R1150R weird clutch slave stuff

[MIXR]

Ok - Long story cut short but I have some weird symptoms related to a slipping clutch and I am out of ideas.

Clutch started high-gear slipping under load about 5,000 kms ago.

It was not a very old clutch and was not worn out.

We pulled the bike down. Clutch looked fine apart from some spline grease splatter.

Slave was a little bit sticky, but cleaned up well and seemed to function just fine. No leaks. Seemed smooth when cleaned up.

We decided not to refit the same clutch, even though it was looking good.

I had an original clutch (complete assembly) from the bike that was known to be good when removed some time previously while the bike was apart for other reasons. So we put in the known good clutch.

The same slave also went back in. Working fine and not leaking.

Fast-forward to now.

Clutch started slipping again in higher gears under load. Usual stuff from these bikes.

We suspected the slave as it was the only part not changed last time and ordered a new one (Beemer Boneyard).

While replacing it, we found a corroded main clutch line that started leaking. We had a new one made.

So ............. We have an old but known good clutch, a new slave, and a new clutch line fitted.

The system was bled manually.

Test ride was ok for a while, but then the same slip came back!

We re-bled the clutch because I know this can be a bugger of a job to get all air out. Only got a small bubble of air from the system.

Test ride was ok for a longer time, but then suddenly same symptoms are back with a slipping clutch.

So what am I missing here?

Two clutches have slipped. The slave has now been replaced. The main clutch line has been replaced. The system seems to bleed out ok.

Surely I don't need a third clutch?

First one had 90,000 kms on it and service guys who replaced it said it it had at least another 30-40,000 kms or more to go as I was only doing long distance riding. It was not slipping when removed and is the one in the bike now. Second one had 65,000 kms of long distance riding. It's the one that started slipping 5,000 kms ago and was removed and found to be in good condition. There was less than 0.6 mm wear difference between the two, but I didn't write down the overall measurements. Either could have been used, but we went with a known good one as they were pretty much on par. I still have the 'newer' one in the shed.

Any clues on what else I should look at? Expert comments welcomed. Mick.

[Clay Spinner]

The easy answer... did you adjust the actuation arm on the back of the gearbox?

[Steptoe]

Check the driveshaft - the rubber insert which acts as a shock absorber can slip giving the same symptoms of clutch slip.

Pull back the final drive and look for rubber granules in the swingarm, or melted rubber on the shaft drive insert.

[MIXR]

Gear actuation arm wasn't touched. Never even considered that it would need it, let alone look it up and fiddle with it when we replaced the clutch the second time. Edit - This is an R1150R, not cable operated R1100

Only other thing we have come up with is whether there could be an issue with the master cylinder. If the 'return' port is partially blocked, then maybe the clutch slave fluid eventually gets hot enough to partially actuate the slave instead of going 'neutral' back at the master end?

Oh well, that's a couple of things to look at, but the clutch was working fine for 65,000 kms (Clutch B) and again for 5,000 kms (Refit good clutch A), and still works fine when the thing has been bled and is cold.

Definitely a temperature factor there somewhere.

[MIXR]

Originally Posted by Steptoe

Check the driveshaft - the rubber insert which acts as a shock absorber can slip giving the same symptoms of clutch slip.

Pull back the final drive and look for rubber granules in the swingarm, or melted rubber on the shaft drive insert.

Wouldn't that give a permanent slip? I'll look at it, but can't see how it would work cold and then slip hot. The clutch definitely 'flares' with RPM and load when everything gets hot. It's fine cold. Gotta be hydraulics.

By the way, there are no leaks at the main shaft and the clutch looks as clean and dry as when it went in as seen from the timing port and when the starter was out.

[MIXR]

Clay Spinner - Can't see that the actuation arm has anything to do with the clutch operation and slip. If you know something more about that, please post again.

Steptoe - Pulled the final drive boot back. I've never had to remove this drive so it's the 160,000 km original (did my GSA earlier in the year). Out came about 10-15 ml of very old oily stuff, but no bits of rubber. I suspect the 'oil' has been there a very long time. Had that aged dirty look and feel. I checked the rear diff oil level and gearbox oil level. Both are where they should be (full to the threads) so no oil has been lost that is obvious. There was enough in the boot to probably show in the level, but the boot has not been disturbed since at least 2007 (if then) and that was about the time the 'new' clutch went in, so around 65,000 km ago. I also checked up the hollow drive shaft casing. There are no 'trails' that indicate any oil has been seeping down from the gearbox end of the shaft. Also, no evidence that the rear drive unit has been leaking forward into the boot. No idea when, where or how it got there. It almost seemed to be too 'light' to be gearbox or diff oil. I did note that the zipties on the boot were not as tight as they could have been, so maybe a collection of degreaser worked its way under the boot?

