Forum bmwbike.com

Problem: R27 with 10,000 miles on it. During a ride of about 30 miles or so, doing
30-45 in 3rd gear, I noticed for the first time I can recall a slipping of the clutch
when I increased the throttle suddenly. If I remained at constant throttle, no problem.
When I returned home, I noticed new clunking (metal on metal sound). At first I thought
it sounded like the center stand vibrating against the muffler, but that was not it.
I could generally make it stop by pulling up on the kick start lever or by increasing
the idle speed.

Any thoughts on the possible cause of this?

Hi Bob,

Long distance diagnoses are difficult and often very wrong as one has to rely on subjective opinions and impressions. You say that you felt as if the clunking sound came from the center stand. I assume that if it came from the gearbox, you would say so. Is my impression from your description correct that the clunking appears during motion? If so, it sound like a transmission related problem.

I reckon that you can fathom out the slipping clutch yourself. I'd like to comment on the possible causes of the clunking.
Hardy disk: Check to see if the hardy disk (26 11 3 038 476) is in good condition, and if the 4 hard rubber spacer rings (26 11 3 038 184) are still there. If the hardy disk has dissintergrated, then the steel locating lugs from the coupling from gearbox and drive shaft will make direct contact. If the hardy disk is ok, but the spacer rings are missing, or one or two are missing, the hardy disk with its protection ring will wonder around on the location lugs and foul on both the aluminium protection cover and the pivot for the clutch lever on the rear gearbox cover.

Coupling Hub: The coupling hub (33 12 3 038 146) should always have ample grease in it. They are often bone dry causing the splines to wear down (excessive play, thus clunking) and eventually they break away causing the drive shaft to turn freely.

After 10'000 miles, I'd like to think that the clunking is caused by one of the 2 suggestions above, and not by the bevel gears.

Best regards,

Mark
Mark Huggett GmbH