First post, I hope it is a good one. I just bought a 2006 Bruin 350 4x4 that has a bad knocking noise coming from the internal clutch area. I have pulled the primary clutch and inspected it. There are some issues in there that I will need to address, but that is for later. I re-installed the primary cage without re-installing the sheaves to help isolate the noise. It is still there. It knocks/rattles at idle but goes away on engine acceleration as soon as the wet clutch output shaft starts to turn. It returns as soon as the engine returns to idle and the shaft stops. There is some up and down and in and out play in the shaft, but I don't know if that is normal. I have a video but I can't post yet.

 

This may be just a difference in terms but I think all Bruins were CVT so had a centrifugal clutch and a belt drive variator, so only one clutch. I did have a Grizzly with a similar fault and it turned out to be the rivets on the clutch drum loose. It would seem to be the centrifugal clutch if the noise goes away when it is engaged.

 

Yes, it is the centrifugal clutch at is inside the crankcase I am referring to. It rattles at low idle, as if it is trying to engage. As soon as the RPM increases and the shaft starts to turn, the knock goes away. As the engine returns to idle, it knocks just as the shaft comes to a stop. I haven't had the time to pull the wet clutch out and inspect.