blaster petcock fits the Aprilia fuel tank almost perfectly.

10-16-2015, 02:22 PM
Yesterday I didn't get any work done on my bike. :eek: I got to hang out at Bolt seeing how they put together their bikes. Nate is presenting at a show this weekend, and they needed a one off skeleton bike to illustrate what it looks like underneath. :)



10-16-2015, 08:19 PM
Again today not a whole lot of progress, but a big step was accomplished. I finally started making brackets.:) I got held up though because I don't have the bolts, and spacers I need to progress. Not as pretty as I would have liked, but considering I don't have a shop they came out okay. ;)

These two brackets will hold the front faring support in place. There will be two lower mounting points too, but until I can get these properly mounted I can't take the measurements for the other brackets. It will all flow from these two. The first two photos were taken during a check to see how the first holes lined up. Then the third photos was checking the brackets with the faring support. Too short place holder screws with no spacers wasn't doing a good enough job to go forward.




10-18-2015, 05:38 AM

10-21-2015, 12:27 AM
I seem to be having trouble getting the right fittings to have proper function with the brackets. I need some spacers to make things function properly. I would like some metal one, but the hardware store only have nylon, and only 3mm too long. I figure I could file them down, but nope. Maybe with the rotary tool. And again I got slightly too short bolts. :/ But I can see the big picture, and it should be coming together soon. ;)





I did at least finally get the rear wheel installed. Mostly just had left over cleaning to do--the Motul polish really helps with the wheels. The previous hold up was finding the chain adjusters. :lol:


10-22-2015, 03:39 AM
Some many long time age Dante hooked me up with some Aprilia plastics from some race bikes that they once had a Scuderia. On one of them came this cool little gadget. It's purpose is to enable quick removal of the farings. I've seen them on some race bikes. This tube attaches on the faring, there is a rod that is attached to the bike. The tube fits over the rod, and an R clip holds it in place. As you can see the tube has a well nut on one end, and the bolt has a shoulder so that the faring isn't pinched. Pretty cool stuff. I've been trying to find these, but so far I can't seem to find a vender for this stuff. I did find something similar in FDG's CB350 build thread (that's how I found his thread), but that's the closest I've been able to find.


10-23-2015, 10:08 AM
It's purpose is to enable quick removal of the farings. I've seen them on some race bikes. This tube attaches on the faring, there is a rod that is attached to the bike. The tube fits over the rod, and an R clip holds it in place.


Or you can always roll your own if you've got a lathe or access to one. The ones on my CB350 are very well made from aluminum. Shouldn't be too hard to replicate.

10-23-2015, 10:42 AM
Actually these could come in very handy for my kit. Good stuff!

10-23-2015, 02:31 PM
Whoa Fibaa!


That is so cool!

Since I'm fashioning my own brackets anyway so I might as well figure out the tube thing. :lol: These Tyga units give me some ideas. The last trip to the hardware store I discovered that they stock R clips, well nuts, and other bits that are close to what I would need.

If I had a TIG welder I could use aluminum rod, and weld it to some aluminum plates that screw into the frame, replacing the stock plastic mounts that screw into the frame. Then have these tubes fit over them and R clip in. I could also just tap some threads into the end of the rod, and secure it to the brackets. That should do it.

I might even be able to fashion something up for in the belly pan so that I wouldn't need tools down there either. Then it's just figuring out something where the side panels connect to the top. Maybe a screw converted to an R clip could work there too. Something to think about. :)

10-23-2015, 07:44 PM
Easy Parts showed up today. It took longer than other people's orders because I ordered some stuff they didn't have in stock. But it came fairly quick. ;)



The important parts are the new bars to replace the ones that got messed up when I was crashed by the Honda Driver. I also got the rubber bushing for the front of the tanks since that was missing when I got the bike. I should have ordered the spacer that goes along with it. I'll have to fashion up something now. The other bits are the water pump gear for the crank, and a new nut and washer for the crank. The last item is new top end nuts. These things are for the Senda Project--some time in the future. :lol:


10-24-2015, 02:32 AM
The new bars came individually wrapped--like Japanese treats!


Because I didn't have the correct bars for the bike I employed bars from an older GPR, and well they had issues on this bike because they are quite a bit shorter.


Left and right bars use to have different part numbers. It had these things so that the holes that orient the controls have certain locations. But the new bars are designed to be for either side. This is the same bar just rotated about 30°.



Installing the bars.





10-24-2015, 09:19 AM
i had no idea that the derbi rear brake was mounted with its own linkage, that's very antiquated. i wonder why they did that

10-24-2015, 11:49 AM
Yeah that's easy to answer. Aluminum swing arm. ;)

hmm, I just saw that Derbi also put as aluminum swing arm on the Senda--without going to the linkage. I use to know the reason for using this offset. It has something to do with putting the braking force to the chassis so that the suspension can properly perform, but I really don't remember. Guess some research is in order. ;)


Looking at this photo I think I can see why they did it. With the upper support beam there's no room to have the brake get its support from the swing arm. Comparing it to the image below with the classic GPR.


10-24-2015, 04:30 PM
Mountain bikes used to do the linkage brake stuff to take out braking bumps under hard rear braking and roots, but they've gone away from it since anti squat and better shock tech has removed it anyways. Maybe the reason they did it I this bike. Might have a crazy suspension path that squats under braking without it

10-25-2015, 01:01 AM
The stock petcock on this bike failed within the first hundred miles or so. Since then I've been running one from a scooter. The sad thing about that is the fuel sender on this bike is part of the petcock. So I've never really had the luxury of a reserve, or a get gas you idiot light. Which means that I've always had to keep an eye on how much fuel was around. Since that's the case I might as well go for the good stuff.


The Malossi high volume petcock. From these photos you can see it's a huge difference from closed to open. It takes about six revolutions to open it up all the way! I'm planning on leaving the plastic side fills off the bike this time, so I'll be able to sneak my hand in there to shut off the fuel.



10-26-2015, 09:47 PM
I am so looking forward to running this engine.


10-27-2015, 12:39 AM
Thing looks like a beast! So are the stroke crank cylinders just taller so the ports are higher? Or what makes them striker compatible? Wouldn't a spacer work on pretty much any cylinder?

10-27-2015, 01:51 AM
Hey D,

Yeah that's a really good question, and I've kind of played around with it. When the Xtreme 45 seized I pulled out the MetraKit Prorace 43 that I have from a previous bike. I no longer have the 43 crank because I gave it to someone that I thought needed it. Anyway, I tried to employ the 43mm Prorace with the 45mm Airsal crank using some base gaskets to make up the extra space. I was able to make up the space, but the engine wasn't happy. Now as you can see from this photo there was a pretty bad air leak. So that didn't help it run, but I think the real reason is the port timing was all messed up.

The Airsal kit for the Derbi EBE075 ships with a spacer. The stroke on the 075 is 45mm too. I've even thought about putting the Xtreme 45 kit on an 075 engine. This should work, but it needs a spacer to work. But, it's possible that fitter with an Airsal crank that the 075 engine would work without a spacer. I think the difference is in the rod length, and placement on the crank between the Airsal crank, and the 075 crank. Since I have a couple of 075 engines, and there are no longer any kits available for them I will probably attempt something like this as a solution. I may also try a 40mm crank, but that's all future futzing about. ;)

Another thing, from the bottom of the transfer ports to the top of the cylinder is the stroke length. So if you just use a spacer to get the bottom of the transfers to the correct location the stroke will still be off. I knew that with trying the 43 stroke Prorace, but I figured it be worth a shot if I could get it to work. :lol:


10-28-2015, 12:11 AM
This is interesting. Barikit makes a 1.5mm spacer (http://www.twostroke.se/product.asp?product=12445&attrib=1&attrib1=2848).

To use Barikit's crank sustained stroke need these cylinderspacers to raise the cylinder so that the piston does not hit in the top cover!


10-28-2015, 11:47 AM
tora do you have any trashed cylinders left over

10-28-2015, 12:17 PM
I have a bunch. I've collected them from other folks so that I could to port maps. What are you interested in? Pretty much all that I have are for the Derbi engines. Someday I might get them re-plated--if I can find a place that will do it for a reasonable price.

10-29-2015, 10:44 PM
Progress has bene a little slow thanks to the attention I've recently been giving to the other bikes, but I'm still moving forward with this one. Made some progress with the faring mounts yesterday, and will probably make some nice progress with them tomorrow. This came back today toot. :)


10-30-2015, 10:16 AM
tora do you have any trashed cylinders left over
I have a trashed aluminum Malossi AM6 cylinder you can have. Not sure exactly what specs are but I'll snap some pics this weekend and send to you. It came with a used AM6 I bought for spares.

10-30-2015, 10:17 AM
Wow that Brembo front brake lever and master cylinder are sweet!

10-30-2015, 12:53 PM
Almost the best master you can put on a bike like this one. :) But there are some other cool things for this bike I've yet to post about. It's coming. ;)

11-02-2015, 07:40 PM
Figuring out the bracket strategy would be so much simpler if I could just TIG weld some posts onto the frame. ;)

Now that I have the first bracket in place it's a little easier to start with the following brackets. But to do so I first have to make sure things will line up well enough. I imagine at some point I'm going to have to deal with the pipe too. :eek:




Looks like the front side fills may even work with out modification.



11-04-2015, 10:29 PM
Some time ago I bought into the whole Lithium Iron Phosphate battery solution. Although maybe I should rephrase that as problem generator. I bought four of the Ballistic LiFePO batteries, and the fancy charger. The early batteries all had manufacturing issues. They didn't work right. It took me until today--years and years to get a solution. About a month ago one of the batteries was replaced with a working unit. One of the four that I had bought originally worked. That brought me up to two working batteries. Ballistic really didn't seem to stand behind their product, but the rep for my dealer worked it out so that the store got credit for the batteries. The store then ordered a couple of the Shorai's for me as replacements. I got those today. Huge thanks to the rep, and the store for making this happen.


So how do the two batteries compare? On the Ballistic side I have the EVO2 4 cell 100-010. It retails for $109, weighs .979 pounds, has 2.3Ahrs, and 120 CCA (cold cranking amps). There are two Shorai's for the Derbi. The LFX07L2-BS12, and the LFX09L2-BS12. the 7 is listed as the standard and the 9 as the "duration" model. I went for the 9 because I just didn't want issues. Specs for the 7 are $99 retail, weighs .93 pounds, has 102 CCA (they don't list Ahrs). The 9 retails for $115, weighs 1.28 pounds, and has 135 CCA.



The Ballistic is much smaller, and a little bit lighter than the 9. It looks much sexier thanks to being black and red, has nicer brass battery posts, and just gives off the impression that it is high tech. The Shorai is shaped like a standard battery. Has the same kind of lame battery posts as a standard battery, and just looks totally boring. It's not the sort of thing that people are going to look at and think wow that looks nice. And yeah those lame style battery posts that are a pain in the ass to use.


The Ballistic employs closed cell foam for placing it in the battery compartment on the bike. They provide an over sized piece that can be cut down to fit. Works quite well, and looks cool. Shorai provides multiple layers of foam padding that is taped to the battery. You keep adding layers until you get enough to keep the battery in place. You can guess which one I think rocks, and which one is a dumb total pain in the ass.



Both batteries employ a special control connector so that when you charge them it can direct the charge to an individual cell. This is a huge benefit because you can ensure that all four cells are charged to the same level. You can also find out if a cell is going bad.


This is the Ballistic charger setup to do a four cell balance.


This is the Ballistic getting a balance.


This is the Shorai getting a balance.


Conclusion at this point. I've not yet employed the Shorai. You can tell that I actually prefer the esthetics of the Ballistic. I think the Americans just did a better job with the looks, and packaging than the Japanese. This is why I probably stopped buying Japanese bikes. I appreciate things where the design doesn't look like it was developed to hit a price point. Sure the European bikes are designed that way too, but they don't look like it.

Whenever a new technology comes around there are growing pains. It takes a while to work out the issues. I can totally cut Ballistic some slack in that direction. Clearly they figured things out, and fixed the issues. But they did something so morally apprehensible that I just cannot recommend their product--yeah even though I honestly believe they have a better product (at least with regards to looks and design), but the way they treat their customers is total bullshit. Right away they should have admitted they had a manufacturing issue, and just replaced the batteries. But they didn't--they didn't do it for years. And they made it so difficult on the dealer, the rep, and on the customer. That's just wrong.

The Shorai doesn't look as nice with regards to design. But it does look like it is a quality product. They too have had a few years to work things out so I expect that these batteries will be problem free, and I hope I never have to find out about their customer service.

Wrapping it up. Yup the Shorai is what I would suggest you check out if you are in the market for one of these hi-tech units. Now does a $115 dollar battery really succeed as all that when a $20 Yaussa can do the same job with a bit more weight? Probably not really. Which makes you wonder why Ballistic didn't support a customer that could have spent $80 buying lead acid batteries actually spent $500 getting four LiFePO batteries, and charger.

11-04-2015, 10:57 PM
i am using a $4 battery on my 125 lol

11-05-2015, 08:06 AM
All this battery talk reminds me I have a homebrew LiFePO 4cell A123 cell battery somewhere in my parts stash. I should probably find it and recycle it before something nasty happens. I bought it in 2010 and didn't do anything with it as I converted my race bike to magneto ignition.

11-08-2015, 03:10 PM
I've just got some cheap lithium battery on my bike. 3.3ah, it's really small and weighs about 500 grams.

Surprisingly my charging system has managed to keep power in the battery, I'm guessing as they charge so fast.

11-08-2015, 06:22 PM
It's amazing the array of batteries that are available today. It probably has a lot to do with portable devices, and electric cars. I intend to install one of the Shorais in the Wicked GPR, and one in the Silver GPR. Currently in the Silver Bike I have the Yuasa that I bought to use in the Red Bike while the whole Ballistic thing got worked out. It took two deep charges on the battery charger to bring it back, as it had been sitting for about a year. But now the Yuasa is working pretty well. So I'm a little hesitant to swap it out. :eek:

I've been doing the balance charge on the three LiFePO batteries. There is a fourth one that goes with the Monza moped. I'm going to have to check into that one soon too. Each of the four cells pop up to about 4 volts. The Shorais are doing well, but in the Ballistic the levels don't always stay there. I think the Ballistics that I've got are going to just be a loss. I really do feel burned by them. :devil:

11-09-2015, 06:15 AM
I installed one of the Shorai batteries in my RS a few years ago and haven't had a single issue.
Haven't even needed to stick it on a charger.
I have yet to get around to buying one of those slick chargers like you have there, but thinking it might be worth the investment.
Looks way cool too.

