Maintenance & Technical > KX250 / KX125

91` 125 wont rev

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Jopiz:
I have struggled with the problem for about a week. The problem is that my bike wont rev to higher RPMs than 6000. It just sputters and loses power instantly. Pulls pretty strong below 6000 RPM. Jetting is fine. I have tested compression and got 167 psi. I replaced the ignition coil and it runs a little bit better. It fouls a plug in 5 minutes. Smokes alot and spits oil/fuel mixture through exhaust. It doesnt lose any transmission fluid so wet side main seal isnt leaking. Carb is OK and reeds are tight. It simply feels like it has an RPM limiter at 6000 RPM. Stator, flywheel, igniter, pulse coil and ignition coil has been tested and verified to be operating fine. Starts first kick without choke. I can even start it with my hand but still it has lots of compression. The crankcase hasnt been pulled apart. Im sure it doesnt leak.

Any thoughts what could cause my problems?  :mrgreen:

Jopiz:
Can KIPS cause my problems? If it is stuck or somehow not moving so it blocks the exhaust ( KIPS in in normal closed position). I had to replace the rod that operates KIPS because it was bent and the threads were damaged. If i lock the KIPS fully opened does it start? I know it will lose loads of low end.

-Jopizz

BullKaw:
What brand of tach are you using? What is the max rpm suposed to be?

Jopiz:
Im using KOSO ATV meter for speed, temperature and tacho. Its very reliable. Im not sure about the exact max RPM. But i know its well past 10k.

pickledkiwi:
Lock your KIPS open or disconnect it. Doesn't matter too much. Do what ever is easiest. If you get more rpm with it locked open then it wasn't opening properly in the first place. If you disconnect it and get no rpm change at all then it wasn't working in the first place!

Might pay to check your muffler first. The center tube may have collapsed and is restricting gas flow at higher rpm.

PK

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