i have an 87 250 quadracer that vibrates horribly, when i bought it, the place that did the engine rebuilding, bored it .060 over and put a .040 over piston in it, since then i got the right piston, but it didn't fix the problem, I'm thinking the crank isn't balanced or it's not running true, can anyone help me on this.

 

Most likely you sheared the key on your counterbalancer. Did that many of times on my old lt. That is why I got rid of it. Hope this helps. Chuck

 

The first thing i would do would be to take off the clutch cover,and make sure the counterbalancer gear is properly lined with the main gear thats on the crank. there is a mark on the counterbalancer gear and on the main gear that should line up,it may be off,or the little key the other guy was talking about could have broken off. What are you comparing the vibration too anyways,the quadracers already vibrate enough to rattle every bolt out of it that doesnt have loctite on it. My friend rides a banshee and when he rode my lt250 he thought there was something wrong because of the vibration.

 

i've seen other quadracers and they didn't rattle have as much as mine, and everyone i asked told me it could be the counterbalancer, could it be off a different year maybe, and it vibrates so much it turns both of the preload nuts loose on the rear shock even when you use a pipe wrench to tighten them, even my cousin's dad who knows a good bit about 2 strokes from working on them said it could be the counterbalancer, so i'll have to tear it down and check it out