I went all in and got the LFX14L2-BS12 for my RS.
14 Ah equivalent with 210 CCA at 1.46 lbs.

Our winters get down right Arctic feeling and I have always had issues with the little Lead Acid batteries crapping out.
Years and years ago I started buying AGM type batteries for my other bikes and was very pleased with their "over-wintering" endurance.
Only issue with them is that they still weighed as much as a standard battery.
When it came time to refit the RS, I did some homework and opted to buy Shorai over the Ballistic ... Glad I did !!!
Sucks Ballistic doesn't stand behind their product with any amount of pride.

I do agree with your take on the foam and aesthetics, however I must say that the Shorai dropped right in the RS's battery tray and no foam needed.

11-09-2015, 09:51 AM
Our winters get so damn cold that I sometimes think--well it's time to put on a hoodie! In fact it's so cold here that I can run straight water in my cooling system, and never worry about it crystallizing and breaking my engine. This one time, at GPR camp, it got so cold, that I had to wear a long sleeve T-Shirt! :lol:

Seriously though--I never have environmental issues with hot or cold here in the Bay area. Our temps are very mild. I have read that the LiFePO batteries don't do so well in the actual cold, and you probably wouldn't want to run them in a snowmobile.

The 14 is a big jump from the recommended 7, and here I thought I was doing extra by going with the 9! On the Silver Bike a strong battery will be nice since it still has the starter, but on the Red Bike, and the Wicked GPR it's not an issue since both bikes have had them removed. All the battery needs to be able to do with those two bikes is run the clocks, horn, and blinkers when the bike is at idle. About as low stress as you could ask of a battery, and yet the Ballistics weren't even up to that challenge. :eek:

Of all the Ballistic gear I've bought the charger seems to be the only thing that actually works. But it looks like it's just a rebranded item that they slapped a sticker on, and called it their own. It could probably be sourced from the original manufacturer for an even better price--and likely as not better customer service too. The Shorai charger doesn't look to have the same feature set--it's more plug and pray style. The one thing about the Ballistic BMS (battery management system) charger is that by today's standards the UI is horrible. It's like an early 1980's paged menu from hell. In the 80's that was fine. It's all we had, but here in 2015 you'd expect that thirty five years would have had an effect. Nope!

Since I have a bunch of the closed cell foam from the Ballistics I'm probably going to employ that with the Shorai. ;) You bought the 14 which is larger, significantly so, than the 7, or the 9 so I can see where that would drop right in. I wont have that with the 9. These batteries are tiny. The Ballistic even more so, but even still the Shorai 9 is still quite small. :)

11-09-2015, 02:57 PM
We have rain today in San Francisco. This is good as we are suffering one of the worst droughts in our recorded history. So I'm cool with it, but it does limit what sorts of things I can do with regards to bike wrenching. Thus I figured I might as well install the Shorai into the Wicked GPR!

The battery box.


The Shorai sitting in the box for sizing.


Trimming up the first piece--a hack saw cuts through this stuff like butter!



Fitted in with two buffer pieces of foam. I decided to offset it rather than center making it easier to get at the terminals.


They include two extra screws/nuts. This is a nice touch. The also put some of the foam on the nuts to make it easier for the screws to reach the nuts with these darn icky terminals. Yeah I know why they do it this way, I just don't like this style of terminals.


All installed, and happy. The blinkers, and horn tested quite nicely. ;)


11-09-2015, 05:23 PM
This task has been a real challenge for me because I just don't have the proper tools, or supplies to pull off what I want. :/

The basic plan is to set up a bracket that is similar to what track bikes employ. It's basically a rod coming from the bike, and a tube on the faring that slides over the rod. Then an R clip is employed to hold them together. Lots of race bikes use this method, and I think this is really the way I want to go for the Wicked GPR.

I have some of these parts from things I've collected, but I only have partial pieces. Probably because the rod section would be on the bike.


For the bracket I have some aluminum stock. I need about a 45° angle bent at 90° to get what I want. But I don't have a brake with which to bend the metal. Something like this would be great!


But this is what I was able to fashion up.


And of course I had to employ a persuader.





Here's the general idea:




Now I need to source some rod that will fit into this tube. It looks to be about 14mm ID. Then drill some holes, trim the pieces, tap the rod in order to attach it to the bracket with a fastener, and I'm close!


11-09-2015, 07:03 PM
I wish I lived in an area that had as mild of temperatures as that ...
I spend about 4 months in Under Armor thermals and at least a solid 8 in hoodies.

This one time, at GPR camp, it got so cold, that I had to wear a long sleeve T-Shirt! :lol:


I read about the battries not liking the extreme cold as well, and meant to bring it in the first winter ...
I did go out and fire it up from time to time (once a month if it was lucky) and never had an issue.
Dead of winter at night and temps nose-dive into the negatives, hell last winter we had a 3 month stretch that didn't brake out of the 20's.
So I'm not sure where the threshold on cold is for these batteries.

Those "quick release" fairing mounts are so nice when wrenching, nice touch.

For quick metal bending (thin stuff) I have a pair of these and they work amazing !!!


Mine are from Snap-On but Vise Grip and some others sell them as well.
Search "sheet metal pliers" ...

11-10-2015, 12:22 AM
Sometimes I'm really surprised at how many steps it takes to achieve what even remotely seems like progress. The local hardware store that usually has everything I need didn't have any aluminum, or plastic tubing or rods in the sizes I wanted. They did have wooden dowels which I almost went for, but decided to see what Home Depot might have available. At the HD I found some aluminum 1/2" tubing that fit inside the aluminum faring mounts. I'd rather have used the plastic mounts because they seem better, but okay whatever is going to work.

I picked up the tubing, some M10 bolts, a tap, and some washers.


I did some tests with threading the tubing. It was difficult, but eventually I was able to get it threaded.



I have a tubing cutter, but it didn't work so well. I ended up using the hack saw to cut the tubing. I needed two inner tubes that I'll be bolting onto the brackets, on which the outer tubes bolted to the fairings will slide. I may have to shorten the outer tubes a bit. The aluminum ones thanks to the nylon mount are a bit wider, and because I'm bolting on the inner tubes I need more room all around. It doesn't help that the bike is actually much wider that the bike for which the farings were made! If I had a TIG welder I probably wouldn't be messing around with all this stuff. I would just weld the inner tube to the bracket. :lol:



11-10-2015, 12:39 AM
Hey Xero,

Speaking of GPR Camp. I'd really like to have a rally for these kinds of bikes--similar to what the Moped cats do for their rallies. I wonder if there would be enough interest for something like that here in the States.

Four months off is better than I did this year. Thanks to all the bad drivers running over my bikes I really haven't been able to ride until I got the Silver bike on the road. I still haven't really gone on a proper ride yet this year, and last year was quite sparse too. Seriously for about two years all I've been riding were my BMX bikes--and thank goodness I had those to ride, or I probably would have gone insane. This moto drought is going to change though--gosh darn it! :lol: Even just riding out to the hardware store today was a treat. I just love the sound, smell, and feeling of these bikes. Just puts that big smile on my face. :D

I do hope these faring mounts are worth all the effort. I mean it's totally goofy the extent to which I am going to get what I want, but hey this is the Wicked GPR so I have to go for it, you know? ;)

Those sheet metal pliers looks so handy! :)

I think 20°F is below the suggested rating of the the LiFePO batteries. Nope I was wrong, it is right at the suggested low point (http://shoraipower.com/faq)!

A. Down to about 20 degrees Fahrenheit (-7C) most users find that they can start normally on first crank. If your headlight comes on at key-ON, it is good for the batteries to flow some current before cranking in cold weather. The suggested headlight-on time before cranking depends on the temperature. If starting at 40F/5C, 30 seconds will help wake the battery and increase cranking performance. If at 0F/-17C, leave the lights on for 4~5 minutes before cranking. The result will be a better first crank, and longer battery life. If the engine fails to start on first crank, that first crank has warmed the battery, and the second attempt will be much stronger. Other accessories that can be turned on before cranking can also be used for this purpose, such as heated gear, radio, etc... Insuring that the battery is fully charged after storage also improves first-start performance in cold weather.

11-10-2015, 01:05 AM
Hey Xero,

Speaking of GPR Camp. I'd really like to have a rally for these kinds of bikes--similar to what the Moped cats do for their rallies. I wonder if there would be enough interest for something like that here in the States.

So down to have an AM6/EB01 eurotrash rally!

11-10-2015, 03:20 AM
Been looking into the Shorai batteries over in the UK and found the following info that seems to add a bit more to TT's previous post (although I take no responsibility for its accuracy)!


Think I'm gonna have to look at the cost of shipping from the US!

11-10-2015, 04:56 AM
Damn that's like half again as much. Well considering the weight shipping will probably be quite reasonable! :lol:

11-10-2015, 10:28 AM
just get the wps featherweight batteries. I have one in my dr350 right now it rules.

http://www.ebay.com/itm/LITHIUM-Best-Price-Aprilia-RS-50-Li-ion-Battery-save-2kg-/281818666678?hash=item419db396b6:g:9pMAAOSw9r1WEnb e&vxp=mtr

http://www.ebay.com/itm/Featherweight-Lithium-Battery-Race-Track-WPS-Reduce-Weight-Light-490-2500-/121383745451?hash=item1c4308f7ab:g:1lQAAOxyQfJThm0 5&vxp=mtr

11-10-2015, 01:11 PM
Those batteries would basically give Mark what he's got already--something not quite up to the task. Which is why in his thread I suggested getting a LiFePO battery like Xero did, because he could get over 200cca, and still have it fit in the battery compartment of the RS4. ;)

I went all in and got the LFX14L2-BS12 for my RS.
14 Ah equivalent with 210 CCA at 1.46 lbs.

The Ballistics that I bought were for bikes that no longer have starters--so I didn't need a proper battery for them. I do think it's funny though that 100cca isn't up to the task of starting a 50cc bike, even if it's a modified one! :lol:

Mark if you have a battery charger, not a trickle, but a real one with a start mode, you could hook it up to your bike when it is warm, and do a test to see if you have ample power laying around will the bike start right up. ;)

11-10-2015, 03:34 PM
Those batteries would basically give Mark what he's got already--something not quite up to the task. Which is why in his thread I suggested getting a LiFePO battery like Xero did, because he could get over 200cca, and still have it fit in the battery compartment of the RS4. ;)

The Ballistics that I bought were for bikes that no longer have starters--so I didn't need a proper battery for them. I do think it's funny though that 100cca isn't up to the task of starting a 50cc bike, even if it's a modified one! :lol:

Mark if you have a battery charger, not a trickle, but a real one with a start mode, you could hook it up to your bike when it is warm, and do a test to see if you have ample power laying around will the bike start right up. ;)

I have just checked and I currently am running a Yuasa YTX5L-BS which I believe only has 4A and 80CCA!

For ease of wallet, I am considering trying the Enduroline YTX5L-BS variant which is a 5A 125CCA alternative.

11-10-2015, 08:29 PM

For ease of wallet, I am considering trying the Enduroline YTX5L-BS variant which is a 5A 125CCA alternative.

I suggest just sucking it up and spending the extra cash on a good battery.
Buy standard issue junk, get standard issue junk, buy more standard issue junk to replace standard issue junk,get more standard issue junk ...

lather, rinse, repeat


I'd really like to have a rally for these kinds of bikes--similar to what the Moped cats do for their rallies.

How "Billy-Bad-Ass" would that be !!!

It's a shame really, that the smoke crowd is so dispersed across the States these days.
I would be so up for a "GPR Camp" (LOL) but it's against my Religion to trailer a bike.
I would have no qualms with ripping the ZX across the Country, but I'm too old, lazy, and poor for a 2 Stroke Marathon like that.
Head East, way East and I'll do my best ...

Helpfull Hint of the Day :

Tapping straight is best done with the tap vertical, it's a lot easier to sight straight and square when the parts are upright.

11-11-2015, 02:23 AM
Hey Guys,

It would be so much fun to have a GPR Camp. ;) Maybe we should start up a thread in the off topic section to see what kind of traction the idea has on this foro, and see what support we could get. I use to get a bit hung up on trailering a bike, but doing track days kind of changed my feelings on this, because well you can't ride a proper track bike on the street. ;) That and dirt bikes are kind of the same thing too. I'll have to do a post of the bike carrier that I have on the Saab. JP helped me make a custom setup, and for these small bikes it works really well. :)

Mark, if you can try a test with a battery charger that can be set to start mode. I don't think 100ish cca is going to work for you. I'm running something close to that with the same sort of results--that is to say no improvement. I'll probably put the second Shorai in the Silver bike to see if a 9 with 132 cca makes a difference, but like what Xero did with over 200 just might be what it takes.

Xero, as you can see from the photos I don't have a shop within which to work. I either work in the kitchen, or out on the street. It totally bites, but it's all I have access to currently. I didn't have a way to get enough grip on the tube without putting it in the vice the way I did--and even then it still spun. This setup did result in bad threads in the first part of the tube, but getting the tap in far enough I could get decent threads cut once the tube forced the tap to straighten out. Totally non-optimal, but I pretty much have to work in such conditions all the time. Oh to have a proper shop within which to work! :eek:

11-11-2015, 02:35 AM
I did get a little bit more time in on the bracket action. I actually got one nearly functional! Here's the bracket attaching to the frame where the stock bracket mounts.




This is the inner tube mounted to the bracket.


And here is the system working. I still have to trim off the extra material, but you can see how the outer tube is slid over the inner tube. I do plan on adding a hole for the R clip, although there's plenty of friction holding it in for now.




11-12-2015, 01:51 AM
I'm at the point where it's starting to show what it will be like when it's finished. It's all very exciting. However, I keep getting drawn away by other events, so it's being extended. Little progress here, little progress there...


The side fills look like they will work out great, even following the curve of the frame. This is one of those happy coincidences. :)



There are somethings that appear to be intersecting--unfortunately. The lower skirts will have to be trimmed at the side stand, and behind the rear brake where it looks like it will come in contact with the swing arm. Also it seems to be centering a bit on the throttle side of the bike. This could be related to the plastics contacting the side stand mount.





11-14-2015, 05:46 PM
Get the left side together today. Progress has slowed down a bit because of the other things going on. The interesting thing is how stable the plastics are even without all the brackets in place. And while I still have a ways to go it is so since to see it all coming together.


