Cause I have '83 R100CS parts bike with what looks like an o.k. rear drive. And looks as if my R90's is leaking more and more.
Figured if poss. to just swap with out much trouble, then I can address the leaky one at my leisure, and still be riding.
Guess the axel is probably different size off the top of my head, but haven't had a chance to check. Probably some reason too, that can't just swap out whole rear end, drive shaft, swing arm and diff. I'm betting.