I picked up a completely unrestored (and mostly unmaintaned, but low-mileage) 1978 750F a few months back. Last weekend I adjusted the chain, and while I was at it had the rear wheel off to clean it up some. Not sure if it was my fault, but one of the bearings completely came apart on my riding to work yesterday. Assuming I'd mucked up the chain setup somehow, I fussed with that for hours last night. Finally I took the axle shaft out again, with unusual difficulty, to find a bunch loose balls and sheet metal where the right bearing used to be. Glad I found this thread today, because I wasn't sure how to start... I may be back with pics and questions!