11-19-2015, 02:26 AM
I saw this article today about cylinder plating (http://www.mt-llc.com/pdf/98winter_snowtech_article.pdf). It's a worthwhile read, and goes a long way towards explaining why you want to be running a plated cylinder rather than cast iron. ;)


11-19-2015, 10:49 AM
you can now plate cast iron

11-19-2015, 11:10 PM
Started placing the engine in the cradle. Need to do this in order to see how the pipe is going to interact with the plastics. The front engine mount is a bit tight. This is due to the tolerances getting a bit tight when the crack was repaired.


The rear mount on the GPR is nicer than on an old style RS because it isn't through the swing arm bolt. There is a coupler that sits between the swing arm mounts. You do need to loosen the swing arm bolt, 22mm skinny socket required, to rotate the coupler. Notice how the swing arm has a notch for the coupler to rotate into position. These Derbis are classy bikes--and people wonder why I prefer the Derbi to the Aprilia. :lol:


Soon! By the way it is a lot easier to insert the engine without the spark plug installed. ;)


11-20-2015, 12:31 AM
the engine doesn't mount through the swingarm on the 2000 ish rs50 either

11-20-2015, 02:33 AM
Got some more things done. The engine is now sitting in place with the bolts. I mounted the pipe, and it looks like there are some issues with it, and the plastics.








11-20-2015, 04:24 PM
the engine doesn't mount through the swingarm on the 2000 ish rs50 either

Seems I misunderstood something you guys were talking about in your conversion threads. Where the transplanted engine employs a rear engine mount where you used the swing arm bolt. The Derbi engine employs an M12 rear bolt, and the AM6 only uses an M8 for the rear mount. So yeah I didn't get that correct (thanks for the update!), but I'd still prefer the Derbi method because an M12 is way more secure than an M8. ;)

On the Senda bikes Derbi does use the swing arm bolt for the rear engine mount--just like the motocross bikes, and probably the same as the bikes from which you source your engines for the swap. Interestingly if you wanted to do a conversion on the GPR you wouldn't have to mod the swing arm, because you could just remove the coupler, and then set the engine.

11-20-2015, 11:06 PM
Putting 2004 plastics on the 2005 is quite a challenge. So many interesting challenges keep showing up. Like the pipe and the plastics. It looks like a bit of twisting and turning and the pipe will fit in most of the plastics will clear. Although it's a bit close in some places.



The stock pipe mount was getting in the way of placing the pipe in a location that would work. With a bit of reangulation via a crescent wrench.


Then things started clearing.







I'm probably going to have to come up with some sort of mounting bracket.


Oh the Jolly Moto. :)



11-21-2015, 12:39 AM
Seems I misunderstood something you guys were talking about in your conversion threads. Where the transplanted engine employs a rear engine mount where you used the swing arm bolt. The Derbi engine employs an M12 rear bolt, and the AM6 only uses an M8 for the rear mount. So yeah I didn't get that correct (thanks for the update!), but I'd still prefer the Derbi method because an M12 is way more secure than an M8. ;)

On the Senda bikes Derbi does use the swing arm bolt for the rear engine mount--just like the motocross bikes, and probably the same as the bikes from which you source your engines for the swap. Interestingly if you wanted to do a conversion on the GPR you wouldn't have to mod the swing arm, because you could just remove the coupler, and then set the engine.

Yeah I agree that the derbi swingarm is a much nicer unit than the 99-05 RS50 unit, that is for sure. However you may still have to modify the swingarm if doing an engine swap, depending on the width of the donor engine. If it is wider than the derbi aluminium swingarm, you will have to machine it to end up being wider. If there aren't supporting cups, you may need to weld supports on it, and then since it is aluminium, you'll need to get it heat treated once again. It could end up being a much bigger pain in the ass because it's aluminium vs steel. Hard to say though. If doing an engine swap, it could be easier to machine the cases of the new engine to fit inside the derbi swingarm with the correct sprocket offset. Either way it will just take some nice measurements.

With the steel swingarm, you don't need to worry about heat treat, at least when dealing with the thickness of the swingarm, however you will have to weld in an additional brace to make up for the center being cut out of it.

In terms of fastener design, I don't think the M8 as an issue for the rear mount. When designing and building the formula sae race cars, we would use #10-32's everywhere! for suspension arms, brakes, axles, swaybars, you name it. Lots of force calculations with fatigue analysis, etc. We originally had like 5/16" bolts on everywhere and they ended up being absolutely overkill. Going to smaller fasteners was a major weight reduction. In my humble view the M12 offers no real improvement to an M8 when considering the weight increase. The available tension that the m8 fastener can pull in similar conditions is more than enough. However if you were to have a derbi power plant that was making say, 90 horsepower instead of 35, then perhaps an M12 may be alright, but keep in mind that my CR125 used m8 bolts from the factory for every location other than the swingarm pivot.. haha.

11-22-2015, 03:57 AM
Not exactly sure about placement yet, because I still have to trim the plastics, but I have a pretty good idea about what will be going on. :)


On another note, does anyone know what the couple sitting back to back represent? All the other stock images on the Derbi panels I get, but that one eludes me.

12-07-2015, 03:22 AM
Back on the first page of this thread I posted about sensors (http://www.apriliaforum.com/forums/showthread.php?312028-Derbi-Reactivation-Project-The-Return-of-the-Wicked-GPR&p=3930094&viewfull=1#post3930094). This bike has a bit of a ways to go so I keep doing the research with regards to sensors. I've come across some interesting things. The MA cats discovered a really inexpensive way of doing EGT, which I think is an amazing DIY project. I've also found out about two more interesting Kart gadgets. The first, and probably most attractive is the Starline Corsare, but there is also the Alfonse setup. Lets see if I can properly cover these in a post, or three. ;)

I'll start off with the inexpensive setup. The whole setup is pretty much laid out in this Instructables (http://www.instructables.com/id/Simple-CHTEGT-Readout-for-Paramotor/). The dude even made a PDF of the setup (http://www.instructables.com/id/Simple-CHTEGT-Readout-for-Paramotor/?download=pdf). (You can also read about this in this MA thread (http://www.mopedarmy.com/forums/read.php?1,3919612).) The one rather glaring disadvantage with this system is the sample rate. It's something along the order of 4 time per second. This might not be enough to catch a really quick malfunction, but should be good enough to help you zero in on a really good tune.

He found a digital temperature gauge, and a K type thermal sensor. Taking a couple of these gauges, and getting creative with the sensors you can gave both EGT, and Head temp. Now he does it with a spark plug for head temp, but you could just as easily employ the sensor with a water temp sensor. These things can be found on eBay for less than around $25 for both gauges, and sensors. You'll probably want to make up a project box with in which to house them.

http://cdn.instructables.com/FNA/L11J/IFPMMEZ3/FNAL11JIFPMMEZ3.MEDIUM.jpg http://cdn.instructables.com/FGM/HYEE/IGP0ILRP/FGMHYEEIGP0ILRP.SMALL.jpg

Here is his parts list

1 - CHT K type Thermocouple Temperature Sensors for Cylinder Head Temperature (14mm)
1 - Maplins project box
1 - Maplin Rectangular illuminated rocker switch N84JZ
1 - Thermocouple Red Digital LED 0-999C Temperature Thermometer Panel Meter Display
1 - Thermocouple Blue Digital LED 0-999C Temperature Thermometer Panel Meter Display.



12-07-2015, 04:29 AM
The Starlane Corsaro K (http://www.starlane.com/vedit/15/cronometro-gps-indicatore-marce-contagiri-cambio-elettronico-acquisizione-dati-PRODOTTI.asp?idprod=1146) is another kart dash module. This one has some extremely cool features. The dash and the connectors to the sensors are housed in two separate physical units that communicate via Bluetooth. The dash will also communicate to your computer via Bluetooth to upload data. The remote even has a mini solar panel on it so you don't have to charge the battery. The main control of the dash is via its touch screen.

The next innovative feature is the ability to take your track routes and overlay them on to satellite maps. Why is this cool? Because by combining them you can see which paths through the section of the tracks are faster. What? That is so cool, but they didn't stop there. You can upload your lap, and compare it with other people's laps. So you buddy could post his hot lap to teach you how to improve. You can also take video of your ride, and then overlay captured data into the video.

And yeah there's all the other bits you'd like to have in such a system like EGT, and CHT sort of stuff. Plus GPS, RPM, oh and least I forget--it will infer your transmission gear based on speed and RPM. Yeah this is one cool box that is setting a pretty high water mark for its competitors.

Near as I can tell the software only runs on MSW, which is sad, but you can probably run it in a virtualizer if you don't have a crapy OS machine. :lol: It can be DLed from here (http://www.starlane.com/vedit/15/download_form.asp?pagina=1755).

Why the K? The K is for the kart version, which has two temp sensors, and RPM. The other ones have more features, but the price goes up. You can expect to pay just under $500 for this dash setup. From what I've read that would include one sensor. But you can get a K type sensor from lots of places. :)


Here's a video in German explaining, well something. :P


Here it is installed on a bike to give you some idea of scale.


Here's an overlay video.


Map overlay action.


There are some different screen layouts, and even a fancy color screen version in the Pro model.



12-07-2015, 01:11 PM
That EGT is super awesome. I am not sure how much I dig only C but I can work with that! Do you think that sensor can deal with the 1000F temps though?

12-07-2015, 02:15 PM
It's rated to 800°C, which seems to be good enough. You can learn to employ Celsius--it's actually easier, and it's much better to get your head thinking in metric units anyway, because science. Considering all the time you spend in Europe you can probably already do it. :)

12-07-2015, 09:40 PM
Alfano makes a number of units for these applications. The Pro3 goes for about $300, but that looks to be without sensors. Still it would provide RPM, and two temps sensors, one of which would be a K type which could be used for EGT. So if you were to do your own wiring it might be viable. Otherwise if you buy their sensors it jumps up well over $500. Ouch! The Alfano ADM4 is a step up, and more like the Corsaro with the sensor box separated to a Bluetooth input box. Interestingly the ADM4 isn't all that much more than a Pro3. Looks like it goes for about $330, and again all sensors look to be extra.

There also seems to be a few software packages available to over lay data onto video. One package is called RaceRender, another one is called DashWare. I haven't done more than notice that these were available.

A1020 PRO III EVO (http://www.fastech-racing.com/alfano-pro-iii-evo-gauge.html)

Our most reliable system yet! The PRO III EVO is the outcome of tireless testing and valuable customer feedback.

This system can stand alone with basic functions such as the taking of lap time, RPM, 2 temperatures (K and NTC type), and speed with a sensor. It can also be upgraded by connecting our GPS4 Module (sold separately). *See Options / Capabilities below, next to specifications.

Package includes:
1- PRO III EVO Alfano system
1- Magnetic Lap Time Sensor OR Infrared Receiver
1- RPM Sensor
2- AA Batteries

http://www.fastech-racing.com/images/thumbs/eadbda4a6d9c6d6714c0f8980740cd9e.png http://www.fastech-racing.com/images/thumbs/693c1a9a6eb6d507122ed952fcace331.png



Alfano ADM4 (http://shop.conceptracegear.com.au/product/4312/58053/alfano-adm4-abx4-data-logger/)

This latest kart lap timing system from Alfano uses Bluetooth technology which means there are no wires needed to connect to the display unit itself. Instead a separate box with 4 inputs is remotely mounted on the kart to which the sensors are connected. The data is then sent to the display via Bluetooth.
Lap timing is via a magnetic sensor which uses the magnetic strips embedded in the race track. The inbuilt memory records up to 100 laps which can be reviewed on the display after each session.
9 LEDs across the top of the unit display RPM limits or Lambda (separate sensor and box required) and two additional LEDs at the side of the unit alert to high temperature or pressure (separate sensor and box required).

Alfano ADM4 Features:

Lap timing to 1/100th second
Data recording 5 / 10 / 20 Hertz
9 LEDs – RPM / Lambda
2 LEDs – Temperature / Pressure
5 Engine time counters
Bluetooth connectivity
Water resistant to IP56
Dimensions: 133.5 x 90 x 28 mm
Screen: 77 x 45 mm / 160 x 94 pixels
Weight: 253 grams
Alfano Input Box ABX4 Features:

1 x Display input (BUS)
1 x Magnetic / Infrared timing input
1 x RPM input (max 30,000 rpm)
1 x Temperature input (max 1000 deg C)
Water resistant to IP56
Dimensions: 85 x 88 x 54 mm
Weight: 185 grams
Powered by 2 x AA batteries (included)



Software overlays




12-18-2015, 03:32 AM
Have you ever been hit by a cager? I have multiple times. Every time they claim that they didn't seem me. Now this wasn't me riding like some crazy person. Each time I was just riding down the street, and they ran into me (plenty of times I've successfully avoided getting hit too). The common denominator was they claimed to not see me. Other riders that I've spoken with have stated that of all the things they've tried from hi-viz vests, to loud pipes the only thing that has made any real difference was head light modulators. Federal law does permit these (https://en.wikipedia.org/wiki/Motorcycle_headlamp_modulator)--within some rather strict conditions. These things tend to go for about $60, and we'd have to mod them to work on our goofy bikes. But could one build one? hmmm. So I did a little searching.

I found this page with a pretty nice design (http://www.buchanan1.net/modulator.html). The two issues with this design is the need to have a photo cell switch to turn the device off at night, and that it modulate at 4 times per second (240 per minute). I probably have enough knowledge to add the switch, but I'm going to have to do some learning to figure out the timing. Looks like fun. ;P


This video illustrates how well they work. Skip to one minute mark to see the head light action.


Now there is some risk to riding with a modulated head light (http://www.zenreich.com/ZenWeb/motorcycle/headlightmodulator.htm). Lots of cops are unaware of the law. This shouldn't be a surprise to anyone that's been around the block. There are just too many laws for a cop to know them all. So it would probably be a good idea to have the federal law printed out (http://www.webbikeworld.com/Motorcycle-technical-articles/Modulator-regs.htm), and stashed on the bike in case you get pulled over. And remember a cop can legally fuck with you if they are ignorant of the law (http://thinkprogress.org/justice/2014/12/15/3603686/supreme-court-if-youre-a-cop-mistakes-about-the-law-wont-stop-your-drug-bust/).

