Clutch slipping or not

[walterK75]

My 1991 K75 clutch seems to be slipping in second gear. When accelerating fast or slow in second gear I sometimes get a sudden increase in engine speed and then a bit of a jolt. I first experienced this going up a hill and sometimes accelerating out of a turn. It's kind of a kick in the pants and then engine speed settles down and I can continue riding normally. I sometimes get a couple of jolts close together. The transmission does not pop out of gear. I was told it's a worn clutch and that second gear is where a worn clutch first shows itself. I have not had this happen in other gears. I've tried to force it in third but it's rock solid and no jolts, so far.

Does this sound like a clutch or something more sinister? This just started. The bike has 66,000 kms and used to be a police bike.

[BuddingGeezer]

Police bikes are very hard on clutches. Sounds like the clutch to me.

Ralph Sims

[98lee]

First check the clutch adjustment. Easiest and cheapest.

Next look at the final drive/driveshaft splines. Remove rear wheel and a few bolts. No cost (if they're good). Bad splines could cause the symptom you describe.

Get back to us with the results.



:dance:dance:dance

[cjack]

Sounds like 2nd gear is popping out and back in to me.

[bikerfish1100]

agree with cjack, sounds much more descriptive of a transmission issue than a worn clutch. a slipping clutch is most likely to show up in the higher gears first, and then work it's way down to the lower gears. If clutch is bad in 2nd, it should absolutely also be bad in 3, 4 and 5.
follow Lee's recommendations for ruling out less costly issues before considering major surgery.

[deilenberger]

Odd symptom - but exactly the same as one I heard about a long time ago. It's a slipping cush-drive component inside the gearbox.

See: http://www.realoem.com/bmw/showparts.do?model=0572&mospid=47908&btnr=23_0273&hg=23&fg=05

Parts 7, 8 and 9. The idea of this assembly is to take up sudden shock from the driveline and not transmit it to the gears. Problem is - sometimes the spring gets weak, and under acceleration or deacceleration the thing jumps the lobes (it's only supposed to ride up on them partway..) giving exactly the symptoms you describe. I also remember it happening primarily in 2nd gear.

Fix - new gearbox (good used one actually..) A good used gearbox will cost much less than getting the one you have repaired - just the parts needed will cost more than the used gearbox. There are several used parts vendors advertising in the Owners News who can help you out.

[walterK75]

For those of you who offered advice on my problem, I have the verdict. The problem was the transmission. It had apparently been abused to the extent that the shifting drum was worn and shifting was not as smooth as it could have been. A shifting fork was worn down about 50% and the dogs were rounded on 2nd gear. All of this contributed to the slipping problem described in my original post.

The drive shaft splines are fine. The clutch was worn enough that I'd have to replace it soon anyway, so the clutch will be replaced now that it is open.

All of this on a bike with 66,000 kilometers on the odometer. Since it was a police bike, I'm now cautioning people to be wary of buying a used police bike. Have it thoroughly checked by a mechanic you trust and hopefully you won't have to pay for someone else's ignorance and/or abuse.

I'm getting a rebuilt transmission and new clutch. I hope to be riding and get some time in the saddle before the snow comes.

Thanks again for your help.

[breyfogle]

My 1991 K75 clutch seems to be slipping in second gear. .....
Does this sound like a clutch or something more sinister? This just started. The bike has 66,000 kms and used to be a police bike.

BTDT, mine did exactly the same thing. The transmission is beginning to slip out of 2nd gear under heavy load. Mine first did it accelerating in 2nd gear going uphill, thought I had just missed a shift. A few thousand miles later it began to do it accelerating moderately on level ground, I knew I was not missing that many shifts. It will gradually get worse until 2nd gear is unusable. It's time for a tranny rebuild/replacement.