I have a 86 250R with alot of porting. I have the jetting down too near perfect. The engine runs fantastic but falls at the 7/8 to W.O.T.
I'm running a stock carb with ESR K&N filter, ESR TRX 11 pipe and silencer. Stock ignition. The carb jetts are 48 Pilot 72 Main. I'm currently about 200' ASL. The spark plug gap has been reduced to 0.024 to help compensate for the higher compression. I need some ideas from tunners.
Q. Will the stock ignition limit my top end and can I compensate with closer plug gap?
Q. Will the Stock Keihin PJ limit the air flow at the top? and what size carb would fix this problem if you think this is the problem.

Need help soon I have some Bashee's too race.

 

Yes, the plug gap should be reduced to about .020 because the stock 250R ignition is pretty weak. The stock PJ will also limit the air flow, and not supply enough if the cylinder is ported that much. Also are you running stock reeds? Do you have the reed stops on them. If they are on there I would try taking them off and see what kind of a diffrence that makes.... The carb i would choose for all around riding would be the 36mm A/S keihen carb.

 

Dragracer thanks for confirming my thoughs. The reed block has a reed spacer with carbon fiber reeds (New). The plug is gapped @ .020 as of today. Made a couple of passes with no change. I will try a couple more with the air filter off. That should confirm lack of flow. What do you think about the 38mm Air striker?

Glenn

 

The 38mm A/S carb is what I have on one of my 250R's. Its a great carb. It runs smooth and is real easy to get tunned in. With your cylinder being ported you would notice a huge diffrence in power! Now, be careful when you run that bike with out an air filter. Make sure theres no dust or other types of particles that can get sucked in.

 

Well I made (2) Passes on the street with out the air filter. The bike ran great. Will order new 38mm on Monday. Thanks for the response. Forums like these saves money.
Glenn