12-18-2015, 08:29 PM
Stopped by Treats to say hello. They had just gotten in these new fuel filters (http://www.treatland.tv/aluminum-serviceable-fuel-filter-in-many-colours-p/metal-fuel-filter-many-colours.htm). Super cool, come in lots of colors, and they are rebuildable too. The neat thing is the flow hole on the red one is actually larger than the one on the OMG filter I had previously picked up for this bike. Also, it's more red bling for the bike. :)



12-22-2015, 01:24 AM
I should probably wait a while to post this--like once I have it actually mounted on the bike, but ah, well...

There's a bit of a story that goes with this little treat. My friend Greg got me checking out the Tyga website. I noticed that they make some parts for an Aprilia, but the model number didn't actually exist (RSV125 (http://tyga-performance.com/site/index.php?cPath=72_1035_1166_1167&osCsid=159fe7c8cf0e655bf0d50d50bd8458d6)). With a bit more investigation I figure out what they really meant was an RS4. I packed that knowledge away for a time when it would become relevant.

Later on the KTM 390 list one of the guys, Matt of Formula 390 (http://formula390.com), announced that he was becoming the US distributer of Tyga KTM 390 parts. I inquired if he would be abel to get other items. He said he would check into it for me, but that it wouldn't happen until he made another big order, and that would probably take a long time. That long time was incredible short!

While I really wasn't prepared Matt made it easy enough that I could actually get the part that I had figured would work on the Wicked GPR. This was a short time ago, and today it showed up. :)

I apologize for the bad photos. Eventually I'll get some with proper lighting. :P The unit itself is absolutely gorgeous. Tyga's fiber guy is amazing.









01-10-2016, 02:46 AM
Been cleaning house so I thought I'd stick the GPR up on the coffee table for a minute. :lol:


01-25-2016, 10:35 PM
Today I have something really special to share. I've had these since July, but was hoping to get them installed on the bike. I've been holding off on the installation until I get the fairings worked out. I'm actually surprised how long I've been able to keep these a secret. :eek: But it's time to let this cat out of the bag. I use to think these were unobtainium. Then Benji was able to get them for me. So if you too would like a set ask Benji over at Treats (https://www.treatland.tv)--Thanks Benji. :)



01-26-2016, 03:04 PM
adjustable in compression, rebound, and preload? nice. wicked upgrade.

01-26-2016, 04:46 PM
Scotty told me about these years ago, but they were big money back then, and there was no way I was going to get them. Benji found them on a closeout for a lot less, a whole lot less. :P

I'm hoping that the stock spring will work for my weight. Only one leg has a spring, the other leg is the damper. Kind of strange, but I suppose it reduces the weight somehow.

01-28-2016, 12:13 AM
Found this on a Japanese site (https://translate.googleusercontent.com/translate_c?act=url&depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ja&tl=en&u=http://kaneban.ocnk.net/product/926&usg=ALkJrhithr5rCp2F2Q71zGZBorV6hDD_vg). Probably wont be getting one of these, but for you cats with the newer front end Derbi/Aprilia replicas check out this triple tree top piece. These are about $450 with the current exchange rate.

http://kaneban.ocnk.net/data/kaneban/_/70726f647563742f32303133303231345f6163343265632e6a 7067003330300000660066.jpg http://kaneban.ocnk.net/data/kaneban/product/20130214_368b0b.jpg http://kaneban.ocnk.net/data/kaneban/product/20130214_06539e.jpg http://kaneban.ocnk.net/data/kaneban/product/20130214_670190.jpg http://kaneban.ocnk.net/data/kaneban/product/20130214_d067e6.jpg

01-28-2016, 02:16 AM
A couple of things have happened that have influenced me to change my plans a bit. I haven't been successful in getting the 04 farings to fit on the 05. The 05 is a bit larger. Aprilia was able to take the RS125 farings and put them right on the bike. Those farings do look a little bit too large once you know that's what they did for the GPR-RS. Also, now that I need to source some parts for the Silver Bike I might as well use these parts on the Silver Bike, and order up the fiberglass bits for the Black Bike. :lol:

I'm also going to put the Jolly Moto on the Silver bike (for now). I have two other exhausts to run on it but I can't find the manifold for either one. I contacted Arrow for a replacement, but they no longer have them. I need to see if Metrakit makes one available for the Prorace pipe. I've also got to look into getting a proper sized pipe for this Airsal Xtreme kit.

Hopefully tomorrow I'll make it over to Speedy's, and get the nice new front rubber put on the bike. As a place holder I put the 04 wheel on the bike. :)



01-28-2016, 03:35 PM
Rumenicestak posted a video of the Sava MC50 M Racer Super Soft tires. I have the front one that I got from Benji. Hopefully today I'll get that mounted. Still waiting for the rears to make it to the States.


01-29-2016, 08:25 AM
I have those on my 125 and my dad has the Sava full slicks on his, they both seem to grip really well

01-29-2016, 02:00 PM
Hey Matt, if I remember correctly you have the regular MC50s on your bike. Sava only recently came out with the SuperSoft version, and I'm still waiting for the rear super soft to show up at Treats--it's not even in their store yet. I have the front, and it's sticky. Made from the same compound (at least that's my understanding) as the Sava slicks. I put the Sava slicks on the track bike, and the are confidence inspiring! I'm sure your dad is totally enjoying them, right?

The thing about the MC50s though is that if you run them on the older bikes you wont get the proper profile. Those bikes should have a 90 80 17 up front, and a 110 80 17 in the rear. If you upgrade your wheels to the 2005 for the GPR, and 2006 for the RS50 then the MC50s will fit properly because those wheels are set up for 100 80 17, and 130 70 17. For the older wheels the MC18s are the tires to run. I've got these on the Silver Bike and they are very nice too.

You can run larger tires, but there's a cost--due to the different profile. If you look at the photos of the Black bike I've gone too large with those tires. I did this because I wanted a really good tire on the bike (and I was planing to run the 125 2T rear wheel which is wider). Bridgestone makes their GP-street tire in a 110 70 17 in the front, and a 140 70 17 in the back. The back is a multi compound tire! But because these tires were too big for the newer wheels the profile was wrong. The wrong profile will effect the handling. In our cases you get a rounder or more U shape rather then the the more V shape that you'd get from the proper size. This makes the bikes turn slower. Which is fine if you like riding the Super Slab, but I prefer the twisties. ;)

The big issue for this though is that when you are in a corner with the U shape you have a smaller contact patch than you do with a more V shape tire. Contrary to the belief that a wider tire will give you a larger contact patch it actually (on the wrong wheel) will give you a smaller contact patch in the corners (where it's important). So unless you are drag racing getting the proper size tire will allow you to go faster in the corners.

Here's an illustration


01-29-2016, 02:17 PM
incorrect, mine have the green label on them that says racing super soft right on them. I went to buy more from Benji but he was only getting the regular street compound in then so I switched to slicks, but I do in fact have race compound mc50's

01-29-2016, 04:21 PM
Where did you get them? As far as I've heard from Benji he's never had the soft rears.

01-29-2016, 05:55 PM
I bought them from Benji. in 2012

01-30-2016, 01:16 AM
I had a chat with Benji today. It turns out that they did have the soft tires back then! But a former employee mis-labled the tires, and so you got the nicer tires for a much better price. :P

01-30-2016, 01:27 AM
Sometimes you just have to take a photo.


02-05-2016, 04:27 AM
I know it's a blurry photo, but somehow I still really like this one--kind of feels like an oil painting. ;)


02-16-2016, 02:24 AM
I found a very informative page on air leaks over on Klemm Vintage (https://dakiniland.files.wordpress.com/2014/07/bury-your-head-in-the-sand.jpg). But as we all know on the web things (especially when good) have a tendency to disappear. So here's the text. Check out Klemm's page for the photos. ;)

Klemm has other good pages worth reading too, so check out their site (http://www.klemmvintage.com).

ABOUT AIR LEAKS - The engine you save could be your own

It happens almost every working day. The poor guy on the other end of the phone is giving me every intimate detail about his modified engine in hopes that I'll be able to rattle out the exact cause of his most recent piston seizure. After he finishes his detailed description I always ask, "When was the last time you pressure checked the engine?" The caller usually tells me, "Oh it's always had about 170 psi compression." I explain that a compression test and a pressure (or leakdown) test are not at all the same thing. What he needs is an understanding of what air leaks are and how to check for them.

The Theory of Air-leaks

Unlike all 4 cycle engines, the two cycle engines in all two-stroke engines must have a completely air tight lower end.

The normal vacuum in the 2 cycle engine's lower end will draw a mixture of fuel and air from the carburetor though the intake manifold. Once this fuel air mixture has been sealed off by the reed valve or a piston skirt, the resulting crankcase pressure moves the mixture through the transfer ports upward into the cylinder. A small "air leak" at a crank seal or an intake gasket will cause the usually perfect fuel/air mixture in the crankcase to become slightly lean...sometimes very lean. This lean mixture can quickly result in a seized piston. Air leaks are, by far, the number one cause of vintage engine piston seizures.

The Pressure Test

The step by step is :

A) Seal off the intake manifold with a plug or rubber gasket

B) Seal off the exhaust port with an automotive expanding rubber “freeze plug”.

C) Attach an air fitting that lets you pressurize the motor (usually thru the inlet plug or the spark plug hole

D) Pressurize the motor to 6-9 psi via a hose that has an in-line gauge.

E) Watch your in-line gauge for 5-10 minutes to confirm you have “absolutely no loss” of air pressure. A loss of even 2-3 psi is not acceptable.

F) If your gauge shows a leak, spray the gasket seams and seals on the pressurized motor with WD-40. The WD40 will make visible bubbles, and a leaking sound, when you spray the leak point.

The Technical Realities of Air-leaks

If you were to pressure test every vintage engine at your local weekend ride spot, you would find about 40% of them to have minor air leaks. Another ten percent will have major air leaks. Despite these potentially fatal leaks, most of these "leakers" will run for some time before they seize or score a piston. These same air leaks that would be almost instantly fatal to a pro racing engine, are easily tolerated by a low rpm recreational engine...why? The answer is related to H.P. per cc and engine loads.

A more modern 125cc motocrosser being run at full throttle makes as much horsepower as most vintage 400s. That means the 125 is making about 250% more horsepower per cubic centimeter than the vintage 400 engine. Since the 125 is constantly being operated at close to maximum output and peak rpms, the tolerance for an air-leak of any kind is “zero”. A high-revving 2-stroke engine with a significant air leak, is an engine that will soon produce a seized piston.

High output engines that have significant air leaks will usually run fine so long as the rpms are kept low. This accounts for why many freshly assembled engines operate well during the break in period, but seize the first time the throttle is hung wide open. Piston seizures related to air leaks are not just a result of an engine being run with an air-leak, but rather a result of the engine being run at close to maximum output with an air- leak.

Where to Look for an Airleak

When your engine seizes a piston...do not disassemble it. If your want to cure your seizure problem once and for all, pressure testing should be the very first order of business. The most common and most deadly air leaks take place at the crank seals, and at the inlet manifold/base gaskets. The ignition-side crank seal, in particular, is not only subjected to the fuels and pressures of the crankcase, but also the intense heat of the ignition compartment. It's very rare for an ignition-side crank seal to provide airtight sealing for more than two seasons of regular riding. Since most ignition covers are airtight themselves, an ignition-side crank seal leak can go on unnoticed for a long time on a stock output engine. If you find an oil residue in the ignition compartment when removing your ignition cover, there's a very good chance that your front seal is bad. Under any circumstance, it's good idea to remove the ignition cover and clutch cover when pressure testing an engine.

Intake gaskets, particularly ones with no sealer on them, are always candidates for small air leaks. Since all the fuel/air mixture passes by these gaskets, any leak at all can cause a serious lean condition. If the leak is on the bottom side of the inlet gasket, it will often be necessary to remove the engine from the frame to see and accurately locate the leak.

Very often, an older engine will have a small air-leak from a place you would never suspect. Leaks like this may only cause a loss of only 3-4 psi in 10-minutes …. But a leak like this can still deliver seized pistons just as easily as the bigger more visible leaks. Examples of these “odd leaks” are A) casting-porosities, B) up bolt holes to the heads of bolts, and C) into the transmission. Air leaks into the transmission are much more common than one would think, and so pressure testing the transmission is also a good idea …. That’s right, the transmission. This transmission pressure test is absolutely mandatory on any rotary valve engine, because leaks around the inlet joint will often not show up in a “standard” engine pressure test. The transmission should only be pressurized to 3-4 psi …. But it “must be air-tight to that pressure.

Air leak fables

Air leaks can cause lower end bearing failures…..wrong!

Inside a two cycle engine there are two different lubrication needs. The top end desires a deluge of a light viscosity oil while the lower end desires a slow trickle of a heavier oil. When there is a serious lean condition in the engine, a piston seizure will occur long before any lower end bearings begin to suffer. As most victims of air leak seizures have noted during disassembly, there is usually plenty of oil still present in the lower end. Lower-End bearings usually fail from the loads and temperatures of long term and/or high-rpm operation.

Setting the carb slightly richer to accommodate the air leak can avoid a failure...wrong!

Most air leaks draw a very minute amount of air at low engine speeds. In fact it's very common for air leaking engines to start and idle very nicely. However when the engine is brought up to full temperature at higher rpms, the castings will begin to expand and deflect slightly in different directions. At these higher temperatures the air intake of an air-leak can become many times greater. With this huge amount of additional air, even an "over-rich" air leaking engine will experience a critical lean condition after only a few moments of full load operation. This accounts for engines that run trouble free for years at moderate speeds with a low skill level rider, yet seize in the first few minutes of being run wide open by an expert rider. No amount of richness can effectively avoid the failure.

Air leaks can be accurately diagnosed without pressure testing…..wrong!

Uneven or wavering idling is a common symptom of small air leaks on motorcycle engines. However in the case of vintage engines, only huge air leaks will result in rising and falling idle speeds. The majority of the smaller, yet equally destructive, air leaks will have no effect on idling. Another common practice of finding air leaks is the spraying of contact cleaner at potential leak areas while the engine is running. If the spray enters an air leak area, the idle speed will increase noticeably. This method is useful for large leaks in accessible places, however the majority of smaller hidden leaks can pass this test.... In short...it's a total waste of time.

Freshly rebuilt engines are free of air leaks…...wrong!

Even engines that are rebuilt by the best technicians can air leak. About 20% of all freshly rebuilt engines will have small hidden air leaks. That's why most professional engine builders pressure test every engine before and after rebuilding. Installing fresh seals and gaskets is by no means a guarantee against air leaks.

