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Discussion Starter #1
I have the bike stripped down now and the clutch is out (except for the clutch housing as I still need to make a tool for that). It only took me 3 days but with a lot of re-reading, picture taking and otherwise not turning wrenches time in the garage.

The clutch doesn't look contaminated, nothing leaked into the clutch.
The only 2 seals that were leaking were the one that goes into the slave cylinder pushroad (there was some transmission oil under the slave cylinder)


and output transmission seal (there was some oil in the swingarm).


And, the friction plate is still above the service limit -- 5.4mm (service limit is 4.5mm).

So the question are -- why did it slip and what should I replace? The surfaces on the cover plate and pressure plate look worn but smooth. Looks like there is some heat discoloring, but I don't know if that is abnormal and indicates need for replacement by itself. The plates(cover/pressure) surfaces are very smooth to the touch, but have some "polished" spots.



The friction plate is worn differently on different sides:
side 1:


Side 2:


What does it tell you?

Anyway, the clymer said that another reason the clutch can slip is weakness of the spring plate. I don't know how to test it, but I guess I need to replace it just in case.

The most important question for me now is -- should I replace the pressure plate and the cover plate? Opinions? Experiences?

TIA.

Max
more pics are here -> http://nedod.fomac.net/other/k12gt/clutch/
 

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My clutch came out with even wear both sides so I'm trying to guess at your problem.

I can't think how a clutch could have got that bad without you feeling or noticing something sooner. Do you hold in the clutch a lot at stops?

The clutch disc should be fully floating both sides when it releases and when engaged the spring tension is shared both sides.

I can only think that if you get oil or clutch fluid contamination on one side, that will slip and wear more than the other.

The only other possibility is the plate splines have been jamming on the shaft which would stop it floating so it remains locked up against one side with no wear and wears down on the other. I think I'd have a good look at the splines on the shaft and plate, then check the plate can slide easily.

The heat blueing is to be expected if the clutch has been slipping badly. It's pretty difficult to determine off the bike if the springs are now soft or the pressure plates are out of true.

How can the plate be OK to the service limit if one side is worn down to the rivets? I think the service limit assumes even wear both sides and you have a very unusual problem I have never seen.



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.............PS what are all those red/brown streaks on the friction material?

Has the bike been for a swim in (salt?) water?

Most friction material is impregnated with metal, usually copper/brass but sometimes steel. If the material is left in contact with another metal surface and allowed to get wet, the metal impregnation literally rusts and glues itself to the other surface of a rusted rotor or drum.

This happens frequently on cars when left standing a long time with the hand brake on, the car appears totally locked up when moved, there's a loud 'crack' from the rear, a chunk of disc or shoe friction material is ripped off and there's a grinding noise every time the brakes are used.



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Oh La La!!! Ugly looking clutch.....looks like it had been cooking for a while. You can sometimes clean the blue spots with sanding and wire brushing, but that one looks past that stage.But the pressure plate, that happened on my GS, clutch was slipping,I replaced the disk only and the next day had to replace the pressure plate, clutch was still slipping.

Could there have been just enough tranny oil seeping down from the seal at the slave to contaminate only one side of the plate....just a tought.

But anyway I did have the same leaky seals as yours and reinstalled new ones at the same depth, bench tested and.....they were still leaking. Because there is no "Seal Depth" posted anywhere I opened up my transmission to sort that out, and I do have some good pics as to why even new ones may leak again soon and where they have to be set not to leak.

Here is one, you can see how close the wear groove is from the lube hole, and it is from a transmission that had been worked on by a "Technician"......... :(

 

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Yes you hit the right point on the wear groove.

All conventional seals aim to get the minimum spring tension to seal whilst giving long life. Most rotary seals eventually wear in a groove, but may still stay sealed for many miles. But swap out the seal and position the new one across the wear groove (or oil hole!) and you have a leak disaster. I also think shaft wear increases with heat cycling on the seals which loose their soft flexibility and harden on the lips.

Sometimes, the only solution is to have the shaft metal sprayed and re-ground. On a bike that's such an expensive pig (sorry elephant) to fix, that's a worthwhile option. The newer style Teflon seals look as though they may not produce a wear groove so easily. But the funny thing is, many rush to recommend them, but if you are starting with groove wear on the shaft they probably won't ever seal. For me, Teflon types are for new or re-conditioned shafts.



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Discussion Starter #6
voxmagna said:
.............PS what are all those red/brown streaks on the friction material?

Has the bike been for a swim in (salt?) water?
lol. Yes, those look like red/brown streaks on the friction material. And no, no swimming except for riding in heavy rain :)

But...
* there was plenty of transmission oil on the other end (clutch slave cylinder end) of the pushrod. If oil was there it could probably get on the plates as well.

