Bugger. Me clutch's gone? Or maybe not?

[Ixion]

Odd. Took the BMW to have a new tyre fitted this arvo. All fine over to the Shore and back to Wiri. Come time to go home, jump on , start up, onto the road - WTF? Clutch is sllipping like mad. Stop, check cable adjustment, look for anything obvious, nothing. Off again, still slipping. No noises, no judders or jerks, just slips at anything over about 2500 rpm. Seems Ok up to that point. Limp slowly home - not too bad, cos I can still take off from a standstill OK, and 2500 RPM is about 70kph in top.

Get home, wozza matter wiv the bastidge? Clutch plate gone? Not the usual symptoms, and no warning at all . Splines rooted temselves? No noises or jerks, seems too smooth. Pull the rear wheel off and slip the cable off, and slacken off and readjust the pushrod adjustment (Yes, you do have to take the wheel off, it's a BMW don't expect anything normal). Hmm, everything looks OK. Unfortunately, a clutch on a BMW is a BIG job - not like a normal bike. Well, ever the idiot optimist, I'll just try resetting the pushrod, and reassemble. On the thousand to one chance. And bugger me, do so, onto the road, and it seems fine. Pulls away from 1500rpm in top with no slip, runs up to peak revs, no sign of slip.
Very odd. Very odd indeed. Problem is, now I don't trust it. Anyone ever encountered such a happening?

[HDTboy]

Is it a dry clutch? If so is there oil on the plate or leaking out of the bellhousing?
If you dump the clutch in dop gear (as hard as it sounds) you'll soon know if it's going to slip or do wheelstands

[Ixion]

Yeah, I thought of a seal blowing and soaking it in oil (it is a dry clutch). But no oil leaks, and an oil soaked clutch won't right itself. It doesn't slip under hard take off - (don't fancy slipping sideways off the clutch lever on a shaft drive, theres nothing to coushion the blow, you can break a tooth off the pinion that way).

[HDTboy]

How many times have you done it in a car without worrying about the crownwheel, I could give experience a call tomorrow if you like

[Ixion]

I'll just wait and see - it's not slipping now. I have seen something like this once in a car where a bit of lining broke away and got bent back and caught between the (unbroken away) friction surface and the pressure plate - so there was only a very small area taking the load. When the broken bit broke away completely it "fixed" itself. I think I better think about scheduling a pull down sometime soon, probably a good idea to lubes the splines if nothjing else. Least I may be able to do it at my convenience, anyway

Thanks anyway.

(Uh, never in a car - I don't like abusing machinery if I don't have to. I've seen a good many pinions and crownwheels with broken teeth though)

[N4CR]

Well after you have gone past me now twice sitting on the tank on one wheel - I'm not suprised.

I have no idea how these things work but mabey a minor oil blockage and it got dry or something!?

[Mooch]

Was the rear tyre getting replaced by any chance ? .... Have you checked the rear gaurd for small chunks of rubber ?. If you find small bits someone may have finished off the rear trye and your clutch at the same time.

[Ixion]

No, it was the front. And I watched them do it.

[Ixion]

UPDATE: Rode it to werk today, then into the city and back. No problems at all, no slipping. So buggered if I know what that was about , but at least it hasn't cost me any money . Yet. OK now, so that rules out most common clutch deamons. Could still be the lining shredding off - in which case I'll know soon enough I guess.

Literature search turned up one other possibility - the pushrod actuating arm pivots on a shaft which in turn is supported in two needle roller bearings. Which have a (mild) reputation for crapping out. On account of no-one made any provision to lubricate them. Thought the Herrenvolk were supposed to be through. I have known crapped out needle rollers to partially seize as broken rollers jam up, thus maybe preventing the arm returning fully. And my resetting adjustments freed things up. Maybe . Perhaps. I'll put pulling the bearings out and checking them on my list of "Stuff to get round to when I have some spare time". 'Tis a long list, that, but.

Anyway, it's all good for the moment.

[Motu]

I've been thinking about this all day,a tricky one alright...but think I've got it sorted.My diagnosis? - Senior Moment.....

[Ixion]

Took him for a WoF today, then on to werk, all good. Stop at the servo on the way home for petrol, set out again, and it's all revs and no action!

But this time I stopped and investigated.

Peering suspiciously and critically at the pushrod actuating mechanism. Looks ok, and a tentative prod with a finger (access is limited) seems like it is fully back . And pulling the lever in and out, and such like makes no difference.

But. But. When I deployed BMW special tool IX-001-A (aka, my umbrella) in a retrograde axial aspect, in conjunction with BMW special tool IX-002-B (aka a BLOODY BIG ROCK that came conveniently to hand from a nearby garden feature, very obliging of BMW to provide convenient roadside repositories of special tools) a further 3/8" or so of movement resulted (in technical terms, I stuck my brolly through the swing arm to prod the clutch actuating arm, and gave it a blurdy good whack wiv de rock ) .

And then the clutch clutched like a clutch did orta clutch.

