Cleaning the clutch disc

Discussion in 'Airheads' started by headtube, Mar 13, 2018.

  1. headtube

    headtube Been here awhile

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    Just been in the bell housing to replace the RMS. My clutch friction disc is well within spec but looks a bit glazed over. Do you guys recommend using solvents or perhaps sanding the material to clean things up? Anyone ever boiled the disc to get rid of impurities? That's what I did on the old Triumph friction plates to give them a bit more life.
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  2. Wirespokes

    Wirespokes Beemerholics Anonymous

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    The disc wears unevenly - more on the outside than the inside. So take that into account. Be sure to measure the spring, and possibly replace that even if you don't anything else.

    If the disc isn't wet (oily) I'd lightly sand it to remove the glaze. Some guys replace the clutch as a matter of course - you're in there, so why not? I figure it's too easy to replace, so why? If it's still at 6.5mm I'd keep it.

    I have heard that R100 clutches need to be in good shape or they'll slip. I don't know since I'm pretty easy on them. Others have gotten them to slip when I didn't know there was a problem and didn't slip for me.
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  3. headtube

    headtube Been here awhile

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    6.5mm. Is that the spec when new? Mine is 3.5mm at its lowest point. The Clymer manual spec is 2.8mm for my 79 RS. I'm assuming this in minimum. Perhaps I'll just replace it. Also, the diaphragm spring height is 17.3 at its lowest point. Not much wear on the fingers. Looks like I should replace this also.
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  4. Big Bamboo

    Big Bamboo Aircooled & Sunbaked

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  5. headtube

    headtube Been here awhile

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  6. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Wouldn't replacing the friction disc necessitate replacing the pressure plates, too? Seems like the cost would start rapidly ramping up.

    Also, for what it's worth, the few new diaphragm springs I've bought straight from BMW have shown up under spec height. I had a dealer and a local shop both tell me that's how they come.
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  7. bmwrench

    bmwrench Long timer

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    Almost always. The '70-'80 clutch is at its limit with an R100 anyway.
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  8. TwoShoes

    TwoShoes How Many Shoes?

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    I'll stick my neck out there and say that I've used a good bath in Pine Sol for all my clutch parts including the disk to get everything nice and squeaky clean when the wear isn't too bad. I've done this on several bikes and have not run into problems afterwards with slipping.
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  9. Wirespokes

    Wirespokes Beemerholics Anonymous

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    It matters what year your bike is. Clutches are different after 1980, but generally 6mm is new (I gave that to you wrong in my first post) and 4.5mm is worn out. I've kept them at 5.5 or a little less. The trouble is the two plates plus the disc wear together and if you replace just the friction disc, there will be minimal contact. It's wise replacing everything rather than just the disc.
    #9
  10. headtube

    headtube Been here awhile

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    Well, after cleaning/examining the entire clutch pack I've decided to replace the works. Both the pressure plate and pressure ring have significant wear. A ridge/lip has developed on the inside and outside dimensions due to the friction disc.

    TwoShoes... love the PineSol. Cleaned many aluminium parts with it.
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  11. Big Bamboo

    Big Bamboo Aircooled & Sunbaked

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    Now's the time to consider changing the oil pump o-ring and main seal "while you're in there"... :amazon (don't ask me how I know! :D)
    #11
  12. Geezerrv

    Geezerrv Been here awhile

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    Southland Clutch did a very nice job on my buddy's K1200. There wasn't any fiber left on the disc just rivets dangling in the holes. Not sure about shipping for you across the border though. $250 plus shipping to grind both plates and rebuild disc a bit thicker to make stack same height.
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  13. JGT

    JGT Been here awhile

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    Just a comment on my experience with replacing all the clutch components. I did last year (with Motobins parts for a R50/5). I got the "high quality pattern" new pressure ring along with the pressure plate and the clutch disk. I guess that "pattern" means aftermarket. All went together ok but the ridges on the pressure ring were just a bit too high and rubbed on the inside BMW logo on the transmission case (had to grind that down a mm or so). Also this process seemed to have introduced some bad vibration. Not totally sure but I think it was the pressure ring (which is quite heavy) being out of balance at least with respect to the flywheel and other parts. In the end I send the flywheel and the clutch parts to Lindskog Balancing and they did remove some material here and there to get it all balanced. Much better now.