Back to the clutch slip, I'm still thinking that the master cylinder might be involved, but haven't done much with that, so it's a bit of an unknown.

By the way - I used to own this bike but a work mate now owns it. He's had it for over a year but only done around 5,000 kms. It does a lot of shed-sitting. Not that that should have an effect.

[PETDOC]

Originally Posted by Steptoe

Pull back the final drive and look for rubber granules in the swingarm, or melted rubber on the shaft drive insert.

Couldn't you also just shine a light up the shaft from the rear and see it was out of phase to document this defect? I guess there would be the odd chance it would catch again in phase, but not likely.

[def]

Originally Posted by PETDOC

Couldn't you also just shine a light up the shaft from the rear and see it was out of phase to document this defect? I guess there would be the odd chance it would catch again in phase, but not likely.

?

[JPSpen]

You've about run out of stuff to look at...

Are you sure the clutch disk is good ? Some times they can be contaminated with oil and cleaned up and look ok but will still slip...

Maybe reverse bleed the slave cylinder.. If it's got a bubble in it.. That could be getting hot and causing a partial actuation... But that really, really takes a lot of force to partially actuate the clutch..That's grabbing at straws...

I guess you could take it out and get it hot to where the clutch slips then crack the bleeder and see if you have pressure on the clutch...

Maybe a weak mainspring ? Seems like I read where someone got the spring reversed and that caused the clutch to slip...

Good luck and let us know what you find...

John

[PETDOC]

Originally Posted by def

?

Go to bottom of link for drive shaft phasing. http://jniolon.clubfte.com/driveline...nephasing.html
Whenever I pull the rear drive off my GS I always use a flashlight to set the front U-joint to match my rear so they are in phase. If the rubber "shock" connection in the drive shaft is slipping as mentioned by Steptoe then the front and rear of the drive shaft will rotate independently when slipping and when they lock up again the odds of the U-joints being in phase would be pretty low.

[PETDOC]

[QUOTE=MIXR;19230918
So what am I missing here?

Any clues on what else I should look at? Expert comments welcomed. Mick.[/QUOTE]

If you overfill the main clutch reservoir it can "pressurize" the clutch system and cause it to slip.
Did you replace the diaphragm spring when you swapped out the clutch?

[Jim Moore]

If you had air in your line you (maybe) wouldn't be able to disnegage the clutch. You have the opposite problem, so I don't think that's the answer.

There was a guy on here within the past year who had a similar problem. It turned out to be the drive shaft. Worked fine when cold, started slipping when hot. You could tell if you could get a look up the tunnel. There will be rubber splatter inside the swingarm.Removing the final drive will give you the best view. You might be able to get a look just by pulling back the boot.

[Steptoe]

Originally Posted by MIXR

Clay Spinner - Can't see that the actuation arm has anything to do with the clutch operation and slip. If you know something more about that, please post again.

.

Clay spinner has his models confused -the 1100 has an actuation arm. The 1150 is hydraulic.

Thought you'd know that as you've just replaced a clutch ????

Are you replacing just the friciton plate and still using the pressure and cover plate, or have you replaced the complete unit.
The cover and pressure plate also get surface wear.

[Mrmerlin]

if you dont find any rubber in the swing arm from the driveshaft then you would be well off to replace the complete clutch assembly.
simply swapping a new or thicker used disc wont make up for the wear of the PP or the clamping ring,
and these parts do wear though it wont be obvious,
the wear will be radially
IE the inner circumference will be worn down more than the outer area.
This can be checked with a straight edge placed across the parts.

The other part that will be damaged from heat is the diaphragm spring,
once it gets hot it will lose its tension,
and thus lose its ability to supply the correct pressure to the clutch pack
, this compounded with worn clutch components will lead to slipping.
SO swap in a whole new clutch pack and spring and drive!

[ragtoplvr]

OK, here are some things in no particular order.

1. Remove the cover of the clutch master cylinder. Cover the paint with a wet towel. Press the lever, there should be a strong spurt of fluid, if not then you have a Master Cylinder problem.

2. The clutch cover and friction plate in the flywheel will wear dish shaped, more wear on the inside. A different disk is not worn to this shape, and that alone is enough to cause a slip until it beds, which can take over 10K miles.

3. The diaphragm spring can get weak, there is a specification for it.

4. The rubber hose can break down internally, and block return fluid. Probably about time to go the a good set anyway.

Rod