Making the test gauge

The construction of a pressure test gauge is pretty simple (See photos below) . The photo shows a 0 -15 psi gauge, a standard air stem fitting, and a 1/4" hose barb all mounted in a brass "T" fitting. A hose from the barb fitting will connect to the fitting on the motor. A wide range of automotive freeze plug diameters are available at all auto parts stores, and the round inlet plug is easy to fabricate. For those that don’t want to hassle making a gauge, Klemm Vintage offers the gauge assembly for $39.

02-22-2016, 02:37 PM
When Paz and I built up the Stroked Airsal Xtreme we did the MetraKit clutch primary drive roller bearing upgrade too (MetraKit MRD 845D1610 TR/D 116). This is a nice upgrade for the Derbi engine because the stock system employs a bushing. Here's the photo essay of the procedure.






04-13-2016, 03:59 PM
So it would appear that this project has been languishing. That's partially true. But a bunch of action is about to occur. ;)

04-15-2016, 05:59 PM
A couple of teaser photos. ;)



04-15-2016, 09:04 PM
I have been wondering how I ever got along without an EGT gauge -
I have the Stage6 as above, and it's giving me a lot of insight into how seemingly small changes effect how our bikes run.
To prove this to my self, I made a seemingly small change (raised my needle one notch).
Aside from the obvious (four stroking anywhere in the throttle range except WFO) but the increased fuel charge kept EGT down ~ 50degrees over the entire throttle range (as opposed to the needle being in it's original position)
Over all, I've ridden about 100 miles using the EGT gauge, and haven't seen temps over 800 degrees F. One of the cool features of the Stage 6 is it has a 'max temp recall' function, so it's kind of irrefutable.

04-15-2016, 09:38 PM
Yeah I think our level is certainly increasing around here. I bought both so that I can experiment a little. Most folks wont drop the $100-$150 on the Stage6, or the $500 on the data loggers that feature EGT, but they might drop $10 plus a bit of effort for one of the Chinese units. Although I think that attitude might change when people see other people using these devices.

Are you also running a HTG on your bike? I've got an adaptor gadget and will be running something off of the head from the water sensor. I was using the TrailTech TT spark plug HTG, but those sensors have a really bad habit of failing, and who wants to be dependent on such an unreliable product? I still need to study up on how to read the two of them together, but it is suppose to really help with the tuning.

How far from the piston skirt did you mount the sensor on your bike? 15cm?

04-17-2016, 02:34 PM
you want to hit 1150F at top speed in 6th gear, tached the fuck out

04-17-2016, 03:53 PM
The more I run wth the EGT, the more I become convinced that I need the data logger functionality as well, to be able to compare all things logged... RPM, gear position, speed, cht, egt and be able to compare over my 'standard' buzz run route in my 'hood.

"Tached the fuck out" LOL

Back in racing days we always said "go into turn 1 WFO and let gravity sort it out..."

There is ome further discussion of thermocouple location here:

My take on it is you want it close enough to give you an accurate reading of what is happening inside the cylinder, but not so close you burn up thermocouples.
And it seems that everyone's installation will be a bit different, and you have to keep an eye on it, and understand that what my install says / does will differ from everyone else's.

Maybe you can create a little 'cottage industry' making those things with the Chinese bits, Tora ?
Need an investor ?


04-17-2016, 07:56 PM
frits overmars says if it is too close to the piston the fresh charge going out the exhaust (the scavenging part, before being pushed back in by the expansion chamber) will cool down the thermocouple probe that way, and you'll see cooler values vs what you'd see at ~ 150mm.. it makes sense to me

04-18-2016, 03:48 AM
Banzai also says 150mm. Those are two folks that I really respect so when I do get these things installed on the pipes it will be at 150mm. ;)

The Chinese units only sample at 4 times per second, which is too slow. But it's still better than nothing at all. So for folks that can't afford a Stage6 they should at least run one of the Chinese units--which are only $10. Now you have to make a little enclosed for it (could be a typical project box), and you have to extend the leeds a bit too. But still it's way better than just a CHT.

04-18-2016, 06:23 AM
4hz is fine. thermocouples are slow to react anyway

04-28-2016, 10:42 AM
Did you ever want to set your bike up with MotoGP switch gear? I did some investigating on switches some time ago, and I've been meaning to do a little write up on the switches, but I've been rather busy with things like GPR Camp and such. I really need to clear out the browser windows so I'm forcing myself to get this posted. ;P

I found some really cool switch gear, and some wantabe stuff too. Some of it is big bucks, and other come e-packed to your door for practically nothing! Apologies for the eBay links. I know they dry up over time, but for some of these things that's all that was available. The Evotech should be sourceable outside of eBay though. ;)

First up is the TKRP TC handle bar switch (http://www.tenkateracingproducts.com/tkrp-traction-control-button-switch-45-3533-0-9-01). This is the same unit Nicky Hayden is using on his Ten Kate race bike. €402.32!


MOTEC - Motorcycle Handlebar Switch Gear (http://www.kempower-motorsport.com/index.php?dispatch=products.view&product_id=6342) €461.00


Versatile 5 button switch (http://www.bikesportdevelopments.co.uk/ProductDetails.asp?ProductCode=BD%5FSW%5F5B%5FSPx) £235.00


EVOTECH (http://www.ebay.it/itm/EVOTECH-PULSANTIERA-SINISTRA-5-BOTTONI-NERA-UNIVERSALE-APRILIA-RSV4-FACTORY-R-/370747752687?pt=Ricambi_e_Accessori_Moto&hash=item565249c0ef#ht_3796wt_1162) €266.00


Motorcycle ATV Bike Scooter Offroad 7/8" Switch (http://www.ebay.com/itm/Motorcycle-ATV-Bike-Scooter-Offroad-7-8-Switch-Horn-Turn-Signals-On-Off-Light/201117023851?rt=nc&_soffid=5012883509&_soffType=OrderSubTotalOffer&_trksid=p5731.m3795&autorefresh=true) $5.68


Red Universal CNC Stop Kill Switch (http://www.ebay.com/itm/Red-Universal-CNC-Stop-Kill-Switch-Pit-Pro-Dirt-bikes-ATV-Quad-Motorcross-22mm-/252258493417?hash=item3abbc723e9:g:jswAAOSwAYtWMzR L&vxp=mtr) $16.66


Universal Engine Stop Start Kill Switch (http://www.ebay.com/itm/Universal-Engine-Stop-Start-Kill-Switch-Button-Enduro-Supermoto-Off-Road-Bike/111957017351?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D36499%26meid%3D4605799e222f46e695660208ae45 5d18%26pid%3D100005%26rk%3D1%26rkt%3D2%26sd%3D2521 48535395) $14.99


04-29-2016, 12:41 PM
Yesterday I visited a bunch of moto shops looking for bits and what not. At Monroe Motors I spied this Ducati. The interesting think about it to me is the shock mounting. They mounted the Ohlins in the same fashion that I did on my GPR. Vindication! Only they have their sticker oriented in the proper fashion. Maybe I can source a new sticker. :P


In the evening I trekked out to Speedy's place for some tire action. We changed four tires, and reseated one of the tires that's currently on the Silver bike. Was a good bit of work!



And here's a little sneak preview of something very nice. Sorry for the lame photo--better ones are sure to follow. :)


04-29-2016, 01:10 PM
The 125 2T air box showed up from EZ Parts. It's much nicer in that the top is screwed on rather than the snaps that never really worked on the 50cc air box. Also the inlet has the larger adaptor, and the boot to the carb is larger to accommodate the larger carb. Only it's not large enough for the PWK! So once again the rotory tool was brought into play. :P





I had also hoped to do a mod to the mounting to make it easy to remove the air box on the bike. I did the mod, but as it turns out you still have to completely remove the subframe in order to install the air box. The air box engineer really should have come up with a better solution for this one. :(



04-29-2016, 01:45 PM
I'm just going to leave this here...


05-01-2016, 03:43 AM
I worked on a Gilera 125 a couple of weeks ago, man that airbox is a struggle! It took me a couple of hours to clean out the carb, whereas it's a 5 minute job on my RS/TZR hybrid.. Is there not a bit more trimming you can do to allow it to slip in through the frame a little easier? it'd drive me mad having to do all that work when it came to jetting a bike..

05-01-2016, 05:55 AM
Working on the carb isn't such a big deal because you can just loosen up the clamps and spin it--say for jetting. But near as I can tell there's no way to trim the air box so that it can easily be pulled, and by that I mean without removing the subframe. I was thinking to build a fiberglass unit that would sit under the tank, but I ended up passing and getting the 125 box. It's better than what was there. :P

I also picked up the 125 hugger--which is slightly wider than the 50 hugger. It's amazing how inexpensive the non-painted body parts are for this bike. I think this hugger was around $9! :)


When fitting things today I noticed this moto rider on the Sava MC50 rear tire.


05-02-2016, 02:45 AM
When I was crashed the cowling was broken, and many of the bits that go with it. Thankfully you can get a lot of this stuff for low prices from EZ Parts, but the cowling itself was an expensive part to buy. Recently on the eBay one showed up for an amount that was affordable. :)

I'm still waiting on some of the bits, but there's enough old and new to start with the assembly. The windscreen was messed up and needed replacing. They look so nice when they are new.


A quick mock up.


I picked up these nylon screws for the windscreen. They work, but I think I'm going to replace them eventually.


Here's the cowling with part of the support, and the windscreen in place.


And again with the lamps--like before I'm using stainless steel screws. You actually have to put it together in this sequence, or it wont go together. :eek:


Thinking about where to mount the EGT gauge. I'm going to have to fashion a bracket for it. Time to visit the plastic store again. ;


As it comes together. :)


05-04-2016, 01:40 AM
The bolts came today. :)


I can't believe how much Airsal I've bought over the years. This isn't even all of it!


Such a nice pipe, it's too bad it doesn't fit the bike. I'm going to have to modify it to work, so for a while I wont be able to use it. :(


Ready for wrenching. :eek:


05-04-2016, 04:04 AM
Had a little more time tonight and the stage was set for some forking around. :)

Interesting to so the difference in length of the older GPR front axle and the newer one.


The throttle side forks--the stock Sebac and the Paioli.


To orient the forks there is a flat area that is placed on the inside.


The throttle side fork in place.


The brakes side forks.


The brake side fork in place.


The look so nice sticking out of the triples.



They are going to be very nice. I do hope that the spring can support my weight. :eek: And I do mean spring, as only one fork is sprung.


05-04-2016, 07:14 PM
Now that the forks are finally in play I can get to the brakes. I finally found a nice rotor for the GPR. And a better AJP caliper--well the same just matches the forks better, and well EZ Parts had available a nice stash of front end parts that just seemed like the right thing to do. If anything I probably should have gotten more of them. But I did notice that some of the newer stuff isn't of the same quality of the older stuff. :(

First up was cleaning. Derbi uses pretty tough thread lock on the brake disc bolts. If you don't heat them up before trying to remove them you are likely to brake them! But it's also nice to chase the threads with a proper chaser when doing brake stuff. ;)


Mostly cleaned up.


The Bolt Depot order was rather small this time. But I did get some neat bolts for the brake discs.




Just about there...


:) Looks so nice. Nearly impossible to get the actual color of the disc in an image. It's more of a fluorescent red/orange.


OEM axel bits, and the wheel on.




Brake bits. If you do this mod make sure to order the 125 bolts (or source them) as they are longer than the 50 brake caliper bolts.



The caliper came with new pads, but the Ferodo pads are so much better. The ones in the old caliper were a bit glazed. I would like to have ordered new ones, but I just don't have the resources. So I worked at cleaning up what I have--they came out pretty good. ;)




And sitting on the bike. :)


05-04-2016, 11:39 PM

The unpainted bits are so inexpensive, but this cowling support piece did need to be replaced as the crash to brake it.





Notice the slot in the fork to allow the disc bolts to pass though.


The fender supports were in pretty bad shape so I sanded them and shot them with some black paint. ;)




I still need to get this sorted, but the Fibaaa is going to be very nice. ;)



05-05-2016, 08:18 AM
That looks really awesome! Cant wait to see it completed...:plus:

05-06-2016, 03:54 AM
Hey M, yeah thanks for the support. It's pretty much been nearly four years getting this bike back together. I'm so excited I could burst!!! :lol:

Today I got a bit more put together. Got the brakes working, messed about a bit with the electrics, and I think I have the carb mounting sorted!

When I first got the bike the reg/rec was broken. I couldn't source the proper one so I used one from an older GPR. The swap over was pretty straight forward, and only required the use of a Y connector since the newer one has one more pin. Here's the schematic of the newer bikes, photos of the older reg/rec on the bike, and now the proper one back on the bike for the first time since I've owned it. :eek:






The next step for today was getting the front brake functional. This was actually much harder than one would expect. The banjo bolt in the old caliper didn't want to come out. It actually rounded out inside the bolt. This was after using heat too. So I had to get the impact driver and hammer, and I have a 5.5 allen socket, which came in quite handy today. More heat, and some force and I was able to remove it. But this meant that I couldn't use that banjo bolt, and I really didn't have a replacement. I needed to do this in order to get the brake line from the old system to employ it on the new setup. ;)

I did just order several rear brake banjo bolts for the Derbi bikes from EZ Parts. These are special because they have the bleed screw built in--which means that you can't use anything else with those calipers (easily anyway). I ended up enlisting one of those banjo bolts on the front end. Now there are three places from which to bleed the brake. I ended up using all three too. And they all use a different size wrench 7, 8, and 11mm just to bleed the front brake!

I should probably mention the RCS15 as well. It's is so pretty on the bike. The closer I get to getting this bike together the more I just want to keep it inside away from all the assholes that keep running over my bikes. :eek:






One issue I keep having with brake bleeding is the line winds back up. I came up with running the tube through a wrench, and this worked great. :lol:


I keep finding all these neat things on the Sava's. :lol:


I ordered some new mounts for the plastics and they came in black. I should have ordered the lower ones too. Maybe have to order them later.



I had to take this photo because it was looking so nice. :)


The carb mounting is finally coming together. I have to stretch things a bit to get it to work, but it seems that this may be the solution.



05-06-2016, 11:28 AM
Dude !
That front braking system is PIMP !
I Love the new rotor / caliper, and the banjo bolt/bleeder is GENIUS !
And of course, the Brembo is just all kinds of sexy !

I'm anxious to hear your thoughts on the CP carb, as well.

