Slipping Clutch - or not ???????

[Richard P]

Well, after my 1150gs letting me down a couple of weeks ago - apparent clutch slip after approx 30 miles (luckily approx 5 miles from home) and ok again after the engine has cooled down, I finally with the help of my good friend Gordon, stripped it down today.

Much to our surprise, although there was a small amount of oil in the slave cylinder assembly, the clutch side was dry with no apparent leakage.

On removal of the push rod there was no oil on the clutch side of the felt washer although there was on the slave cylinder side.

There was no oil around the gearbox bearing at the clutch side.

The bike has only done 12,900 miles.

Any suggestions ? the bike is still in bits awaiting my ordering of parts ( as recomended by Sherlocks)

One disturbing thing that we did find was that on removal of the rear wheel, both of the brake pads collapsed - not something that I would have wanted to discover whilst moving.

 

[Richard P]

.............

 

[Colban]

First of all...who did the 12K mile service and didn't spot knackered pads?.
Before you stripped it down,did you check if the clutch lever was fouling the handguard and also,was the clutch fluid level correct? ie not overfilled.
How do the clutch plates look-oily?.Is there any trace of oil splashed around in the clutch housing?.The seals that can go are the engine output seal and the gearbox input seal-any problems here.The clutch slave cylinder leaking/failing is not a rare problem either.

 

[Richard P]

The 12,000 hasn't been done yet - I will be ordering the parts for a major service at the same time as the clutch parts.

There was no sign of oil contamination either on or around the clutch plates or housing, just sooty dust deposits presumably from clutch plate wear and there wasn't a lot of that

As I said before, there was no sign of oil on the clutch side of the push rod or the bearing end between the gearbox and the clutch. The clutch didn't look particularly worn - no sign of a hard life in the first 8k which I wasn't involved in.

Sherlocks had advised me to strip the clutch down and see which parts to order but I guess I'm at a bit of a loss to know which ones to go for.

 

[Steptoe]

measure the thickness of the friction plate. Min is 4.8mm , a new plate is approx 6.3 - 6.6mm

If it's been slipping i'd replace the complete clutch unit. The cover and pressure plate will have got hot and the surface faces will be fecked, although they may look ok.

 

[Richard P]

Thanks, the bike isn't at home so I will measure it up tomorrow night

I was wondering that if it wasn't the clutch, could it be the drive shaft ?

If so would there be any outward signs

 

[fundura]

Jeez,Only 1.5mm between a new clutch plate and a worn out one Don't seem much?

 

[Colban]

I was wondering that if it wasn't the clutch, could it be the drive shaft ?

If so would there be any outward signs

It could very well be the driveshaft.Its been known for the bonding between the outer and inner parts of the shaft to become unstuck (usually after abuse) and give the same symptons as a slipping clutch.
If its out of the bike,have sniff for a burnt rubber smell or any bonding loose.

 

[Colban]

Jeez,Only 1.5mm between a new clutch plate and a worn out one Don't seem much?

Although i had to change mine at 54K,there was still plenty of meat on the friction plate,but the splines were badly worn.They can go 100K plus.
A bit of a design flaw there as well as a lack of spline lube.

 

[Richard P]

I'll have a sniff of the drive shaft tomorrow as well

Any other possibilities out there ??

 

[Richard P]

5.1mm of clutch left so not below service limit

 

[Steptoe]

5.1mm of clutch left so not below service limit

Replace it.

 

[DrFarkoff]

Perhaps a weak pressure diapraghm? at that low a mileage I would not expect a clutch failure!

I had one that the clutch slave cylinder bearing seized in and caused mayhem with the clutch, but that was more to do with not being able to disengage, What Fun bringing that one home in traffic!!!!

Clutch pushrod jamming not returning to it's rest position when hot?

Did anyone perhaps top up the clutch fluid? Heat = expansion and no extra space = expansion of the slave cyl It would only take a little pressure to remove the clamping effect of the pressure plate

I'd do what Steptoe says and replace it all then you have removed the main component of failure but I'd check the clutch operation bits too and flush the hydraulics thru too

 

[Richard P]

Quick update - nearly finished !!!

Got replacement clutch kit from Sherlocks excellent next day service along with a replacement slave cylinder end seal and a major service kit.

Main problem in stripping down the bike was the heating up and loosening of the 2 transmission bolts rest just took a long time

Replaced clutch, no big problems. Tried Tsiklonaut's technique of using the gearbox to centre the clutch but found that it caught the inside of the housing so it could not be rotated. Resorted to using dowel to line it up and we managed to locate the gearbox first try.

Removal of the slave cylinder seal was a right prat, had to break it up to remove it.

Did not realise until we came to re-fit the swinging arm that it has to be separated at the final drive end as well. 2 more bolts to heat up and a huge amount of time and effort to move them - another right prat of a job.

Rather worryingly there seemed to be a lot of little pieces of black matter (rubber??) inside. I wonder if this is a sign of breakdown inside the drive shaft ? time will tell I guess.

Anyone out there have a spare one ???

Not quite finished yet wires and pipes to tidy up, battery and tank to go back on tomorrow night then to test it..................

 

[Steptoe]

Rather worryingly there seemed to be a lot of little pieces of black matter (rubber??) inside. I wonder if this is a sign of breakdown inside the drive shaft ? time will tell I guess.

That could be the cause of your "clutch" slip

The drive shaft is spinning in its cush drive.

 

[Richard P]

Thanks Steptoe

Just finished putting it all back together from the clutch fix

It ran ok from Beverley to home ( approx 15 miles )

Assuming that it is the drive shaft, would that explain the slip when "hot", work when "cold" symptoms ?

 

[Richard P]

Just fitted a s/h driveshaft from a 10,000 miler courtesy of Sherlocks

Gave it the jelly up and down a local dual carriageway and so far all seems fine ( it slipped under these conditions previously)

Anyway, assuming that's the end of the issue, if you appear to have a slipping clutch that gets better when when the engine cools down again, check the inside of the swinging arm.

If it's covered in "crumbs" of black rubber, you may well have a knackered drive shaft.

It's a much easier / shorter / cheaper job than replacing the clutch.

Thanks Steptoe, now for the trip round the Baltic............................

 

[delpel]

Well done chap. It's one heck of a way to get to get to know your bike.

Good luck with your trip and give us a shout when you get back and maybe we can organise a ride or two.

 

[Richard P]

Will most likely be going for a ride out before that - will let you know