Clutch Slip Diagnosis

albigularis

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So I've been having an odd clutch slip issue with my '09 GS that I got last week.

Basically the clutch was slipping really easily in 3rd-6th. I noticed the fluid reservoir was full to the brim with fluid. I removed some down to the 'max' level and it was better, but I could still get it to slip. I took out yet more fluid to just above the 'min' level and it's better. Now at the point where I can only get it to slip on occasion, usually under wide open throttle at about 6k rpm in 3rd gear.

Full details here.

So I'm pretty sure it's not oil contamination, as there is no oil at the engine-transmission join. And I wouldn't expect it to be getting better with regards to the fluid removal, if the plates had oil on them.

I'm at a loss now, and I need to look at every possible avenue before paying BMW £500 to split the bike in half. Any advice on what else I could possibly check would be most appreciated.
 
As the clutch wears, the fluid in the master cylinder RISES. So it sounds like you may have a worn clutch. How many miles has it done?
 
Take the Starter motor off and measure the clutch plate. New pate approx. 6.5mm, service limit 4.5 mm , Have had them in for change at 3.5mm still driving "just"
 
I had the same with my 2008 GSA, slipping since 10,000 miles if ridden hard in the higher gears.

I bit the bullet and changed my clutch a couple of weekends ago. The new clutch kit costs me £440 from BMW (discounted from £490) so If you have been quoted £500 make sure that is for labour and not just the parts. I was quoted around £1200 for a clutch change. It's only nuts and bolts. New clutch splines were lubed with a molybdenum disulphide grease on reassembly. No more clutch slip issues.

All I found wrong with my old clutch was slight glazing to the friction plate and clutch cover, no oil contamination and 5.85mm of material left after 28,000 miles of use. There was a slight burr on the pushrod which I cleaned off with an oilstone, which may have been the culprit. I believe to remove just the pushrod to check it you need to drop the swing arm.

I did as Mistacat advises and removed the starter to check for wear and oil contamination at 10,000 miles then managed to nurse a further 18,000 out of it until changing it.

EDIT: Check the routing of the hydraulic hose to the slave cylinder, there were issues with the hose getting hot enough to boil the fluid on early bikes. It might be worth bleeding your slave cylinder or replacing the mineral fluid in the clutch hydraulics before committing to a full clutch change.
 
Doesn't help you one bit but it's really odd that it is only slipping in 3rd. A clutch will always slip in top first and then work down the gears as it wears more until it will slip in 1st. 6th and peak torque on a GS is well into the license looser so perhaps you aren't getting there in the higher gears? The more you do this the more rapidly your destroying what is left as well. I would go with Mistacat and get measuring. You will also be able to see oil if that is the problem. No way should the clutch fluid have to be that low to stop it slipping.
Something you could try but I really don't think it will do anything. Bleed the clutch, theory it might reset something. Again I doubt it will work but it's minutes to try.
 
a clutch will always start to slip in top gear and then work down?,sorry disagree with that completely,slip depends on revs and load,torque and power curves will come into play also.
 
My 2010 GS clutch would only slip in 4th-6th gear under full throttle acceleration. The bike had done 20k but AFAIK its still running nearly two years later with no problem.
 
You've checked the usual reason for clutch slip........lever snagging on the handguard? :rob
 
Miff said:
As the clutch wears, the fluid in the master cylinder RISES. So it sounds like you may have a worn clutch. How many miles has it done?
Click to expand...

It's done 16k miles, has full BMW service history, last service being 200 miles ago.

Watty100 said:
You've checked the usual reason for clutch slip........lever snagging on the handguard? :rob
Click to expand...

Yeah, was one of the first things I checked, the lever is miles off the handguard. I've got small hands so the lever is way in.

I'll get the starter motor off and check the plate measurement shortly. I don't see why it would slip if it was worn down unless it was at the point where it was so worn that it was unuseable. It's also disappointing that if that's the case, the clutch on this big beast of a bike can't handle 16k miles worth of hard use. It also makes me worry, as I use my bike for fast paced weekend rides sometimes.
 
There is also a handy cover at top of clutch housing. Only snag of the airbox gets the way and that's trapped by back subframe.
How helpful am I. ?
 
Bendy toy said:
There is also a handy cover at top of clutch housing. Only snag of the airbox gets the way and that's trapped by back subframe.
How helpful am I. ?
Click to expand...

Do you have a photo or diagram that shows this?

I tried to get the starter off today, but the only T-45 I have is part of a crappy drill bit set, and it wont even fit into the screw head properly. I don't want to round the head off getting it out.
 
"a clutch will always start to slip in top gear and then work down?,sorry disagree with that completely,slip depends on revs and load,torque and power curves will come into play also. "
Sorry I disagrre with you the guy is perfectly correct assuming the bike is being ridden through the normal rev range in all gears. If the bike does not slip the clutch in top at 6k ish under load then it is fair to say it will not slip in third at the same revs, however if the bike does slip in top at 6k under load that does not mean it will show a slip situation in third at the same revs and loading... so he is correct belt up and stop talking pish! It is the standard way to test a clutch on a bike that is a possible purchase.
 
If really desperate, and money is tight:

Go to you local music shop.
Buy a block of resin. (used on violin bows to make the strings resonate)
Powder some of it, remove starter, and with clutch lever pulled in,
endeavour to get the powder onto the friction surfaces of the plate.
If you succeed, all clutch slip will vanish. The clutch will be quite "grabby"
but it works well.
In a past life, this was common practice in rally cars, and one bored a hole in the
top of the bell housing to make it easy to drop the powder in.
Myke
 
A failing clutch will slip first in the higher gears as it gets worse the slip happens in lower gears. By then the rivets may well have scored the pressure plate.
 
Random question butdo you use the side stand more then the centre stand?
Only reson I ask is that I "used" to have a problem with clutch slip but now I use the centre stand I've not yet since had a problem believe it or not at the time my bike hasd only done 6k it now nearer 20k and zero issues since

Just a thought!
 
X21ekx said:
Random question butdo you use the side stand more then the centre stand?
Only reason I ask is that I "used" to have a problem with clutch slip but now I use the centre stand I've not yet since had a problem believe it or not at the time my bike has only done 6k it now nearer 20k and zero issues since

Just a thought!
Click to expand...
More importantly:
Which side do you dress to?
Myke
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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