'00 SR50 Minerelli Kit and pipe has me at wits end - ANY HELP?

[AllstonEP]

I have been working on a 2000 SR50 for many months now and just can't figure out why it wont rev out and run better than original. I am a relatively knowledgeable mechanic and have even written an article for putting a kit on a LX50 on ModernVespa.com.

Back story - it took me many weeks/month to get the right parts from Germany. They sent 2 Morini barrels (70cc) and Morini exhaust, before I got the right parts for a Minerelli. The kit is a Motor sport kit (70cc), looks generic/not polini or molossi. That is what Scooter Center Germany offered up.

So at this point it is all together. On the center stand it revs out great! But under load, it is boggy and hardly runs well. I almost have to choke it to keep it running.

I have changed rollers to 3 different sizes. I checked the belt to be the right size, still using stock belt (may be problem). I have ridden the scooter for 10-20 miles and ran it for additional hours, so I think it is broken it at this point. Enough where it should have power off the line. Another weird thing is the power bands are crazy curves. A few spots were it does start to have power. Finally, it I am going down a hill and it can rev up, the power really does kick in.

What I am thinking it could be at this point:

1. Carb - Maybe I need to upjet more, I upjetted a bit. But I wouldnt think it would rev on center stand if jetting was off and the spark plug color is nice. Or maybe carb is dirty or flow/float issue.

2. Belt - maybe the belt is slipping, too much power for stock belt????

3. Leo Vinci Exhaust - maybe there is something wrong with the exhaust. I have not tried putting stock exhaust back on yet. I did cut the restrictor out.

4. Is there anything weird with the CDI or a computer control?

The customer has been really patient with me and this horrible project which should be an easy bolt on, gas and go. But we are both very frustrated and angry at this point.

Thanks for any knowledgeable help and hopefully someone has experince with this.

Eric

[Snugg]

Welcome to the forum Eric, I can relate to your frustration.

At this point it could be a few things.

A little more info would greatly help the troubleshooting.

Stock carb? jet size, needle position? Air filter stock?
Stock variator? What weight rollers did you use? Are you sure their the proper size?
Shouldn't be your belt. At this point, you're probably only pushing 6-7 hp. The stock Aprilia belts are pretty good and have no issues with that range of hp.

What is your cylinder compression at?

Clutch springs and contra?

[AllstonEP]

Stock carb and Air filter stock? - YES

jet size, needle position? - 75-78 jet with stock needle postion

Stock variator? YES

What weight rollers did you use? black Stock, blue 6.0 (or 5.0?) and green 4.2 (CAME WITH EXHAUST I THINK)

Are you sure they are the proper size? - WEIGHT - NOPE. SIZE - YEAH, I can tell dif/measure them, but blue ones were a bit crappy on the edges, so I rounded them. Shouldnt make a HUGE dif because black and green were good, so that would tell me at least it it can rev up under load.

BELT - YAMAHA STOCK. I matched it to an old one I had from same SR50 from another customer.

What is your cylinder compression at? - good 120

Clutch springs and contra? - Stock clutch springs and MAYBE I replaced Contra if it came with exhaust.

Rollers and maybe Contra came with kit or exhaust and I think usually that stuff comes with Leo Vinci exhausts.


THANKS MUCHO!!!

Eric

[Snugg]

I would start off by installing rollers that haven't been modified. Rollers with edges that are rounded have a tendency to rotate and bind. Also, if you mix rollers, I have always been taught and from personal experience, bogging under load can happen when you mix roller weight greater than 1g difference.

Contra spring problems arise during transition, so I think yours is good
Compression is good. Your low altitude helps with that! I'm a bit jealous.

Bogging under load typically means CVT tuning.
Bogging while on the stand and under load typically means carb tuning.
So honestly, I think the problem has something to do with the carb and-or CVT

I am not very good with carbs but I'll share something I found.
I'm at 5800 feet, usually with 70cc, stock carb and stock air box, most people around here run with an 82-85 main
Maybe at your lower altitude, since you have more air, you might maybe try a larger jet?

