Need 250 Carbs - Also, Stan Stephens 300cc Mod Report

[RisAllen]

Greetings from NC.
Does anyone have an extra pair of stock RS 250 carbs for sale? I had mine bored by MotoTek (from 34mm to 35.5mm) at the same time that the motor was modified by Stan Stephens (www.stanstephens.com/rgv.htm) to 300cc. Ever since, the bike has not run as strong as it did when it was a stock 250 (Arrow chambers and holes in air box). After spending a lot of time trying umpteen different jetting combinations at the track - none of which yielded good power - I suspect the problem may lie with the bored carbs.
In the process of trying to get this thing to run correctly I managed to ruin a piston. Mr. Stephens has a proprietary setup with Wiseco so I had to purchase the replacement from him. All I can say is he thinks very highly of his pistons...hold on to your wallet! The price is out of line, especially considering the nature of a two stroke and their need for new pistons from time to time.
If I can find some stock carbs and they make this bike run right, then all will be well until rebuild time. At that point, or if the carbs don't fix the problem, then I will probably abandon the 300cc motor as a failed experiment and look for a stock motor to purchase.
Oh....if only I had my strong running, dependable original 250 back again!

[webbo]

Read you’re comments with some interest as I had been considering a few adjustments to my RS250.

The bike handles and brakes superbly but I do fancy just a bit more horsepower, just to really stick it up the 4 stroke know it all’s.

I had been looking at the 300cc rebore but if it causes the kind of problems you list, I don't think I want the agro.

I already have Tyga pipes, uprated clutch springs and less teeth on the front sprocket (This has given me better acceleration but top speed of 115mph) but I still struggle with 600cc 4 strokes biting at me on the straights. I don't mind this so much but it's a bit predictable when they pass me on the long straights just for me to go back under them on the bends.

I would like to be able to put a bit more distance between us when accelerating out of the bends.

If you were going to chase more BHP again which route would you go?

[neil coles]

Can only say that I have been running the SS 300cc conversion now for 6yrs (track days) and only had 1 problem which was not related to the conversion (water got onto crank shaft causing bearing failure). I am running standard carbs and jetting and the engine runs and sounds sweet, slightly more vibration than a standard one though but this doesn't seem to be a problem. I have tried messing with carbs and jets but the standard set up seems to suit it best. I can't be bothered to experiment myself, the bike has been dyno'd with a healthy 69-71hp.
I bought replacement wiseco pistons for this conversion direct, can't remember who they were but will try to find number. These pistons last ages had my current ones in for 2 full track day seasons so far, just put knew rings on and the pistons still look good.
The conversion isnt cheap but I lost a standard piston (crown went) and it damaged the barrell so I thought I might as well do it.

Webbo - try going faster round the corners that way 600's won't catch you so quickly! you won't compete in a straight line with 600's, not from low speed with the RGV engine.....maybe a Honda!

[999]

RisAllen- Just wanted to say hi. I think I sold you my 900CR (Melbourne, FL) about 4 years ago! Hope you get your 300 straightened out. Maybe the guys at AF1 can help?

[$hithead]

I have stock carbs from a 1999 Aprilia RS 250 "Cup series" bike. $100 for the pair plus shipping. Email me: Duc995@aol.com

-Rob