mystery vibrations...

[ABonenine]

I need some help. I have had my bike for a about a year(150sx) and for an unmeasurable amount of time it has been vibrating kind of violently when the revs climb at idol and when riding it. I only noticed it after riding my buddy bike of the same model and year. I completely pulled out the engine and re torqued the engine mounts so I don't think it's that and ive checked all other nuts for looseness. I'm stumped on why it would do this. Anyone have any advice?

i know that two strokes vibrate but this is not the normal vibration, i have been on the exact same model and year and it didnt do it...

[crf 250x]

Check every bolt and bushing.

[Tomok]

Check pipe mounts and o-rings.

[caharker17]

This is a bad option to have, but you might have twisted a crank. Not sure if anyone has done this on KTM's but on trials bikes, it is very possible. It gives a bad vibration and a lesser performing engine.

[JoeMcLaughlin]

This is a bad option to have, but you might have twisted a crank. Not sure if anyone has done this on KTM's but on trials bikes, it is very possible. It gives a bad vibration and a lesser performing engine.

I was thinking a crank issue as well. Also, check the flywheel. If you have the time you could split the cases, pull the crank, and send it to Andrew. He does fine honest work: http://www.cookseycrank.com/

Joe........

[SkiDaddy]

Check the head stays.

[tye1138]

If the left side engine casing seal is damaged somehow, it will allow water to get in. That water will eventually rust the flywheel and the rivets in the flywheel. I've had 2 flywheels go toast on me from rusty rivets and it causes quite the vibration when it happens.

Otherwise, I like the idea of a crank that's unbalanced itself. Its for sure rare, but it can for sure happen. If the motor is anywhere near the hour for re-build, I would pull it apart and send the crank to Andrew and take a real hard look at that flywheel.

[Rip Wheeler]

I'm guessing a twisted crank. Send it out to Andrew at Cooksey Crank and he will square it back up.

[KTM-548cc]

funny no one mentioned worn bearings. very common cause of extra vibration. usually the bearings at the crank because it spins fast but the one on the tranny shaft can make things shake also