Forum bmwbike.com

I went on the first major ride of the season, and after 50 miles or so, it felt like the clutch suddenly engaged; I had no forward power, but the motor was still running. I thought maybe I cooked 4th gear, so I downshifted into 3rd. Still nothing. Coasted to a stop. Gearshift clicks into all gears, and when I pull the clutch, I feel the resistance of the spring. I loosened the bolts at the clutch arm on the back of the transmission, so that the clutch would have the maximum pressure on the flyweek, but only the barest minimum of resistance was felt when I had the bike in gear, and turned the rear wheel by hand. Any ideas?

Dear Jon,
I had exactly the same symptom on my R50 some years ago but thankfully only 100 yards from home. I discovered the clutch friction plate hub had sheered its rivets. The only solution was to replace it.I have also seen friction plates with loose rivets. If you think, all the engine torque is transmitted through those rivets, so if they loosen up for any reason (old age most likely)they will soon wear through.
Gerry

Sounds like your clutch and transmission are working but disconnected from the wheel. Undo the front clamp on the rubber boot behind the transmission, and see if perhaps all the screws have backed out the flange of the universal joint.