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View Full Version : About to be new to the RS250 fold



soofle616
03-05-2010, 03:35 PM
Hey all,

I am very hopefully going to be adding an RS250 to my stable right between my Mille and RS50 and was hoping you guys could give me some pointers. 1st, I am still very new to 2 stokes, the 50 being my only experience with them outside of a chainsaw. 2nd Since I can't seem to find an owners or shop manual for the 250 (i have searched here but haven't found anything that I can actually use), everything I know of it comes from skimming through posts in this section. So here are my questions:

1) skool me on multi cylinder 2 strokes in as much as they are different from single cylinder

2) what the hell is an exhaust valve and why do I keep seeing posts about it as I go through this section?

3) what are the common problems this thing sees, and how bad do those common problems get? (Example: the mille suffers from tank warpage on certain years that have plastic fuel tanks which leads to fuel leakage)

4) since I haven't pick up the bike yet, what specifically should I look for when I go see it? I have been riding for 10 years and have gone through my share of used bikes but this is a new animal to me so outside of the usual list of is it damaged at all, does it start, does it run, what does it need, etc., etc. where do i look for potential problems.

5) other than tyga and af1, where do I look for replacement or upgrade parts?

I'm sure all of these questions have been answered but my searching has not gotten me very far. All I really need is to be pointed in the right direction for older threads and I can do the reading on my own so you all don't have to rewrite everything. Thanks a bunch, looking forward to Ape number 3 :cheers:

R1Frank
03-05-2010, 04:12 PM
Do a lot of homework and learn as much as you can about them before you buy, because you will probably be doing your own maintenance. Detailed shop manuals can be found, but it takes some searching. Then buy a really well-maintained one from a seller you think you can trust. If you get a worn out bike that's ready to grenade, you'll curse it like a bad case of the clap!

soofle616
03-05-2010, 04:35 PM
Do a lot of homework and learn as much as you can about them before you buy, because you will probably be doing your own maintenance. Detailed shop manuals can be found, but it takes some searching. Then buy a really well-maintained one from a seller you think you can trust. If you get a worn out bike that's ready to grenade, you'll curse it like a bad case of the clap!

Doing my own maintenance is a given. I do all my own work except when it comes to things that require specialty equipment outside my budget (can't re-plate cylinders just yet). This is why I have been trying to find a workshop manual, first so I have it and have a proper reference to go to but second so I can flip through and get an idea of what's different about this bike compared to what I already know from my other bikes and start learning how things go together.

Regarding the worn out bike that's ready to grenade, that's a chance everyone takes when buying used. Unfortunately (or fortunately depending on your point of view) these things aren't exactly a dime a dozen so holding out for a couple weeks and checking out the fresh crop that's up for grabs isn't so good an option. And the area I'm in means that anything that does come up is going to be at best, a long ass drive away and at worst, beyond my ability to see in person prior to buying.

agabinet
03-05-2010, 05:38 PM
Exhaust valves . . . or power valves, more properly, are essentially a means of lowering and raising the top of the exhaust port to increase engine efficiency. At low rpms you can lose unburnt charge out the exhaust port, so a powervalve is designed to minimize this by lowering and raising the port at different RPMs. Different two strokes have different types of powervalves. The RS250 has a setup with two valves per cylinder, attached in a housing at the exhaust side of the cylinder. Each valve is a modified cylinder itself, and each modified cylinder is really three slices held together at the back. The middle slice has a pin that inserts in slots on the other two piecs, and it can slide back and forth. A pulley, actuated by two cables, in turn operated electronically by a digital controller, causes the different slices to be pulled away from the exhaust port at rpms above some set number (probably in the 8ks). The slice that previously blocked part of the exhaust port is now pulled up and back, effectively enlarging the exhaust port as RPMs rise and the risk of unburnt mixture excaping is reduced, in part by the returning pressure wave from the exhaust pipes that is tuned to work at the most effective rpm range. If you don't know how two stroke exhausts (expansion chambers) work, search the web for a nice explanation by Eric Gorr, or one of the other techie articles that are out there.

Aside from the usual stuff (knackered head bearings from wheelies, rusty tanks, rash from the bike going down, safety wire holes, etc.) the one thing that's known about this bike is that if the chain is not kept sufficiently slack, it can put so much tension on the cradle that the cradle actually cracks in front where the motor mounting bolt goes through the cradle. Look for cracks or welds. When I bought mine, I discovered massive welding beads up front on the cradle, and I knew what had happened!

