[316hepster]

Got a 10 crf250r for my son. At wot it was bogging really bad. I took the tank/pump from my 09 450 and put it on the 250. Started and ran like a charm. So I assumed fuel filter kit was the fix. Kit came in and I put it on. Bike still running bad at wot. So I bought a used pump off ebay. I put the new filter kit on and put it on the bike. Still runs crappy. Even worse than before. So for kicks and giggles I put the "bad" fuel tank/pump on my 450 and it ran like it's supposed to. I put my 450 tank/pump on the 250 and it still runs like crap. What did I do to mess up the 250??? Obviously not the pump at this point... It starts occasionally and runs for a few seconds.

Spent another 2 hrs cleaning throttle body and its parts. Started for 5 sec and kaput!!!

[JimDirt]

Its possible that the CDI is going bad , but usually when they go bad , the bike wont run or will hardly run at all at any RPM , i would also check the coil and stator output , make sure they are functioning properly , , my first guess would be the coil breaking down