Hello community
I'm experiencing the following:
When bike takes a ride more than 50km distance and speeds more than 140km/h the clutch starts slipping at 3rd, 4rth & 5th gears
Next day i ride for 25km distance and no slipping at all. 
That behaviour occurred 3-4 times in the same sequence
Any ideas?

Reset your clutch adjustment then take another ride. Read all of the attached instructions here carefully before beginning the procedure. The first image is from a BMW workshop manual. The second is from an early K100 riders manual.

Note that you'll be making adjustments at the clutch hand lever twice—once for setting the exposed cable length then again after setting the correct contact of the clutch arm bolt against the piston. I check clutch hand lever free play by pushing against the end of the hand lever with one finger. That works for my bike.



From the 1984 K100 Rider's Manual


If the clutch cable, clutch arm bolt and hand lever adjustments seem correct but the problem still persists then you will likely need to access the clutch pack to investigate for friction disc wear or another condition.

Thanks Laitch!
What confuses me is the fact that it comes and goes . If it was the clutch plate i guess it would slip all the time. Also affraid of contamination of the clutch plate through a seal either from engine oil or transmission oil into it. Maybe its a dumb thought, but i was thinking when bike gets hot and pressure is developed in the oil departments maybe then it escapes through bad seals and resides on the clutch plate causing slip. 
Just saying.. 

George_Pap wrote:Just saying.. 

You're over-thinking, George. Have an espresso; do the adjustment. If it doesn't work, open your schedule for hypothesizing.

Laitch wrote:

George_Pap wrote:Just saying.. 

You're over-thinking, George. Have an espresso; do the adjustment. If it doesn't work, open your schedule for hypothesizing.

hahaha! I really do mate  Thank god its Friday so another K weekend

George if the seals were actually leaking enough to cause clutch slip, there would be other evidence. Check the weep hole where the engine and gearbox intersect. And take the time to adjust the clutch properly.

Regards Martin.

Just dived under the gearbox and found out that probably this is seal leaking so the clutch plate must be contaminated
Correct?

George_Pap wrote:Just dived under the gearbox and found out that probably this is seal leaking so the clutch plate must be contaminated
Correct?

Not necessarily.

It is possible for shaft seals to leak but not contaminate the friction disc. What you've shown in your photos doesn't indicate to me much of a leak or whether it is motor oil or transmission oil that might be leaking. It is grimy for certain and not something to be shown to guests until it is cleaned up.   If fluid is pooling on the patio floor then running downhill into the local bakery, that would call for some action—maybe putting a pan under the moto to catch the oil for reuse or resale.

Furthermore, sometimes these bikes can be ridden pleasurably for thousands—maybe tens of thousands—of miles with intermittently slipping clutches and oil leaking from around the shaft, as long as the oil is replaced and the clutch operated with finesse. Just stop attempting to do wheelies.

Doesn't trying a simple adjustment then testing its effect interest you, George? Have you already adjusted the clutch and it continued slipping, or do you just feel uneasy with the idea of contentment?

Espresso ☞ clutch adjustment ☞ ride ☞ resume morose contemplation.

Thank you Laitch. Your reply let me cool down a bit. Yes I have adjusted the clutch cable as per BMW manual you sent me. I took it for a small ride due to lack of time and had no signs of slipping but for sure I will now at Monday that I ll have to commute for more than 60km for a photoshooting.
I have never seen a single drop on the floor under the bike. I really can't tell if it's transmition oil since it's too muddy.
So I stop looking for parts and I ll be studying it's behaviour.

George_Pap wrote:So I stop looking for parts and I ll be studying it's behaviour.

Don't forget to enjoy its behavior while studying it, George. Have an enjoyable ride.

I really do enjoy it Laitch!!!

Transmission oil has a very distinct aroma! very different to engine oil. If you have some old bottles of oil then you could 'calibrate' your nose by having a sniff.

Mike

Mate I'd be inclined to inspect the cable, just incase it is a bit frayed and that is catching and not letting the clutch lever at the gearbox set fully home. Or perhaps the lever is in need of a lube to free it up more.

Sort the easy options first and cable and the pivot arm bearings being seized up would be top of that list. As said check too for hidden fraying.....I must admit whenever I got a new bike it always got a full service and a new clutch cable as a minimum. Always with a K too and I had a mighty stiff clutch on the K1100LT when I got it...new cable solved it and it's now a one finger operation.

Be careful if you disconnect the cable not to let the pivot arm rip the cutch pushrod boot.

If all that doesn't sort it then you are looking at getting in there by way of clutch spline lube but erratic slipping points to the cable and pivot arm first.

92KK 84WW Olaf wrote:Sort the easy options first and cable and the pivot arm bearings being seized up would be top of that list. As said check too for hidden fraying.....

Hear, hear.

As a mechanic, friends have often described their issues to me then jumped straight to the most complicated and expensive possible solution, when it was often (though not always) something much easier and cheaper.
Sometimes they've told me before they start, and I've given similar advice to Olaf, often with money-saving success. Sometimes they've asked me after they've spent money and then had to go back to the simple and cheap.
Sadly, there are always times when time consuming and expensive is actually the solution. 

Bill

George I'm still on my original 26 year old cables. I added a grease nipple to the clutch arm, and every second service I lubricate all my cables with a PTFE based lubricant called Triflow which is compatible with Teflon lined cables. Never use WD40 or it's like, as they can degrade the Teflon liner.
Regards Martin.