* when the clutch started to slip it was slipping only under heavy acceleration. I rode the bike home for another 40 miles after that happened, so some damage (uneven wear on the friction plate) could be done at that point. Although, the clutch felt "weak" when rolling from a stop for a month before that.

* the bike was sitting for 2 months before I got around to disassemble the clutch.
 

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Discussion Starter #7
H96669 said:
looks like it had been cooking for a while. You can sometimes clean the blue spots with sanding and wire brushing, but that one looks past that stage.But the pressure plate, that happened on my GS, clutch was slipping,I replaced the disk only and the next day had to replace the pressure plate, clutch was still slipping.
All right. I made up my mind. I am replacing all those parts. BTW, the pressure plate part number has changed
http://www.realoem.com/bmw/showparts.do?model=0544&mospid=48865&btnr=21_0073&hg=21&fg=05

H96669 said:
But anyway I did have the same leaky seals as yours and reinstalled new ones at the same depth, bench tested and.....they were still leaking. Because there is no "Seal Depth" posted anywhere I opened up my transmission to sort that out, and I do have some good pics as to why even new ones may leak again soon and where they have to be set not to leak.
Oh my... I see transmission work in my future. Thanks for pointing it out. How did you bench tested the seal, BTW?
 

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Discussion Starter #8
BTW, for some reason, I couldn't take the pushrod out when I took the slave cylinder off. It just wouldn't come out no matter how I pulled. I thought it should have just slide out easily. :confused:


Another question, I have about installing new pressure plates with old clutch housing. The clymer tells you that those 3 parts are a balanced unit, but then they tell you that when replacing the parts, rotate them 120 deg in relation to manufacturing marks. How does that make the unit balanced and prevents vibration? ... confused...
 

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I'm afraid you might have passed the point of no return like I did and now can't put it back exactly as it came out. I never found these mysterious paint marks they talk about and ended up making a static balance test rig so I at least didn't get any out of balance all on one side. But then you are buying a lot of new clutch parts, so I'm curious about what you do about balance. For the record I found the new disc was well balanced (obvious I suppose) and the other parts weren't far out.

Phasing the drive lines correctly is probably a more important thing to get right. The clutch parts do have drillings in them so I conluded some balancing is already done.

Now the pushrod jamming is bad news and a possible symptom of some of your problems. The pushrod has plenty of clearance in the long bore, from memory there's at least +- 0.5mm which is why mine rattles about unless the clutch is pulled. If the pushrod jams then it can stop the clutch closing fully so you get accelerated wear. I'm not sure what comes first, heat from other problems, oil bunging up the pushrod and seizing or what. But a siezed pushrod is a clutch slave bearing and clutch plate doom with all the slippage signs. That's why I put up with the rattle which is probably what the BMW felt mod. is supposed to stop. Although many think it's to hold back leaking oil.

I know this is my rattle because I wrapped some ptfe tape around the pushrod and for the first 1K miles, clutch rattle was silent.

When you eventually get the pushrod out, roll it on a sheet of glass and check it is true. I hope you haven't got a bent shaft or bent it getting to the clutch. It's tempting when you are up to your eyes in oil and lifting gear to pull the lump rearwards and have it rest on the pilot spigot. Again from memory the rod is about 8mm dia in a 9mm hole. Should be plenty of clearance - but then it's a long hole so any warping is unacceptable.

Keep up the good work and leave nothing to chance now you know how much work is involved.



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Discussion Starter #10
voxmagna said:
That's why I put up with the rattle which is probably what the BMW felt mod. is supposed to stop. Although many think it's to hold back leaking oil.
I took the transmission out with the pushroad still in, so it was probably sticking in the clutch. It doesn't look bent and it already has felt on it filled with oil from the seal leak. I am getting another rod anyway since I can't trust this one.

voxmagna said:
Keep up the good work and leave nothing to chance now you know how much work is involved.
Thanks. I'll try. Although, I totally expect something left to chance due to limits of my experience and knowledge. One thing is for sure... it's good to have a spare bike :D
 

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I've worked on and owned enough street hot rods(cars) to tell you right away that weather or not you found oil, that streaking color and blue (heat) from spinning, is caused by oil from somewhere. I would put new seals anywhere the oil could come from and get a new disc and pressure plate. That oil is cooked into the parts. :( :wtf: :(
 

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Bench testing the tranny....I just filled it with oil and laid it on its end, the seals leaked pretty quick.... :( What I can tell you, after careful measuring as not to hit the wear groove or lube hole, is that the seals were finally installed flush with the case for the output and flush with the "ridge" at the slave. One of them was slightly different from the original so maybe the lip was also offset differently. Vox mentioned Teflon seals, so that may be it. In any case 10,000 Kms and no more leaks. :teeth

I have seen a few posts on other forums where the output seal did leak again shortly after replacement, so that extra little tap to set them in is most probably.....not required considering how close from the lube hole the OEM Seals are set.

