3,000 RPM increase for no apparent reason

'04 CRF250X RPM's will suddenly increase by about 3,000 at idle or while riding when throttle is released. Throttle cables are lubed, clean and have POSITIVE return to closed position! Carb has been removed and had all orifices cleaned with carb cleaner and blown out with compressed air 3 TIMES! I re-jetted this carb while I had it out, but this problem was occuring beforehand! Pretty scary to release the throttle and have the RPM's increase while out riding. This occurs MANY times while riding, but NOT everytime! HELP!

I'm sure someone with more experience will chime in, but have you checked to make sure your float is working properly and set correctly? We had an ATV many years ago that did the same thing and it was a bad float causing intermittent flooding.


Can you be more specific.........."it was a bad float"? Float had a leak and didn't actually float? Float valve didn't function correctly? And how would you know that, since you can't see through the float bowl? How does one test for that condition?

Anyone else out there have a reason for this condition?

Can it, possibly, be a problem with the CDI unit?

this kind of thing can happen if you have an air leak at one of the carb boots.  check those carefully.  spray some carb cleaner around there and see if the idle speed changes.  if it does, you have an air leak.

this kind of thing can happen if you have an air leak at one of the carb boots.  check those carefully.  spray some carb cleaner around there and see if the idle speed changes.  if it does, you have an air leak.

Thanks............I forgot to mention that I had already done this..........several times!

I think your bike has a hot start.

On my 05 crf250r my hot start was sticking open.

I loosened off the cable and cleaned out the gunk that was built up where it accesses the carb.

Just a thought.

Sounds like a hanging idle to me, which is caused by a lean slow speed mixture.  Turn your fuel screw out to richen the slow speed circuit while adjusting the idle down with the idle screw.  If you never have to use the hot start lever to start when hot then this is most likely the problem.  Like filterx said, check that the hot start lever is not sticking first.  Then start adjusting the slow speed circuit.




~ DS

filterx and DeadSpider,


I'll check those things soon......might be able to get out tomorrow for a ride.


Thanks guys and thanks to my other responders!

Yeah man...

Hope ya get her out for a rip.

It look's like I'm a bit north of you. Weather is awesome and waiting for my bud to show up so I can rip the knobbies off my new maxxis :)

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