So I think I must move investigation of those needle rollers higher up the list.

(BTW, I am always surprised at how few motorcyclists carry an umbrella. The folding variety are small enough easily to be accommodated - bungy them to a convenient frame member. And I have many times found the brolly to be useful - as well as it being very handy for keeping dry in the rain, of course.Word to the wise)

[raster]

Hope you get The White Wale sorted, I'm sorry I haven't got any bright ideas for you, I ended up breaking my clutch:angry2:

[Motu]

So do you reckon a trampoline spring hooked onto the lever and back to a hole you can drill in the swing arm will fix it?....



I'm sleeping on my tramp tonight....just incase you get ideas...

[Ixion]

That's OK - I just need the springs. Suggest you put something soft under the tramp.

[Milky]

I believe that the later clutch actuation systems are much improved on the earlier ones. They went from thrust ball bearings to radial needle roller to radial needle roller + integral hingey thingy AFAIK. It is not an unheard of problem for these bearings to fail.

As an aside, do you have the requisite grease for the clutch splines?

[Ixion]

Ah the wonderful controversy about the right gunk to use on BMW splines. I follow the heretics and use HondaMoly60.

But it is not the clutch thrust bearing that is suspect. The clutch cable connects to an actuating arm, pivoting at the rear of the gearbox. That arm runs across the bike in front of the rear wheel, and at the opposite end to the cable, bears on the clutch pushrod. (It's BMW. Expect wierd). The aforesaid actuating arm is pivoted on a shaft running crosswise, supported at either end by small needle rollers. These have no provision for lubrication, and have a history of breaking up . Which I suspect is what has happened, the needle rollers have snapped and every so often the bearing jams up on a bit of broken roller. Thus the actuating arm does not come fully back (there is no spring to return it, it relies on being pushed back by the clutch pushrod, good engineering Mein Herren) and the clutch is left slightly disengaged. Unfortuantely getting at the bearings is (apparently) a bit complicated, the footrest hangers have to come off, which means removing the exhaust, and the ABS units , and , and , and .

[Motu]

The BMW clutch spline lube issue has always puzzled me - it's an inline dry clutch drive,truely a 100 year old design that was perfected when Hitler was still in nappies.So how come regular clutch spline lube is a regular maintanence issue? Do you send your car in every year for the clutch splines to be lubed? This is a huge colosal fuckup from BMW and I'm surpised some Yank hasn't taken them to task over it.How can you fuck up something the rest of the industry has been doing perfectly for 100 years?

[Ixion]

Well, an update, an possible explanation.

The odd slipping did not reoccur. But, I started to observe slight clutch slip of the "normal" variety. Not bad but there.

And coupled with the lingering suspicion, and a twitching conscience about not yet having lubed all those splines. Or checked the universal joints.And fretting about what condition they might be in (Just don't start me off on this one - like Mr Motu I cannot comprhend how BMW can get away with it. Millions of cars on the road with the same arrangment , not one of them needs the transmission pulled apart every year for lubrication)

So, I decided I'd better summon up my courage and pull it down.

Not too bad actually, the actual clutch/gearbox bit is pretty straight forward. Bad bit is the amunt of stuff you have to pull of to get there, including FI computer, ABS computer, ABS units, wheel sensors , all sorts of "don't come near me if you know what's good for you" stuff.

Finally pulled the gearbox out, and stripped out the clutch.

No sign of oil, a bit of thick dust , but no evidence of leaking from either end.

Mic'ed the old plate , only 1 mm under standard. Hmm, 1mm isn't a lot of wear, could that account for the clutch slip? Until I compared it with the new plate. Hm, yes, 1 mm IS a lot of wear when you're talking clutch plates. The friction plate was worn bevelled too, nearly 10 thou difference between inner and out circumferential thickness. Not good ,that, and the clutch friction hub isn't sprung so there's no give to take it up. Very crude clutch looks like something out of a Model A Ford.

But, looking at the old friction plate I think maybe I see the reason for the original strange behaviour. In one face of the clutch plate , there are a lot of deep gouges and scores. I do mean deep, nearly through the thickness of the friction lining. Not much surface area in aggregate, but quite a lot of them .Only thing I can think of doing that sort of damage is a small hard foreign body getting between the friction plate and the pressure plate. Keeping them from making proper contact until the foreign body is either forced into the friction material (hence the gouges) or spat out. But until then, the clutch plates would hardly touch at all.

Certainly nothing like any normal sort of wear. *Very* thorough examination of all the bits shows no sign of any broken off metal bit that could account for it. But, grubbing about in the recesses of the bell housing casting I extracted a number (about a dozen) small hard granitey stones, up to maybe 3/16 diameter (though not circular). Guess one of them could have done the job. How did they get there. Only thing I can think of is they came in through the largish drain hole at the bottom of the bell housing. I guess that on gravel roads, or roadworks (some appeared to be tar coated) the bottom of the bike must be subjected to quite a fusillade.

