Hi there everyone.
I have a 1986 K100rs which I recently purchased from a very caring owner. He completed a lot of the work on the bike himself and it is in amazing condition. He rebuilt the transmission and clutch about 500kms ago and the bike has a shudder on takeoff and I believe the clutch is slipping, particularly under load in 3rd. Is there anything I can do to both check and rectify or is it back to the mechanics?
Thanks for any advice
PAUL

Check the clutch cable and lever for free motion when it is disconnected from the clutch(be sure to support the clutch arm to avoid tearing the $40 clutch boot).  Then check the clutch arm on the rear of the transmission for free motion.  Both should move freely without any binding.  The clutch arm is vulnerable to sticky action because of the bearings it rides on down near the bottom of the engine where it is exposed to all kinds of dirt and water.  Some owners install a grease fitting there to keep the bearings clean and lubricated.

If all is well, do a careful clutch cable adjustment.  Then get back to us and let us know how you made out.

If you can, ask the previous Owner if he replaced the pressure and fixed drive plate. The plates can get warped and if not rectified shuddering is quite on the cards. Also the K100 pressure and drive plates have a bad habit of getting dished so that when a new friction plate is used there is a bare 5-6mm at the outside edge actually in contact which is enough to drive but as soon as the wick is turned up it slips.
Do the easy and simple adjustments first as point seven five has suggested but I would be betting on the clutch itself is where the problem is.

You might also question the PO as to how he went about greasing the gearbox input shaft splines / clutch disc spline. If he applied any lube to the internal clutch disc splines, it is likely that some of this has ended up where it gets thrown off and contaminates friction linings...

Quickest way forward may be to operate the clutch when stationary and then immediately see if you can detect free play between clutch operating arm in the direction that it moves when you pull the clutch lever in. Unless you are sure that this free play exists, you better go with 0.75's recommendation. If I did this test and was convinced that the lever / cable / operating arm arrangement was not maintaining constant pressure on the back of the clutch operating rod mechanism, then I would go straight for the checks that Rick describes

Having messed with a lot of old K bikes, even if those clutch arm pivot rod needle bearings are in really bed shape the bike will still shift pretty well. I think this is mostly due to the leverage of the clutch lever and clutch arm geometry.

I don't think most owners even realize that those bearings exist.

I do though and re-lube them whenever I do a clutch spline lube.

As for fouling the clutch plate, that only happens if the spline lube is pushed through to the front.  Any excess at the back stands off from spinning onto the friction surface due to the collar on the clutch plate. Any excess at the back will just spin off to the interior of the bellhousing.

I always clean out the old stuff, make sure there is no excess on the tip of the drive shaft and then put tons of lube on the splines.

is there anywhere on the net that will show me how to check for correct clutch lever adjustment.
Thanks
Paul

There should be 75mm of exposed inner cable between the end of the cable adjuster and the clutch arm. It's simple enough to adjust:

1. Disconnect the cable at the lever
2. At the back of the clutch arm is an adjuster bolt and locking nut
3. Set the distance between the clutch arm and the end of the cable adjuster by turning the clutch arm adjuster (jeez! too many adjusters around here!)
4. Lock it up
5. Reconnect the top of the cable into the clutch lever and set the slack to suit you.

I had a similar problem where the clutch would slip under heavy load (i.e. gunning it!) and assumed that at 70,000 miles the friction plate was on the way out. I set the clutch adjustment correctly and 7000 miles later it's still giving no trouble.


[Edit] I see Rob's posted the link to Duck's writeup. I couldn't find that initially.

Hello!
Not much to add, Dai and robmack already said.

I had the same issue and adjusted the clutch on all my Ks, I cut a pice of metal with the length of 75mm, to measure correct.
I also used the best Gear oil for the Ks, Motul SAE 75W 140 helps.
One Liter is enough for the gearbox AND the final drive, if you start at the final drive, till the bottom of the final drive hole and the rest into the gearbox. The oil is more expensive then the normal gearbox oil but worth it! :-)
The issue was solved.

Cheers

Dai wrote:1. Disconnect the cable at the lever
2. At the back of the clutch arm is an adjuster bolt and locking nut
3. Set the distance between the clutch arm and the end of the cable adjuster by turning the clutch arm adjuster (jeez! too many adjusters around here!)
4. Lock it up
5. Reconnect the top of the cable into the clutch lever and set the slack to suit you.

Around the other way I think Dai. But at the end of the day you might (??) end up with the same result me thinks.
I use the method described in the Haynes manual which is basically the same as the BMW service manual as per the excerpt in Robert's link except the cable is not disconnected. It says to adjust for 75mm at the bottom of the cable by adjusting the adjuster on the top hand lever, not the clutch arm adjuster. That's for adjusting for zero play. Then adjust for 4mm play at the top hand lever.

That serves me right for relying on memory and not Haynes! Sorry for the misleading info, Spicepaul.