05-07-2016, 02:23 AM
Yeah RJ I'm excited to get to ride this bike once again. Been way way way too long. Of course there are so many things to sort out since I've changed so much of the bike. Tires, top-end, crank, carb, air box, suspension, brakes, on and on. But it will be lots of fun too. :)

That carb is actually the PWK Polini. I have a CP, but it's not intended for this bike. When I get it connected I'll let you know about it. Ed did just put one on the RS he picked up from Greg. That bike has Matt's Top engine in it. Ed would have been riding it tomorrow, but we got rained out. :eek:

Okay some more moto Pr0n. :) I got the new chain out and installed it. It's a nice looking DID. It was the best chain that they had at Treats. Hopefully it will be up to the task!




Here's a shot from yesterday that I couldn't include because I hit the limit of photos allowed in a single post! It's the inlet of the 125 air box. ;)


05-07-2016, 06:43 AM
It's amazing how close the tolerances can be with these things. :eek:

Today I went to Tap Plastics to pick up some plastic for making mounting locations for the other gauges. I liked this piece because it has a nice texture.




Before making the mounts I need to make sure things would fit, and I found that things were much tighter than I had expected. :eek: It's going to take some serious fiddling about to get this all to work.






I also got some time in on the carb. Took some photos of the needle (PW24). The throttle is hooked up to the carb, but the carb isn't as smooth as the Metrakit carbs. I may put one of the Metras back in the bike. Also, here are the clamps that hold the carb in place--well the air box side anyway. ;) They both use a 7mm socket to actuate. The intake side comes with the Malossi intake, and the air box side didn't actually come with the air box. It has to be ordered separately.





05-07-2016, 12:27 PM
This is looking so good Tora, great work, will be lush.

Sent from my HTC One using Tapatalk

05-08-2016, 01:34 AM
Thanks AP! I am working hard to make this bike something special. ;)

Today was another one of those rough days trying to find all the little bits. I finally gave in and worked with what I could find. :eek:

As another taking advantaged of the nice price of non-painted body parts from Derbi I ordered new intake vents. These got messed up in the crash too.




Next up was working out the mounting of the Stage6 EGT gauge. Yesterday I made it out to Tap Plastics to get some raw material. With a little bit of measuring and mocking up the mounting was accomplished. ;)









05-09-2016, 12:41 AM
So of course I wouldn't be happy with only EGT. :lol: But the solution to the other gauges has put me in a bit of a stall. I have a nice little Daytona gauge for water temp, but I can't seem to find it! Thus I've given up on it (for now). In addition to EGT I also want to equip the bike with water temp, and head temp. Koso makes some nice gauges that I like and they come in both blue and red displays. I'm probably going to go with them eventually. Run the blue for water temp, and the red for head temp. But that doesn't get me on the road as quickly as I like so what to do? For now I'm going to give up on the water temp, but I do have a Trail Tech CHT gauge.

I'm not much of a fan of these gauges. They are not user serviceable, they depend on an irreplaceable battery, and the element that is fitted between the plug and the head fails, as it would appear, just by looking at them! :eek: They are also hard to read (at speed), and there is no easy way to illuminate them. But it's what I have so I'll employ it for now. They use to only come in silver. These days they come in black, but since I have a silver one I need to deal with that issue. I cleaned it up, taped it up, sanded it and shot some black paint at it. The paint didn't cure very well, but again it's only a temporary solution.





For now this is where I've located it until I get a couple of the Kosos. ;) It's held in place with some actually Velcro!



05-09-2016, 07:13 AM
A couple of photos I meant to post some time ago...



05-09-2016, 09:29 PM
Damn, Tora !
I thought my gauge cluster was crowded ....


05-09-2016, 11:44 PM
Yeah RJ I have to get super creative to get all this stuff happening. :lol:

Several of the parts I've ordered aren't what I ordered. For instance check out these valve stems. Derbi employs a slightly shorter valve stem. When you install a standard stem you find it troublesome to check your tire pressure. I found this out when I had the wheels powder coated for the Red bike, and installed new standard stems. Because this is such a pain I ordered some Derbi stems, and guess what I got sent. :eek:


Another size matters item are the little spacers employed for the bar ends. The older GPRs use a slightly larger spacer. When installed on the newer GPR it just looks wrong.





Had some tiding up to do around the engine compartment.



Because it was time to installed some Yamaha tech. :)











05-09-2016, 11:54 PM
Here's another sweet little item I picked up a while back. :) The stock shifter doesn't hold up very well. I had replaced it with this cook Metrakit shifter, but it only functions in GP shift, and for now I'm not quite ready for that mode again. :lol: So this is a nice compromise as it properly matches the brake lever.


Speaking of brake lever--it's finally time to get the other peg installed. That required a bit of "lathe" work. It's nice to have two proper pegs on the bike.




So many things are pretty much there on the bike. Once I put some fluids in, finish up some wiring, I'll be almost there--but the pipe...

The nice Voca pipe isn't ready for action yet, so I'm going to use the Jolly Moto, but it doesn't fit too well, and I have to create a couple of brackets.



05-10-2016, 12:02 AM
"Air Chamber System" = " boost bottle" ?
Haven't seen one of those for awhile !

05-10-2016, 12:12 AM
They are also sometimes called resonators. They work on similar principles as the expansion chamber, only on the intake side. Yamaha puts them on nearly all of their strokers, and they've published white papers on them. The tube length is how you tune them to your engine. You basically want the capacity to be the same as the displacement of the engine. What I probably should have done is filled it up with dihydrogen monoxide, and measured that in a graduated cylinder. But I didn't. :P

As for performance, they help with the midrange a little bit. ;)

05-10-2016, 03:05 AM
There are some things about this bike that I was truly enamored with when I saw photos of it for the first time. The mirrors, tires, brakes, and more. It's funny because many of those things I've replaced. :lol:

Tires were easy because well they wear out, and you become a better rider and want better tires. Brakes were another thing. The radial brakes were attractive, and then I had to upgrade those. The mirrors were so cool with the indicators built in. The problem with them is that they break when you look at them funny.

I had thought about using the Aprilia mirrors because they had them on AF1 for $15 each. That's a great price. RJ did some measurements for me, and they looked pretty close. Then the price went up to significantly more for each mirror. That axed that option. The other night I was moving some parts around, and in the stack was a pre-gen GPR mirror. I tried it and well they look pretty good. The remaining issue is indicators. Still working on that one. ;)




05-10-2016, 07:37 PM
Looking great !!!
So many sweet parts, loving the Rotor !!!

Here's a quick "cheat sheet" for Boost Bottle tubing ...


05-10-2016, 07:54 PM
It never ends, or so it seems. :lol:

The stock mounting bolt is an M5, but this fender is for the RS4, so I don't expect all things to be the same. But the hole was even smaller than an M4!


It looks like I'm going to have to find a solution for the throttle cable vs the resonator.


05-10-2016, 08:16 PM
Some REALLY interesting info here:

05-10-2016, 11:59 PM
Are you gonna use the Domino switch for the right hand switch gear, or go all left handed ?

05-11-2016, 03:19 AM
I have the domino switch that I picked up for the right side. It features a kill switch, and a momentary switch for the starter. I don't have a starter on this bike because I'm running the HPI ignition--so it's all GP Start for this bike. ;) But I don't know if there will be much room for the switch as things are really tight up there, but we'll see. ;)

Got the fuel line and filter installed.


I also modified throttle cable. This was a total pain in the ass, and I'm not very happy with the current solution. It clears the resonator nicely, but now I'm getting a sticky throttle, and well I wont put up with a sticky throttle!!!


It's getting so close!


05-12-2016, 02:53 AM
It's coming together very nicely! That motor looks especially trick...I like it..

05-12-2016, 08:47 AM
Thanks Martin. I had that engine built up last year (you can see photos of it on the kitchen table). But I ran out of money and had to wait. :eek:

You know you've been up too long working on your bike when you hear the birds singing. :lol: I'm truly amazed at how long everything is taking to accomplish. It's all a bunch of little things, and they add up to a whole lot of time. :eek:

I can't seem to get any of my performance pipes to work with the frame and body work. So I pulled out the Ninja pipe that I have for this bike. It's not a bad pipe, just not the kind of performance that I want for this bike. But it will work until I can get a better pipe. Once I knew which pipe was going to be employed I got to installing the EGT sensor. It went together fairly well considering the Stage6 directions don't tell you any specifics. I knew I wanted to set the sensor about 15cm from the piston skirt. A bit of measuring things worked that out. I didn't know what drill bit to use so I started small and worked my way up to what looked right--which happened to be a 1/4".



I didn't grind off the ridges like RJ did (I'm too lazy!), partially because the spring clip is about where the sensor should go. I ended up putting it a little bit off axis which is fine, and I located the clamp to sit on one of the ridges. Worked out okay. This first photo is checking it out, the second one is the bung installed, and the third is on the bike.




A little RANT time. What the hell is up with battery companies. They make these hi-tech batteries and stick these horrible connectors on them. Hey Shorai you are a fucking JAPANESE company. You have JAPANESE engineers. Your ancestors must be turning over in their graves for putting out such a horrible design. Seriously!

It's hard to see in the second photo, but I finally got so fed up with this crappy design that I went and got a piece of hose and stuck it under the nut. It's an old trick that works a whole lot better than what Shorai came up with using a piece of foam. Ballistic did a much better job at the battery posts.



So I went for the switch! Things are so tight in there that it is questionable! And I couldn't employ the neat design on the switch to work with the throttle. But that's fine. The only part of the switch that I was going to use was the kill switch. While I was working on this my buddy Jason called me up. He was out Gromulating. Some idiot creeped up his ass at a stop light. We were talking about what to do about assholes like that--and well really all you can do is let them pass. But one thing that it made me think of is how it would be nice to have a button to flash the tail light, and well here I was wiring up the brake switch to the tail light, and I had the momentary button from the starter on this switch gear. So I wired it up to the brake light too. ;)



To get the wiring together I had to make two custom harness adaptors. It took a lot more time figuring out how to design them than it took to wiring them up. Lots of thinking about the wiring diagram, pinning out the things like the switch gear--all that sort of stuff. Took many amounts of time. :eek: And they ended up looking a bit scary too. I really didn't have the right parts to make these--if I had they would have looked much cleaner. I had to scavenge bits from here and there, and well at least they work! :lol:




When I got the bike it didn't have the front running light. I've always wanted that to work. The standard setup for it is to run it only off of the stator. I wanted it run off of the battery so that it was always on--like at stop lights and such. I really don't want to get hit again! Anyway it works now. :)


And the real pretty sight--a working EGT gauge. :)


05-12-2016, 10:07 AM
I am soon going to (probably) face the same 'space' issue on the right hand controls, as I have the same setup to mount - Domino throttle, Domino start / kill switch, and Brembo master. Waiting for a front caliper rebuild kit before tearing into that whole can of worms. Not that my caliper is problematic, but since I will be changing all the other front brake components (Brembo master cylinder, Ferodo pads, Galfer lines, new fluid) ... may as well renew the caliper as well.

I got so fed up with needing so many things grounded, I made a 'central' grounding location. When I installed the TP (red) variable CDI unit, I needed a couple grounds, so I ended up making a plate to mount the CDI, and attached it to the frame, then mounted a terminal block with it grounded to battery, and now I run all my grounds to that. I'm thinking I'll do the same for the dash area, since I will need power / ground for both my EGT and my (soon to be) CHT meters.

As to the tail / stop lights, I did the 'halo' tial / brake light mod that Xero did, and I think it is one of the best mods I ever did. I am WAY more visible from behind than ever. I used a 'standard 1157 LED replacement, with a 50 mm halo LED set ( I found 'em on Amazon, 2 of 'em for like 6 bucks). I didn't use any resistor, as I LIKE it being so damn bright.
In fact, I did this in conjunction with replacing the stock RS50 headlamp with one from a RS125 (thanks, DcRac3r !) and ended up going to ALL LED bulbs for turns, tails/brake, running lamps, dash lamps, etc. The only weirdness was having to use an 'electronic' flasher, instead of a mechanical one... and I couldn't get one with only two posts at my local auto store, so I had another use for my central grounding location :)

05-12-2016, 08:48 PM
Hey RJ, getting the brakes all nice and happy is a great thing. :)

I didn't think to do a ground plate. On the Derbi they have a bundle of yellow/green wires that feed ground to everything. I try to keep my wires in line with the stock stuff so that later when I'm trying to figure out what I did it makes sense! :eek:

I still plan on putting a couple of Koso gauges on the dash. One for water temp, and one for CHT. I like that they light up. Red for CHT, and Blue for H2O. :) Since Stage6 and Metrakit things are really Koso parts the connectors and temperature scales all remain the same. The gauge is just shy of 6cm x 3cm. Should fit nicely just above the speedo. ;)


The tail light on this bike is a bit strange. I did get a new one from EZ Parts, but haven't installed it yet. I don't know if the halo would fit in there. I'll have to see what can be done. I also don't really like the look of LED head lights. The stock halogens are pretty nice on this bike--of course even at 55 watts it wasn't enough to make me visible to the woman that crashed me! But what intrigues me is that electronic flasher of which you speak. One of the things about the Derbi that's both really cool, and a pain in the ass is that the flasher is built into the Reg/Rec. Makes for a nice small foot print. But also means that it's more expensive when it fails. I'm not a fan of the charging system on this bike so I've been thinking about a Reg/Rec upgrade (even though I just put a brand new Reg/Rec on the bike), but the thing slowing me down a little bit is the flasher. I think you can see where I'm going with this one. ;)

Another temporary solution. I had to have something for front blinkers. These goofy little LED blinkers came with the bike on the tail section. The PO thought they looked cool. I thought they'd get me pulled over in CA. ;P So I put some stock Derbi blinkers from another GPR on the bike. That too was somewhat temporary. :lol: I hunted all over the bike looking for the best way to mount these. I decided on this spot because the white finish reflects the blinker making it look larger than it is--eventually I'll come up with a better solution.


Oh and I think I'm ready to start testing the bike. Just need to get some folks to help me get it down the stairs...

05-12-2016, 11:21 PM
When I got this bike it was almost new. Heavy emphasis on the almost. There were enough things that were messed up, and in such a way that I didn't even know about it. Getting the parts manual and many hours of looking through it, plus lots of experience with the bike--and now with EZ Parts the ability to actually order honest to goodness Derbi parts has changed things a lot!