I could be wrong, and I'm happy to hear other people's opinion

There are some great people on this forum, I'm sure somebody else will reply soon. Until then, good luck!

[marky boy sr50r]

tryed playing with the mixture screw ??

[AllstonEP]

It does NOT bog on the center stand.

I did not mix roller weights and the black and green were perfectly made/useable.

I might be wrong about the jet I have in their, regardless it is stock jet (75 or 80?) or a few steps up. Again, spark plug looks fine when I do ride it. I never revved the hell out it long enough on the center stand to think it worthy to pull spark plug.

I could play with carb more, jets and mix screw, but my knowledge of mix screw is it affects how it throttles. And it throttles great on and off center stand. But maybe since I have to have choke on sometimes suggests a bigger main jet.

I know nothing about CVT tuning. If it came with springs, should I just change them or get a upgraded clutch?

[Snugg]

Clutch only effects RPM of engagement. You should install the clutch springs it came with. Exhaust usually come with new clutch springs, contra springs doesn't.

It's important to know where the power band of the pipe is and use the proper roller weight to match that power band. What is the part number to the pipe?

[AllstonEP]

It is the Leo Vince ZX

http://www.scooter-center.com/scoweb...&category2=CAT

[AllstonEP]

The kit was this (or like this) not sure what the "Piaggio" engine was.

http://www.scooter-center.com/scoweb...&category2=CAT

[Snugg]

Ok, to make it easier, next time you need to order parts, you should use HGT. http://www.highgaintuning.com/ He is local and can get you anything you want. Plus the orders won't be messed up! He also owns lots of SR50 including a 2000 carb Minerelli
With that exhaust, you want your WOT acceleration RPM to be set to 8,200 RPM. Clutch engagement around 5.5-6k RPM So match your rollers to that RPM and you will be perfect. Red LeoVince clutch springs and a malossi white contra. I don't know what Yamaha belt you used, I have worked on a crazy amount of both Aprilia and Yamaha and I haven't found a belt that is close enough to use. Proper way is to look up the tolerance for belt and use those measurments. Wrong size belt will throw everything off.

To tune the carb you will need to be more specific on where the power is lacking at what throttle position. If you can, take a video. Probably the best way to show.

[AllstonEP]

No idea what this means - "WOT acceleration RPM to be set to 8,200 RPM"

no video needed yet, this thing is way off, barely accelerates. Much worse than stock.

Will check springs and contra.

Will send picture of belt, again, I got 2 of them.

[Snugg]

WOT = Wide Open Throttle

When you tune roller weights, you tune them for WOT acceleration and you match them to the power band of the exhaust.

In your case, your exhaust produces the most horse power at 8,200 RPM. So you want to tune your CVT to reflect 8,200 RPM while accelerating at full throttle. If tuned correct, the RPM should jump and stay around that range throughout the entire transition of the pulleys. Then once complete transition has occured, the RPM will go up from there. If your RPM goes to that range but drops while accelerating, that means that your contra spring is too weak and allowing the rear pulley to open too soon.

If your roller weight are too heavy, it will bog and not acclerate under load.

If your roller weight are too light, it will over-rev and not produce enough power which also lowers your acceleration.

Once you get the CVT set up perfect and it still bogs or has acceleration problems, you will know for sure it's the carb settings.

[AllstonEP]

ooooohhh, I am liking that! Now we are getting somewhere. I was wondering why the curve on this things is as weird as a LX50 (4 stroke) go up and down hills. I got no revs no matter what rollers are in there. So let's look at the Conga.

I found this belt in two different SR50s, so I assume it is from the factory - both low mileage and unmolested.

[Snugg]

That belt is an OEM belt from an Aprilia 1997-2000 SR50 Carb. So you're good there!
Here is the link http://www.af1racing.com/store/Scripts/prodView.asp?idproduct=2611

[AllstonEP]

I got the yellow springs (NOT RED). Never installed them, should I or get the red ones.