The pressure plate when carefully straight edged showed several thou deformation on the mounting tabs. so I replaced it too. If I'd been on a tight budget , I'd have just dressed the tabs down with a fine file or a surface plate. But I was lazy , and did it by the book. Other than that , only parts required were 6 retaining allen bolts and 6 shake proof washers for ditto . All ex stock at Experience BMW. Who kindly gave me sufficient of the super duper special BMW spline lubricant , for free, to do all my splines. Very kind of them, it's pricey stuff and a whole tube would last a lifetime..

Oh, my splines were perfect , as were my universals. No wear at all.

I pulled off that suspect linkage arm. It felt dry and stiff though not rough. No grease nipples or provision for lubricating it.(grrr. Can I have a word , Mein Herr Designer) . So I did the old trick of boiling it up in a pot of grease. Felt much better after that . Smelly business though, hopefully Mrs Ixion will start talking to me again in a few weeks time.

Reassembly was straight forward, other than having to turn up a mandrel to centre the clutch. I did a dummy run by eye, but decided the mandrel was a neccesity. The official BMW tool is a pretty thing, got knurling on the handle and everyfing fancy like, but costs nearly $100. Hm, too rich for my pocket book, bit of gash steel and a couple of hours on the lathe, it's a crude thing at best, but then so am I. Worked fine.

I priced the parts up at Motobins in the UK BTW, would have saved a bit , though not so much cos freight is high on such heavy stuff, and I didn't think it worth the wait.

All the bits that came off went back on without arguing (very unusual that for German parts) , and everything worked once it was back together. Including the ABS which i was very worried about.

Couple of hundred kilometres on it now, no leaks, bits come off, noises or other BadThings. And the clutch is now full of clutchy goodness. Very slight judder, but i'll put that down to bedding in. The gearchange seems a lot smoother too, might be because the clutch is taking up earlier, but probably just imagination. Clutch action is definately lighter. Maybe the greasing of the linkage arm, or maybe cos I left off the stupid linkage that is supposed to pull the side stand up when you pull in the clutch. I've no time for such idiot features.

Just need to do a recheck on nuts and bolts being tight, and I'll say the mystery is explained.

Oh, and I've blocked that drain hole up with a wodge of foam. Should still let any oil or water drip out, but prevent the ingress of foreign bodies.

[Motu]

I wonder how they make brake and clutch lining material? Like do they have a big pot of the brew,is it turned widershins with three eyes of newt? Often we find bits of hard material imbeded in disc pads (said newt eye?) and of course these days it's our fault.But because dry clutches last longer than brakes and are not a component you can have a quick look at (unless you pop your box out after work for a quick spline lube) all sorts of mayhem can go on un noticed.After doing many car clutches over the years I've seen just about everything - most just wear out to various points of failure,but some in exact same conditions can show heavy grooving.It must be caused by either soft parts in flywheel and pressure plates or hard spots in the lining material,hard spots in the lining material is the obvious choice.It's a random event,but I've never heard of it causing clutch slip.I've picked some pretty big chunks out of disc pads,no reason why they wouldn't be in a clutch plate.

[Blackbird]

Fascinating account Ixion and glad that it seems to have paid off. I'm glad that I didn't read this when I had my K100RS. I owned it for 8 years and never went near the clutch or actuating mechanism. Other than the known intermittent instrument housing electrical problem which I eventually fixed and some slight cracks in the rear disk (another known problem), it just ran and ran. (Oh, and the 3 months it took me to discover that petrol lead substitute additive was blocking the tank filter, but that's another story).

[Ixion]

It's possible that it could have been a hard inclusion in the friction material that worked loose. The gouging didn't run the full way round the plate, and wasnt in neat annular grooves. It looked like someone had taken to the plate with a screwdriver and dug bits of lining out of the plate.

I've seen annular grooves in clutches many times - this was quite different. There was no grooving or damage to the pressure plate at all, apart from the slight distortion of the mounting tabs.

I've also known a clutch clip when a bit of lining got ripped loose and turned back on itself , which I guess is a similar thing.

Certainly something hard seems to have gotten between the plates at one point in the past, and then been eliminated. (Though that would not have caused the slight "normal" slip, that was just wear)

[merv]

Geez hearing about the stones inside the bell housing makes me glad my bikes all have wet clutches safely tucked away from the elements.

Closest I've suffered to that story is we had a 1981 Honda Accord from new way back then and it had a bad habit of picking up those kinds of stones on fresh seal etc and getting them stuck between the front brake discs and the backplate cover and then they'd grind away and make a godawful noise until you got them out.

[Blackbird]

Closest I've suffered to that story is we had a 1981 Honda Accord from new way back then and it had a bad habit of picking up those kinds of stones on fresh seal etc and getting them stuck between the front brake discs and the backplate cover and then they'd grind away and make a godawful noise until you got them out.

My wife's MX 5 does that all the time. Stopping and reversing for a few metres works on most, but not all occasions.