Ring Gear Separated from Flywheel

[wecm31]

Does anyone have a handle on the ring gear coming off the flywheel? My bike is a 1985 R80RT. Last spring I had an oil leak at the rear of the engine, tracked it down to the oil pump cover, changed that o-ring and the rear main seal as well. Everything bolted up fine, started my riding season. About 1000 miles later, I began to hear some metal to metal contact when shifting, followed 100 miles later by a horrible racket. A look through the timing cover and a poke with the finger confirmed the ring gear was off the flywheel (clutch carrier). Ended up having to push start the bike to get it started again. Once I made it home, stripped it down to the rear of the engine again. Everthing was found tight, the rivets had sheared off the flywheel and the ring gear was just riding on the flywheel. I borrowed a dial gauge and couldn't detect any end play of the crank, I had blocked it from the front when I removed the flywheel both before and after the failure. Can't help but ponder if I botched something when I changed the main seal and the oil pump cover. I had also installed a Nippondenso starter before the failure, did the higher torque rip it apart? I have ridden 2000 miles on the new flywheel, no issues. No one I have spoken to has ever heard of a ring gear separating from the flywheel.:confused:

[Voni]

We had one case of this at the Kansas Rally one year on an almost new bike, back about when your bike would have been new too. The guy was from Colorado about 600 miles from home. We pulled the transmission at the rally, under a shade tree, and just took the ring gear out of there so it wouldn't bang around and maybe lock something up on his way home. He was riding with another rider so they just bump started it going back to Colorado.

I doubt you did anything to cause it.

[wecm31]

Just got my July copy of Airhead in the mail last night and Oak has a piece on the same issue, rare but not unknown. Thanks to him and Voni for easing my concerns. One thing I still can't figure out......what caused the metal to metal noise prior to final failure? I just can't shake the idea of the crank floating forwards as I pulled the clutch to shift, thereby touching the semi detached? ring gear against the engine casing. Or was it just the deceleration during the shift causing it to flop forward a bit? Still riding, fingers crossed!!!