Two cylinder two strokes are just like singles -- but twice as much fun.

agabinet
03-05-2010, 05:40 PM
Oh, and The Tuning Works in the UK, run by the RGV250 forum moderator, sell lots of great parts.

soofle616
03-05-2010, 06:05 PM
Exhaust valves . . . or power valves, more properly, are essentially a means of lowering and raising the top of the exhaust port to increase engine efficiency. At low rpms you can lose unburnt charge out the exhaust port, so a powervalve is designed to minimize this by lowering and raising the port at different RPMs. Different two strokes have different types of powervalves. The RS250 has a setup with two valves per cylinder, attached in a housing at the exhaust side of the cylinder. Each valve is a modified cylinder itself, and each modified cylinder is really three slices held together at the back. The middle slice has a pin that inserts in slots on the other two piecs, and it can slide back and forth. A pulley, actuated by two cables, in turn operated electronically by a digital controller, causes the different slices to be pulled away from the exhaust port at rpms above some set number (probably in the 8ks). The slice that previously blocked part of the exhaust port is now pulled up and back, effectively enlarging the exhaust port as RPMs rise and the risk of unburnt mixture excaping is reduced, in part by the returning pressure wave from the exhaust pipes that is tuned to work at the most effective rpm range. If you don't know how two stroke exhausts (expansion chambers) work, search the web for a nice explanation by Eric Gorr, or one of the other techie articles that are out there.

Aside from the usual stuff (knackered head bearings from wheelies, rusty tanks, rash from the bike going down, safety wire holes, etc.) the one thing that's known about this bike is that if the chain is not kept sufficiently slack, it can put so much tension on the cradle that the cradle actually cracks in front where the motor mounting bolt goes through the cradle. Look for cracks or welds. When I bought mine, I discovered massive welding beads up front on the cradle, and I knew what had happened!

Two cylinder two strokes are just like singles -- but twice as much fun.

Thank you for the explanation on the power valves. I did learn about expansion chambers when I got the 50 but I clearly have a lot more to learn about 2 stroke tech in general.

As for the cradle thing, that's exactly the kind of thing I need to know, thanks!

crudmop
03-06-2010, 10:06 AM
Another northeaster, welcome to the team :) Will you be attempting to street it?

agabinet
03-06-2010, 02:20 PM
Another northeaster, welcome to the team :) Will you be attempting to street it?

If you boys come to New Jersey Motorsports Park with your bikes to ride the track, let me know, we'll have a stinkbike brigade. Mine is for the track, although I have all the street gear.

soofle616
03-06-2010, 03:26 PM
Another northeaster, welcome to the team :) Will you be attempting to street it?


If you boys come to New Jersey Motorsports Park with your bikes to ride the track, let me know, we'll have a stinkbike brigade. Mine is for the track, although I have all the street gear.

Actually I have to update my profile. I was a northeasterner until about a month ago. Im on the other coast now :rolleyes: well almost.

Inunf
03-06-2010, 04:55 PM
1) It's safe to see the RS 250 as two 125 cc singles that just happens to be connected to the same crankshaft. For instance, the carbs has different size jets as standard.

2) The reason for all the posts is that the PVs are a weak spot. Unless you upgrade them or maintain them very well, they might brake and take the piston and barrel with them.

3) The above and the cradle as mentioned. Otherwise they're pretty good for being a two stroke. Do the required maintenance though, otherwise it'll disintegrate when you least expect it.

4) You might notice that the back pressure from the pipes is different, and that one pipe smokes more than the other on idle - that's normal. It should have some midrange, but not very much, and a healthy kick around 8,5 krpm. Check that the gears are in order. Ask for receipts for rebuilds, or expect that they haven't been done. Factor in the cost of a rebuild if there are no receipts.

5) www.thetuningworks.co.uk - great service and a lot of nice stuff. I've spent loads there and can absolutely recommend it.

Service manual (it's in English as well):
http://www.solo2tempi.it/manutenzione/stradali/manutenzione%20rs250/manuale%20officina/manuale%20officina.htm

Buying advice (this is for the RGV, but the engine is the same):
http://www.rgv250.co.uk/buyingadvice.htm

You might want to browse around that site, loads of good info there. Also the forum is great, a lot of people in the know there.