Notice this rubber bumper and the spacer. These go to the front of the fuel tank. They were not on the bike when I got it. Installed the tank now sits better and is secured way better! The bolt is a 45mm M5. I'm probably going to source a nice button head bolt for it. ;)





I've noticed that the front brake isn't keeping pressure. I found seepage at the top bleed on the Brembo yesterday and tightened it up. Today I found that it's still seeping and that the hose I employed for the reservoir is sweating! It much be fuel line that I mixed up with brake line. Not happy! :eek:



05-13-2016, 05:30 AM

05-13-2016, 12:13 PM
Tora - for your tank issues, you might consider a part from an Aprilia RS50 -


It might require a 'massage since your stock bolt is M5. From the parts diagram at AF1...
15 AP8150202 Hex socket screw M6x50 1
16 AP8121819 Washer 6,5x12,5* 1

05-13-2016, 04:04 PM
The ones on the RS4 look even prettier. ;) But I don't think either of them will fit on the Derbi tank with this bike.



05-13-2016, 07:54 PM
The newer Derbi employs these multi mini blade connectors. Anyone know where to get them for a reasonable price?


05-13-2016, 09:09 PM
I've had pretty good luck with automotive stuff from 'Painless Perfromance'...

05-14-2016, 03:58 AM
Thanks Randy I'll check it out. :)

I keep messing around with the brake master. Got some new hose today, and re-bled things a bit. Waited a bit and found things were still leaking. Worked on it a bit more so hopefully tomorrow it will be better.

Took some fun photos. :)



05-14-2016, 05:26 AM
Found this on Power Sport Tuning (http://forums.pstuning.com/index.php?showtopic=1559)

I've never read or heard a good explanation... so I can only share what I've learned over the years. If you understand what "piston wash" is, then it's pretty easy to know what to look for and what to look out for.

The first thing you need to realize is that the top of the piston is not a uniform temperature. The area in front of the exhaust port that is exposed to all of the hot gases exiting the cylinder is naturally the hottest. The area in front of the transfer ports that is cooled by the fresh air and fuel entering the cylinder is obviously going to be the coolest. And, the center of the piston will be somewhere in between.

The second important thing is that there is some small range of temperatures where the piston is hot enough to char the oil that comes in contact with it, but cool enough not to melt the piston.

Putting those together, you have "piston wash".

When the engine is jetted very rich, most of the piston (except near the exhaust port) is too cool to char the oil; and you will have large areas spreading out from the transfer ports that appear to have been "washed" clean of carbon by the air and fuel entering the cylinder... that is "piston wash".

If you jet down leaner, the temperature of the whole piston will increase... and more areas will be hot enough to char the oil. The "washed" areas will be large circular areas, located just in front of the transfer ports. At this point, the center of the piston is quite hot; and is actually charring the oil on the underside of the dome, right in the center.

Jetting down further will cause the whole piston to get still hotter. Now, nearly the entire piston is hot enough to char the oil... and the "wash" will be just a small area about the size of a half of a dime, right in front of each transfer port. The bottom side of the piston will be charring the oil over a large area by now also. At this point, the area near the exhaust port is getting almost hot enough to melt. This would be considered (at least by me) to be jetted correctly... but near the "edge".

If you go leaner yet, the whole piston will be hot enough to char the oil on top of it and there will be no "washed" areas left. The entire piston will be covered with carbon, and the aluminum at the edge of the piston, right in front of the exhaust port will actually be slowly melting away and smearing onto the rings... more than a few seconds of this and it's time for new pistons.

That, for whatever it's worth, is my own twisted look at piston wash.

Some things to keep in mind include the fact that the size of the "washed" area depends somewhat on the upward angle of the transfer port. If the port is angled flat across the top of the piston, there will be more cooling and more wash... in spite of the fact that the area in front of the exhaust port might be just as hot as it would be on a motor with upward angled transfers that shows much less wash. The upward angled transfers don't cool as much of the piston top.

Also, the size of the "washed" area has to be somewhat proportional to the size of the piston. A "half a dime" sized wash area on a 600 triple (very small piston) means the piston is a lot cooler than a "half a dime" sized wash area on an 800 twin (with coffee cans for pistons)! What you're really interested in is how much of the piston isn't clean, because that tells you how much of the piston is hot enough to char the oil... and you know the exhaust area is hotter yet.

All this really means is that you can't just say, "Every motor should have a half-dime sized wash area." You have to correlate the size of the wash area to other indicators and engine specs... and use it as just one of your tools for jetting.


There are lots of ways to do this, but a borescope is kind of nice. This one is pretty inexpensive (http://www.amazon.com/BlueFire-Android-Endoscope-Phones-Function/dp/B013HZCYXK/).


05-14-2016, 06:57 PM
Got the bike out the door, fixed a few minor issues, and started in on the heat cycles. :) If things go well I'll get to ride it on Derbi de Mayo (http://www-gprcamp.rhcloud.com/?p=263)! I'll probably be taking it for a test ride later today. :) Then a bit of tuning to make sure things are in good shape. The bike started right up, and is running great so far. The throttle response is fantastic.


05-14-2016, 11:03 PM
I JUST bought one of these 'borescopes' that connect to your phone!

05-14-2016, 11:06 PM
Looking GREAT, Tora !!

05-15-2016, 12:36 AM
I ordered one of those scopes last night. I'll have to pick up an Android device for it--but since you can pretty much get them for free it shouldn't be a big deal. ;) The bigger issue is picking out the software to employ with it.

I have a bunch of photos to post, but PhotoBucket is currently doing some wrenching on their site. ¯ \_(ツ)_/¯

I took the bike out for a test ride. It's jetted way too rich so it's actually difficult to get it on the pipe. You have to execute precise throttle control. Currently there's a 112 jet in the PWK. I'll start dropping it down tomorrow.

Another issue I'm having is the tach has gone completely wacky. The calibration of where zero is changes every time the bike is switched on. I have tachs from older GPRs so I might implement one of those.

05-15-2016, 06:29 AM
This bike is just amazing!

05-15-2016, 02:56 PM
Hey ESP! I've been wondering where you've been lately and how your project is coming along--post some updates! :) I hope you'll have a running bike in time to bring it to GPR Camp. It's now less than a month a way. It's all very exciting. :)

PhotoBucket is working again today so lets post up the photos from yesterday. The house seems so empty now that there's not a bike in it. :lol: These are the steps we had to traverse to get the bike out. It actually went pretty smooth, because we took it quite slow. Brendan and Alex came over to help. :) The bend at the landing was tricking because the bike had to actually be on the steps before the landing and after the landing to make the turn. After that it went pretty easy. I left the seat off for some nice handles, and the lower plastics too. The pipe did scrape on one of the steps but we were careful and lifted it over that section. :eek:




Once outside I put some fuel in the tank. Upon opening the petcock fuel started leaking out! :eek: Turns out that I needed to get a wire tie on the fuel line at the carb, and the rubber gasket for the fuel filter had fallen out in the house. Found the problem, found the part, put it all back together and things were fine. :)


With fuel in the bike I went for a start and the bike started right up first try.


Not a lot of space left for the idle adjust screw. May have to go to a different slow jet. But I have also noticed that the tach isn't telling the real story. :( Probably going to have to replace it.


Here's a bunch of photos of it out of the house. I still have to clean it up, get all the plastics on it etc. There's a bunch of work to do yet, but at least it's running again. ;)









The Deliverator! And of course there's the celebration. :) Went to the pizza joint and got a large cheese.


05-15-2016, 05:33 PM
If Hiro Protagonist rode a GPR.....

05-15-2016, 06:30 PM
RJ, the way I remember the story he did! :lol:

Bunches of little things today. I noticed I forgot to put springs on. Well I didn't actually have the right ones, but I found something to work for now. I'm just glad I fit the pipe on well enough that it didn't leak even without the springs! When I get things set up with the other pipe I'll use proper springs and all new hardware. :eek:


Dropped down to a 108 main jet from a 112. Yesterday's test ride illustrated it was just too rich to easily get on the pipe. Hopefully things will be better now. Picked up this sweet Polini Jet Pack. Too bad it's not the kind that goes on your back! Readjusted the air/fuel mixture, and idle as it changed a little.




A fun shot while setting the idle. Notice the numbers 46, 93, and 99. :lol:


Adjusted the chain (it's new and stretching), also tightened up the engine mounting bolts. I noticed some vibration yesterday, and sure enough the bolts needed torquing.


Test ride eminent.


05-16-2016, 12:49 AM
I must say this is a weird one. With the 108 it still had major issues getting on the pipe. The 106 has issues too, but it gets on a bit easier, with a bit of hesitation just before it gets there, however still struggles in the higher gears. It's like this hump that it has to climb over. When on a hill where it has to pull getting over that hump seems insurmountable, and to get beyond it I've had to down shift to get the speed high enough that when I bring it back to the higher gear it has made it to the point of being on the pipe. I'm really disappointed that the tach is going crazy. It sure would be handy to have that information right now!

But I've got probably the most complicated GPR engine I've tried to run so far. It not only has a hyper kit, with the 24mm PWK, and a pipe there's the fancy ignition, and the boost bottle all mixed in there too. So I know I'm getting some pretty crossed signals. Temp wise it does get quite hot climbing the hills. The head temp is hitting around 110°C, and the EGT is getting past 1100°C. When I see those numbers I stop pushing it. I mean the engine is still pretty fresh so I need to be some what mellow with it. :P

This plug was with the 108, but I didn't do a proper chop with it so all that it tells me is that over all things are rich.


I've fitted a 104 for testing tomorrow. I hope I find the proper main jet soon as I've only got a 102, and a 100 left!

The suspension is quite dreamy. I can see that once I'm not having to place so much attention to the throttle this is going to be a really fun bike to ride. The rubber isn't quite scrubbed in yet, but so far the bike is taking every corner quite well, and I'm already able to push it harder than I can push the Silver bike.

Idiots. What is it with these fooking idiots that want to drag race me. Dude it's a FIFTY if you beat me so what, and if you get beat you are going to look like a total loser. Some wannabe loser in a Fiat Aberath(sp?) gunned it on this road that goes from two lanes to one. If the bike was running right I might have just seen where he'd give up, but really I probably just would have done what I did do--which was let off the throttle and let him go by. The road leads to a section where the cars have to stop and I filter past them on the bike anyway so it really doesn't matter. When I was filtering by I looked at him and pointed to the part of the bike that says 50. I don't think he got it because he tried racing me again. I just let him go--what's the point? :lol:

Snapped some photos up on Twin Peaks at a spot most folks don't shoot. ;)






05-17-2016, 06:51 PM
Some fun stuff today :)

I've seen the other Motul oils come in the gallon size, but it looked like you couldn't get the 800, well I found out you just have to look for it!



05-17-2016, 07:02 PM
Okay hit the wrong button, or the right one too soon. The other fun stuff today. :)

So the front running light on this bike employs one of these--I think I need to source an LED version as this one, small as it is, seems to be totally down with draining the Shorai!


The little Koso showed up today too--Feel the Speed. I'm totally surprised by the speed considering this came from Asia! But hey that's their slogan. The connections look a bit anemic, but hopefully they'll hold. Maybe put some silicon sealer on there or something. It should also tuck away on the dash nicely. ;)






As for the running of the beast today I tested the 104 main jet. It's better, but there's still enough hesitation getting on the pipe that I'm going to swap it out for the 102. After that I only have one more jet to swap out! I am so looking forward to this bike running properly--it's just going to be so much fun. Yes that CHT says 27°C, and that's in the shade! I feel like I'm wilting :eek: But it's getting late enough in the day that there will be more shade soon so I'll finally be able to do some proper wrenching. :)

05-17-2016, 07:50 PM
If I recall, this is the bulb I fitted -
On the Aprilia they call it the 'city light'


But they have a lot of different options. I did all the gauges and turns with LEDs from these guys

05-17-2016, 11:09 PM
Hey RJ--Well I can see the trick is going to be selecting the color least likely to get me pulled over! But damn $13 for one tiny little bulb? Really?


So I'm at a bit of a conundrum. When I dropped down to a 102 it didn't run any better. I pulled the plug and I could see that the tip was silver! Exceedingly lean. It's harder to see in the photos but the same side of the insulator is also more lean than it was with a previous jetting. Now this is with the head that's not the right one. I had to place a bunch of base gaskets in there to get the right squish--which is pretty close to 1mm, which means that all of the ports are opening up about 1mm sooner. Now this could explain the bikes hesitation to get on the pipe.



Of course it could be the timing, as it is possible that I didn't get the ignition timing correct--although I think I did--but I didn't make any offsets for the advancement in the port timing. This all means to me that I have to take a big step back and wait until I can fit the proper head--or maybe stumble upon enough knowledge to put some more puzzle pieces together. :(

05-17-2016, 11:21 PM
yeah... 13.00 is a bit much. But I'm not the one who is never seen by drivers, either ... <pokepoke> :)
That said, I've had the back wheel WAY in the air more than a few times ....
Seems like we're both having tuning 'fun', although I think I may have have it a bit easier with a pretty 'known' setup.

Lemme know how I can help ?

05-18-2016, 09:44 PM
that looks way too rich

05-19-2016, 04:18 AM
Looking at the plug I would suggest retarding the timing. Normally the burn back on the center electrode should only be right on the end and perhaps 0.5mm down towards the ceramic, not as much as yours. This could explain the heat factor.

Have you tried dropping the needle at all? Sometimes that flat spot just before the powerband is really sensitive to richness on the needle, you may find just half a clip would help here (make your own shim from suitable metal).

05-20-2016, 02:49 AM
Yesterday I pulled off the kit--it's just never going to work without the right head, and who the hell knows if it will ever show up. I think I'm done with Airsal. Their products are nice enough, but the customer service is horrible. How much stuff do you have to buy from a company to be considered worth supporting? All they had to do was send me the proper head for the kit. I didn't pack the wrong stuff in the box--they did that, and it wouldn't have cost them hardly anything to fix it. I've sent them numerous posts via their website. They never once wrote back. But they did contact Treats about it, and apparently that didn't go all the well either. Here it is well over a year and I still don't have a workable solution. :(


Tomorrow I'm going to try another kit that I put together from pieces yesterday and today. Greg gave me an engine for the Senda. It came with a ProRace top end, but wasn't running right. Calimari once had some Metrakit stuff on sale--parts left over from their racing days and I picked that up. And a while ago I found some Metrakit rings on teh eBay. The wrist pin and clips are from another kit, but look like they'll work well enough. All the rubber bits are from various kits too. ;)

Yesterday I got out the Swimming Pool Acid and cleaned up the barrel. I also installed the adaptor and temp sensor for the Koso gauge.





