CRF250R high rpm cut out before rev limiter

I need some ideas on what might be happening with my bike.  I just did a full rebuild with a 13.7:1 je piston and I am running vp110 with a 180 main and moved the jet needle clip down one position.  The mid range runs like a raped ape, but at 10,000 rpm the bike hesitates and its almost like valve float or ignition problem?  It will not reach the limiter and has nearly caused me to wreck multiple times.  Please suggestions or anyone who has experienced the same problem! thanks brett


oh, and i thought the cam sprocket had spun but just rechecked timing last nigh and it was ok.. so now i'm stumped on what could cause this.

The cam sprockets do spin, and without dial gauge you can't confirm cam timing.

But it's probably running on too high of octane!

May sound simplistic but do you have new spark plug properly gap'd? I had a failing ignition coil that caused a hi rpm flutter. If I decreased the plug gap the bike would pull more rpm's. A new coil allowed for the proper gap w/o flutter.

I know in the past I've had a issue like that where it sounded like it was hitting the rev limiter low and it turned out being the main jet was too big

Exactly. If you a have octane that is too high, or a main that is too big, it will 'gurgle' at WOT, if the rpms are not high enough.

You're bike is most likely running too lean. Im not sure what causes that but a lean bike will do that and loose a lot of performance. You shouldn't need to rejet but just play with the air/fuel screw.

You're bike is most likely running too lean. Im not sure what causes that but a lean bike will do that and loose a lot of performance. You shouldn't need to rejet but just play with the air/fuel screw.

 

Air fuel screw is for idle only

 

A 180 main jet is way to big

 

Try a 165

Don't you think 165 will be a little small?

Don't you think 165 will be a little small?

Stock is 142

Uncorked is 155 reccomended

Port and polish and cam is 160-165 maybe 170 with full race ProCircuit pipe (extra short header)

 

VP 110 is not oxygenated, so you don't need to go so rich to compensate for the extra leaness of the fuel

Stock is 142

Uncorked is 155 reccomended

Port and polish and cam is 160-165 maybe 170 with full race ProCircuit pipe (extra short header)

 

VP 110 is not oxygenated, so you don't need to go so rich to compensate for the extra leaness of the fuel

oh sorry about that i thought stock is 172

The stock main jet is not 142. It's 170 for an '05. You're confusing it with the stock pilot jet size which is 42.

The stock main jet is not 142. It's 170 for an '05. You're confusing it with the stock pilot jet size which is 42.

 

No, I was thinking of the X, not the R sorry

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