    I know people say that these parts are all balanced individually (supposedly) when they are manufactured. Maybe they are and maybe not. Or they are matched up at the factory and painted with a mark -- but that goes away when you replace the clutch. Some have fine luck just going for it with new components and not worrying about the balance. But it seems I did not.

    If you are a bit obsessive and don't mind paying for the balancing from Lindskog, it is a way to be sure.
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  14. headtube

    headtube Been here awhile

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    As it happens I spoke to a mate that used Southland clutch. He's put 15,000k on a rebuild that they did. He said that it was cost effective and was happy with the outcome. However, according to Southland that rebuild only lasts for 20,000 miles. Then you've got to shell out for a whole new kit anyway. Guess it depends on how far you ride annually. Has anyone on the forum used Southland's rebuild?

    The balance. Hit and miss? Or perhaps most are happy with the new install. Haven't read anything about it relating to a new clutch pack..
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  15. Wirespokes

    Wirespokes Beemerholics Anonymous

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    How can a clutch only last 20K??? That's hard to believe.

    It's a good idea balancing the clutch components any time they come apart. It's not difficult either, easy to do at home.
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  16. bmwrench

    bmwrench Long timer

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    20K is probably a worst case scenario, and if the folks at Southland aren't fairly serious riders, they may think that 20K is a lot of miles.
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  17. headtube

    headtube Been here awhile

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    Reasons for lasting only 20K is Southland machines the existing pressure plates to make them flat again. This is necessary to take away any lips, ridges or gouges. Then they build the friction disc to accommodate the absence of material. They won't take on a project if the pressure plate/s has been reduced beyond 35-40 thou.
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  18. tsADV

    tsADV Been here awhile

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    If they build a custom friction disc, wouldn't that restore the dimensions to "like new"? Or is the 20K limit due to them estimating quicker wear of their friction discs?

    When I lightened a flywheel & pressure ring (="compression ring"), I noticed said wear to the pressure plate & ring of the "old" clutch, which I replaced due to slipping. Thus I thought of getting the six bolt "pillars" milled down e.g. 0.5 mm, to minimise wear problems with the new set-up. In the end it was easier to shim the periphery of the clutch spring (where it sits against the flywheel) for it to take up some of the space on either side of the friction disc. Not done many miles on it yet (winter), but no problems so far.

    Btw, I am commenting on the pre-81 design.
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  19. SculptD

    SculptD Smells like tech

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    The whole kit from Motobins is $400, and if you use one of their off-brand pressure plates, it's only $315. I'd go that way before $250 the Southland way.
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  20. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    I don't want to crap all over a company that is helping support my favorite vintage motorcycles, but I've used them twice and I don't think I will again.. even as cheap as I am.

    The first clutch (friction disc and pressure plates) I had them machine and re-surface failed after only a few thousand miles. The rivets sheared off as I was sitting at a stoplight on the way to work. It was such a violent experience, I thought I had been hit from behind by a car, but there was no one there. I was lucky I didn't fly into the intersection as the clutch was now jammed up. When I took it apart, it was extra sad to see that much good new friction material destroyed due to their faulty rivets.

    They were admirable and actually replaced my clutch components for super cheap.. but that new clutch failed only maybe 8,000 miles later. I hypothesize their splines weren't hardened because they all sheared off... and damaged my transmission input shaft splines, too. This time I was alone in the Sierra mountains and hundreds of miles from home. That was also unpleasant.

    I called them beck to discuss it and they are reasonable but I've decided to go with BMW components from now on.

    Now I have two blown out Southland clutches on the shelf, not even the pressure plates can be saved. I also now have to rebuild a transmission to replace an input shaft. So, any money I was saving is long gone.

    Those are just my experiences. YMMV.
    #20