Ok ill try to explain this as best as possible. When u remove the side plastic then remove that "cage" around the clutch then theres that big bolt that holds the clutch in place and i assume makes it engage when u accelerate, keeps coming off. Even when we put the grown man tightening on it. Anyone have any suggestions?

 

Hey!...thats something that has never screwed up on mine...lol.. I would try a new nut and a 1/2" air impact(take mine off twice a year and no problems yet nearly impossible to hold and tighten by hand). The big nut just holds the sheave assembly in place(pretty much no other function...yet an important one...lol) Make sure the big washer is still behind the nut. My Service manual says should be tightened to 72 ft. lbs. (seems a little light to me).. a couple drops of lock-tite can never hurt!

Yamaha Part #'s
primary sheave...
Nut - 90179-16001
Washer, plate - 90201-190t7

Hope I was helpful, Good luck and happy wheelin!

 

and i almost forgot...if u do not have the tools to decompress the secondary sheave... when u tighten the nut on the primary sheave ..make sure the splines on the outer plate line up...tighten a little...rotate the sheaves by hand a couple of times ...then tighten a little ...then rotate the sheaves a couple of times...otherwise u will tighten the front sheave against the belt and not against metal as is should b and will already be loose when u start the wheeler.....i just put a new belt on mine last night..and it reminded me of that... once again... best of luck to ya!