At 8700+ miles I did a routine inspection of the drive pulley when replacing my worn rear tire. I discovered the pulley retaining nut and pulley to be loose and the nut was held in place from backing off by the crush retaining washer. There was an abundance of rusty residue which is METAL FATIGUE and the pulley belt was riding on the outside edge of the drive pulley. The inner surface of the drive pulley still had the factory paint. Based on this initial inspection I took the following worn parts to my dealer: DRIVE PULLEY, COLLAR-SPACER (behind pulley), NUT & CRUSH WASHER and requested warranty replacement. My bike is not yet one year old! The dealer was agreeable to let me do the warranty repair myself since the bike was on my lift to mount a new tire. I had to wait two weeks for the collar because it was on national back order. IMHO it is imperative to replace this collar. When the pulley loosens up the preload between the middle shaft bearing inner race and the pulley is lost and the related parts begin to spin on the shaft and cause wear as well as the splines wash out eventually, etc. In my case the middle shaft was worn more then the drive pulley but I didn't recognize it at first!
When it came time to do the repair I found upon further investigation that the middle shaft was no good. I also replaced the middle shaft and small thin O-Ring between the bearing and collar that seal fluid from the transfer case. This seal has been forgotten by many a service tech during the recall process! I paid out of pocket for the middle shaft, o-ring & gasket but it's not worth wasting words over. I didn't trust the dealer's tech to do the proper repair and as such performed the replacement myself. IMHO the factory torque of 72ft/lbs was not enough force to tighten the pulley properly because of the design of the original retaining washer. The replacement washer is a different mat'l and design. I fabricated a special spanner tool to properly torque the pulley nut without using the brakes. There is no harm in over-torquing since the pressure is being applied between the inner bearing race only and pulley. The other end of the middle shaft floats in a bearing in the transfer case. I progressively torqued the nut to 125ft/lbs without any problem. The output shaft of the transmission uses the same nut and crush washer. This nut was not loose during the rebuild. I also replaced its washer and increased the torque value to 90ft/lbs just to be safe! Neither of these nuts are adjusting preload like front wheel auto tapered bearings. Currently my drive belt is running down the center of the drive pulley after 80 miles!
I agree with you and others that Yamaha has a real problem with their current drive pulley design. The thread, nut & spline are not generous for this final drive. There should be a recall..LOL.
I never perceived any stretching during the torquing process of the drive pulley retaining nut from 72-125ft/lbs. I'm totally confident with my repair procedure and parts replacement. I'm not confident that the repair will last because of the deficiency of the current design. The proof is in the pudding and only time will tell.
Some jpegs of failed middle shaft, tool & transfer case.
Image Insert:
Image Insert:
Image Insert: