It happens in all forward gears. The quad seems to shift and it does not feel like slipping. I makes a loud bark when you first get on the throttle. I think it could be coming from the rear, but not sure. I certainly sounds like something is breaking and going to let go soon. How can I narrow this down? Any common issues? Thoughts? Thanks.

 

We had one in as a trade in, that had a worn LH rear wheel bearing. The Boss lent it out as a courtesy bike, and the splines on the axle went inside the diff. Crownwheel splines were badly worn too, so ended up with new axle shaft and crownwheel. Was able to get a "non genuine" axle, always a sign of a common problem. Many Yamahas use a similar set up at the rear, and their axles let go if the axle bearing is not changed as soon as it gets play in it.

 

Turns out that it is related to the rear brakes. My son and brother in law adjusted the rear brakes. When we loosened the brakes back up, the sound goes away. It seems when the quad squats from a hard acceleration, the brakes bark loudly. If I loosen the brake back up, the sound completely disappears. Ideas?

 

Could be badly routed cables, the outers can pull out of the backplate as the swinging arm moves if the cables are not routed right, or the wrong cables fitted. However, back to wheel bearings, if the axle and drum are moving about due to worn bearings, you can get that brake chattering effect. Jack the bike up on the tow bracket, slacken brakes off and see if there is any movement in axle bearings either side. May be worth taking back brakes apart, cleaning them, de-glazing shoes and drum surfaces with emery etc. May be easier to check bearings with drum off too. Don't over adjust back brakes either, as long as the parking brake holds the bike, it is tight enough, and the footbrake is OK if the pedal doesn't touch the footboard when pressed hard.