I am surprised the tranny came out with the pushrod still in place....any problem with the small bearing/piston on the slave? But make sure you push some grease in the bearing, the one I got from Beemer Boneyard did not have much lube inside.

Lining up the clutch parts shouldn`t be a problem, the new ones are always marked, but I assume you are not replacing the carrier so look for a whitish mark halfway between the center and the outside, should be 1/2" square or so, once you get that one the others will be easy to set at 120 degree. :thumb:
 

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When I put seals in my RT tranny, the seals left the wear-rings much as in your photos.

What bothered me more was the BMW shaft was not smooth at all. It had a rough texture like 1000 grit wet/dry sandpaper. I took a polishing wheel and compound to the shafts to clean them up and minimize the wear ring left by the seal. No sense chewing up a new seal on that rough surface. They were like a mirror when I got done and I smeared some Honda Moly paste 60 on them for good measure.

There used to be some large seal company in Tennessee (I think) that supplied a better grade and higher temp. Viton seal set for the BMW tranny. They cross-referenced off the BMW seals in my tranny. They had a odd brown-red color compared the the stock black BMW seals (which are very poor quality for a high-heat environment like above a hot catalytic converter. What was BMW thinking to save maybe $2 for a better longer-lasting set of seals?


Mack
 

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Razel said:
Since you have it apart, replace the seals if you were considering one way or another. It's about an extra hour's time, and $12.00 for the seals (two for the engine, one for the tranny, IIRC).
They don't look that cheap to me. I priced them at maxbmwmotorcycles.com
https://spreadsheets.google.com/ccc?key=0AqWv2dkNNPVbdEFJVjIxUWVpWFN3UERaVFlvSV9SNEE&hl=en

Also, the parts diagram has 5 seals listed, 2 of which have same id on the diagram as other seals but different part number :wtf:
 

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MIK said:
can you dig more info about it? The OEM BMW seals are not cheap, so I'd rather pay extra and replace them with high(er) quality ones. So far I have to spend close to $100 on the seals only :dunno:

https://spreadsheets.google.com/ccc?key=0AqWv2dkNNPVbdEFJVjIxUWVpWFN3UERaVFlvSV9SNEE&hl=en
Might have been these guys in Vermont (not TN). Harwal Oil Seals Too long ago for me to chase down the receipts since I got rid of that bike for the GT. I did keep the old seals (for whatever reason) until I got rid of the bike and finally pitched them out too.

I'd call them and tell them what you are doing and see if they have something better than the stock seals from BMW and if they will recommend something that will last longer than the BMW stockers which only lasted about 6 years or so on my RT when 3 of 5 in the box failed and leaked. I see from your http parts links they show the seal dimensions in the chart and Harwal lists Nitrile (ugh! only 248 degrees.) or Viton (better at 392 degrees) for them. You need to create an account or call them for prices though.

Man, BMW sure has jacked their seal prices up since I looked in 2003. I thought $5 per Nitrile seal was high back then! Interesting they show one in your list as Teflon (wow, up to 450 degrees!). Didn't have those back then so maybe they are finally getting with the program - I hope.

Have fun!


Mack
 

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MIK said:
Also, the parts diagram has 5 seals listed, 2 of which have same id on the diagram as other seals but different part number :wtf:
5 seals, tranny input,shifter,gear indicator,tranny output and slave, but both the tranny output and slave seal are called " shaft seals". There should be some numbers on the OEM seals to help you figure out which ones you need.
 

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The fact that you found oil in the slave cylinder area means that the seal at the back of the input shaft is leaking. This allows oil to go up the pushrod and onto the clutch. The periphery of the plate is evidence of this. The pushrod felt is a last-ditch method of oil control. Interestingly, it is the same part used on '70-'80 twins.
 

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Some components like the rear drive and I think the tranny can be temporarily sealed air tight then pumped up with a cycle pump to a couple of pound pressure. Then you rotate the shafts and look for oil. Can't do this with the main engine seals though.

Nice way to get the seal lips forming around the shafts.

I've always dipped oil seals (non-Teflon type) in boiling water before fitting. Some of these oem stock seals could have been made years ago and the rubber polymers harden with storage. That's why I prefer sourcing alternatives from a seal supplier with faster moving stock - unless the oem is of special construction.



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