05-21-2016, 02:43 AM
Lots and lots and lots of wrenching went down today. We worked hard on three bikes, and it looks like all three will make it on the ride tomorrow. :)

Here's some DRP pr0n from today. :)




















05-24-2016, 09:28 PM
The bore scope showed up today. I don't have an Android device so I got out the old MSOS lappy, and installed the included software. The scope came with an adaptor dongle that allows it to plug into a regular USB port, and a simple camera app that speaks to the bore scope camera. Basically it thinks of the camera like a web cam, and it looks like the resolution is about the same too.







I pulled the plug and took a look. The camera features six LEDs that light up around the camera. These are adjustable via a rheostat on the little box that is inline betwixt the camera and the USB connector. Knowing the history of the plug this one looks like it's been running lean--don't let the brown fool you as it was there from a time when the carb was setup rich.




But really what tells the story is the piston which shows no wash at all. But the strange thing is that the engine behaves as if it is rich. The EGT and CHT temps were both rather low, and the bike four stroked significantly.





05-24-2016, 09:39 PM
For Derbi de Mayo the bike didn't run very well at all. I have quite a bit of work to do before GPR Camp!

Lost one of the front fender mounting bolts.



The rear hugger was getting caught on the silencer and pulling it off of the pipe. It got very loud when this happened!





I was a bit concerned that there would be an exhaust leak at the cylinder and there was. One of the previous owners had done the mod to allow standard GPR pipes to fit. The ProRace isn't machined for that because they expect you to employ the manifold that comes with the ProRace pipe and it's a flush mount.





I might go a bit stiffer on the forks as it seems to be reaching nearly full travel.


05-24-2016, 09:41 PM
drop the needle a click, go down 2 sizes on the main jet, turn the air screw out one full turn, and a colder step spark plug

from there see if you just ride it around nicely, get on to the pipe a little but don't go nuts on it

see what your egt's read after a ride to twin peaks and back, but do a leisurely ride, don't beat the hell out of her

then come on back and see what it scopes like compared to the plug look

I agree it sounded way too rich on the ride.

05-26-2016, 01:53 PM
I made an update in this thread, but it needs to be repeated. Red Racing Parts redracingparts.com takes your money and doesn't ship the parts.

Big note on Red Racing Parts (https://www.redracingparts.com)
I ordered this screen (https://www.redracingparts.com/english/motorbikesmotorcycles/partsandaccessories/aeromaxwindscreenswindshields/derbi/GPR50125RacingRaceReplicaDiMeglio2004.php) and a Domino choke lever assembly from them on March 23rd 2016, and they charged me for the pleasure. Today it is May 26th (65 days later) I regularly email these guys about my order--I still have not received any shipments from them! Their communication only occurs when you prompt them. They send an auto reply that means nothing, and then maybe they get back to your email. They repeat the same stuff over and over, but it always seems to be some sort of stock error and the parts will ship in "10-12 days." Notice how they actually use the exact same words repeatedly! And of course the parts never ship. This is horrible customer service.

I should also note the day that I ordered these items they showed a discount on the screen. This discount changed while I was filling out my order to a lower discount. I contacted them about it, but they wouldn't do anything. This very much falls into the bait and switch category.

March 25th

Ok, we will ship asap.

April 15th

I'm sorry for delay. However, we will ship your stuff in 10-12 days.

April 18th

We had an error in our stock and we are doing our best to speed up.

May 9th

I'm sorry for delay. However, we will ship your stuff in 10-12 days.

May 10

We had an error in our stock and that is the reason of delay.

http://www.apriliaforum.com/forums/attachment.php?attachmentid=291183 http://www.apriliaforum.com/forums/attachment.php?attachmentid=291182

05-26-2016, 01:59 PM
charge back time!!!!!

05-27-2016, 02:36 AM
Really I just want the parts, but I figured it was time to start posting about their shenanigans.

Today was one of those educational days. For instance I learned that you can program a timing light to lie to you. Well not really, but I borrowed this awesome timing light from Ed and it was set to 46° advanced or something. I didn't realize this and was having a helluva hard time setting the timing on the bike!


Making cool stuff. So I wanted a timing disc to help set the timing on the bike. I looked around and thought I can make one of these things. After some futzing about in Photoshop I had what I (thought) I wanted--but really it was a little bit too large. So I'm probably going to be making another one for the HPI mini rotor. I also printed out Matt's setup notes. :)

I took a holiday card cover and glue sticked the image to it. I then carefully cut it out. This gave me a nice timing wheel that can be held on with a magnet. I then made some markings on the rotor.







After a whole bunch of doing it wrong I slowly started figuring out how to do things like set the timing light, which direction I wanted to turn the plate in relation to the rotor--you know the little things. I think settings are pretty close now, but I'm not confident that the timing light was picking up the true RPM of the engine. So I probably need to connect the MetraKit tach to this bike, and do some more tests. Still I did learn a whole lot today, and feel more confident about being able to properly set the timing.

One trick Ed suggested was to use a separate battery for the timing light. This was a great idea, because then the timing light always had the proper amount of power. :)

05-28-2016, 12:50 AM
Did another disc, but this one too is slightly too large. This new one is 8cm, the first one is 9cm, I'm probably going to have to make a 7mm to be about the right size.



It was incredibly nice out today and GL came by to show me his new gear. Cool stuff to be sure. D-Boots, A-Star Jacket and pants. All really nice things. :) Since I had gotten the timing set yesterday we decided to go for a test ride. The bike felt much better with the timing change. I could now go from gear to gear and still stay in the power band. But if you let it get out of the power band you would have to down shift or way a really long time for it to get back in the band, and it wouldn't take much of a drop either. Like let off the throttle just a little bit and you'd have to down shift. It also didn't have as much power on hills as it should have there.

We were just at the beginning of Twin Peaks when I felt a very strong vibration. The previous times I've felt something like this meant a broken frame/engine mount. Plus we saw some water dripping from the radiator--so there might be a leak. I very sheepishly rode the bike home, which meant mostly coasting it down hill. I did notice that the vibration had a very slow cycle, and not really dependent on the rpm, but it wasn't the chassis because with the clutch in and at idle, or with the engine off it's not there. It's going to require some serious looking about.

The engine rotates smoothly, it's all properly tight where it should be, and the compression feels about right too. Just going to have to do some real good looking around.

The exhaust leak is worse, and I'll need to attend to that one too. :eek:




05-28-2016, 04:34 AM
So did you find it was previously too advanced or too retarded? satisfying to get it running smoother though, nice work.

Shame about the vibration though... it can be a lot of work to get these things set up and ironed out.

05-29-2016, 11:27 PM
Yeah I've been thinking about that--because I had to change things up so much. I think it was a little bit advanced, but not enough. I'm still not sure though because the timing light was offset, and I'm not confident about the RPMs. I've done two things to off set the RPM thing. Matt suggesting using my musicianship and adjusting the bike to the right pitch. Thanks to his help I've already got the Google tone generator set up to do just that! And today I hooked up the MetraKit tach for this bike. ;)

First I had to remove the stock clocks. It's only three self tapping screws but due to my loss of range of motion and strength it took me over an hours to remove them! The reason for removing it is because the tach wasn't function properly.




The replacement unit is a Metrakit tach. It doesn't include a speedo, but it's got a shift light (Yeaa!!), and a temp gauge. For now I'm not using the temp gauge because I already have three other ones. :eek: I have the old dash support so I had pre-figured out where I was going to place the tach, but I was to find out that it wasn't going to work there. I had to try all sorts of configurations. Eventually I came up with this setup. Then I connected up the wires. I had to make up another adaptor harness, but it seems the photo got deleted somehow. :/




With that setup it was time to try to figure out what was causing the engine vibration. First I looked at the engine mounts because that's the only thing I've experienced so far to cause this sort of vibration. They all looked good, but I did notice an oil leak at the transmission drain. I'm hoping it's just a slightly loose drain plug and not a gasket leak. :eek:




I also checked the pipe too. It's on solidly, even if it does have a bit of a leak! :eek:

I didn't see anything that could explain the vibrations. I checked the crank again by spinning the flywheel. it feels tight, smooth, and just the way it should. But if I jiggle it back and forth I can hear a noise. So I think it's either the big end or little end bearing. Using a screwdriver stethoscope it sounds like it might be the little end. Which wouldn't be too bad, but if it's the big end well that's totally going to suck as this crank has less than 100 miles on it.

But it was getting dark and cold so I had to wrap it up for the night.

05-31-2016, 01:00 AM
It was sunny today so I needed to bring out the Umbrella Girl. Today I worked on two bikes. The Lorenzo-Ui replica and the Wicked. I kind of worked on both of them at the same time. The replica went fairly well in as much as I could do with what I had around. The Wicked however, well...


I didn't take many photos, but I had to do a lot of wrenching. It seemed that yesterday I had localized things to the connecting rod. That meant pulling the top end. I thought well what if I pulled the pipe, reached in and held the piston. That indicated that the rod was fine. But while doing that I had my head under the engine (I know!). From that point I noticed that the noise was coming from the clutch side of the engine. I drained the transmission oil, removed the clutch cover, and discovered what appears to be a failing basket. I replaced the basket and almost got things buttoned back up, but it got dark and cold so I had to pack it in for the day.

I do hope this solves the problem--I so want to be riding this bike! I did take the Replica for a spin tonight though--first time really with the current setup. It was fun. :) It scoots along nicely. These second edition second gen GPRs are great little bikes. :)




05-31-2016, 08:50 AM
can you circle or explain what is broken on the basket? what do you look for?

on our larger bikes the baskets often get grooved and the fibers won't release because they get stuck in the groove

05-31-2016, 02:32 PM
Hey Matt, yeah it's hard to see in the images. It's loose, but not broken off. If you look at the basket finger in the top center of the photos you can see in one photo it hangs over the pressure plate, and in the other photo it doesn't. This may be how they are though, but I think this is the problem. I hope to do some testing later today. :P

In other news when I was making up the newest harness adaptor to power the MetraKit tach, and the Koso H2O gauge I decided to test out the Chinese EGT. I connected it to the 12 volt moto battery and poof smoke--the magic was released. :eek:

The little component next to the power connector fried.



06-01-2016, 03:39 AM
Well the cats selling the temp gauge are going to refund me. ;)

The next issue was the air box coupler. The new unit for the bike had the coupler for the 125 since I bought the 125 air box. But it seems to have split probably due to me not getting it placed properly on the carb. Things didn't quite fit and I had to make a slight mod to the coupler, which probably didn't help either. I got a piece of radiator hose, trimmed the coupler to fit and used tire patching rubber cement. Hopefully it will hold. If it does it will probably work even better than before because I was able to increase the length the tiny bit that was needed.




06-01-2016, 04:02 AM
Wow this is so cool. Anyone that's fitted a larger carb to a Derbi engine knows the pain of the trans oil filer cap/plug. Voca, the makers of the very nice pipes, has a really nice solution (http://vocaracing.com/product-category/cnc-accessories/oilscrew/). Heck I think I need at least a half dozen of these! CNC anodized aluminum. It comes in red or black. And they make them for the AM6 too. ;)

http://vocaracing.com/wp-content/uploads/2015/12/VCR-SD9188RE-VOCA-RACING-1-560x373.jpg (http://vocaracing.com/product-category/cnc-accessories/oilscrew/)

Of course if you get one of those you'll have to get the matching auto luber block off plate (http://vocaracing.com/product/oilpump-cover-voca-style-universal-mopeds-minarelli-am6-derbi-red/). :lol:

http://vocaracing.com/wp-content/uploads/2015/12/VCR-SD70000RE-VOCA-RACING-1-560x373.jpg (http://vocaracing.com/product/oilpump-cover-voca-style-universal-mopeds-minarelli-am6-derbi-red/)

06-01-2016, 10:43 PM
Today was another wisdom day--wisdom is what you get when you don't get what you want. :/

I started out with the exhaust issue. I though well maybe that's causing the vibrations. It most certainly was making a mess and loud volume!

The Copper sealer I had totally dried out so I had to get a replacement. I bought a can version this time. I think I like this style way better, and the prices was about half too.


Here are the suspects. There is suppose to be a Viton O-ring used with this manifold. When I bought the pipe from Treats they lost it somewhere between the time they took the web photo, and me buying the pipe. I've never been able to find the proper O-ring for this pipe, and as you can see the wrong ones don't last.




The plan was to slather up these parts with copper sealer, and that's just what I did. This seems to be working quite well, so that's good for now. I really really really want to get the Voca pipe on this bike. It's depressing not being able to Voca!




Here's how the oil plug makes unhappy with the PWK. I modified it today, but you'll have to wait for a photo of that mod as I forgot to take one today!


And it would seem that I might still have a drain plug leak. Have to keep an eye on this one--probably have to source a new crush washer.


This one surprised me a little bit. I'm bottoming out the suspension! The rear wheel is making contact with the subframe. I tightened up the pre a bit on the spring. This is a stiffer spring than comes with these shocks since I'm a lot heavier than the little ruggers that employ this shock on the Cobras. Even still I don't think it's going to be enough so I may yet have to source another spring. <sigh>


The big discovery today was this little issue. Seems that I didn't get enough torque on the crank shaft sprocket. This is held on with a taper fit, and I believe this was the source of the vibrations. I reset it, but I'm thinking that I got the balancer off. So now I've got to go back in there again. <sigh>


06-02-2016, 01:22 PM

06-02-2016, 07:33 PM
FYI, I have had luck in the past picking up Viton O-rings from Bearing Agency

06-02-2016, 08:09 PM
The other day GL and I went on a test ride. That's when the vibrations from the pinion gear started. I also noted the torn air box coupler, but I also noticed a dribble from the radiator. A new one is along the lines of 125€ plus shipping, and it wouldn't get here in time even if I ordered one today. I did some research and it turns out they make these zinc rods for brazing aluminum with just a propane torch. Well that's something I can due. About four bucks at HomeDepot--and I got the last one they had in stock. :happy:

I also picked up some spare propane (don't want to run out when midstream on a project like this one), a brass brush, some flux, and flux brushes. I wanted to get a brass wire wheel but they didn't have any. You don't want to clean the aluminum with steal because it will leave steal particles in the aluminum making it much harder to braze. :eek: