Hey guys. Ihave a '89 Yamaha Exciter 570. My problem is my sled jerks or jumps on take off and then stops after i get going a decent speed. It still makes a small thumping noise and vibration on the clutch side. Jack shaft bearing? Both clutches look to be in good shape as far as i can see. The primary clutch is off of a newer Exciter I think '92 or'93. Does this have anything to do with it. The same jerking was there before i put on the newer model primary clutch. Any help is greatly appreciated!!!