Clutch Bolts

Discussion in 'Airheads' started by Voltaire, Apr 23, 2012.

  1. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    I had my R90 out on the track the other day and the clutch started slipping.....it ran ok most of the time just pulling away from a hairpin corner it surged :cry
    I could see oil coming out of the drain holes on either side of the starter motor compartment, probably due to my poor modified breather into a catch bottle.
    Pulled the gear box out last night and two of the star washers under the clutch bolts had broken up :huh
    Anyone seen this before? I'm thinking of leaving them out .:ear

    Clutch had slight oil contamination so gave it a clean down with brakekleen as I have a race meet in this weekend and need it back together.
    Going to run a one piece breather hose instead of my two piece pushed together leaky effort.

    cheers
    John
    #1
  2. PaulRS

    PaulRS Dutch fool

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    New bolts and star washers are recommended every time you do clutch work, acc the RTFM.

    As for the oil spill, how thight is the hose fitting in that bottle?
    It needs some room to releave the pressure.

    And keep the oil level at the low side, 1/3 on the dipstick is enough, any more will be pushed out of the breather.

    Paul.
    #2
  3. ericrat

    ericrat Long timer

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    I don't have any problem re-using the 11mm bolts. At one point BMW said 75 ft/lbs, then later they said 90. I split the difference. I don't like the star washers. I don't think they help much at those torques. Use a dab of Loctite if you would like. When they crack and fail it leads to an immediate problem of a bolt that has totally lost its clamping force.

    I don't use washers on the drive shaft bolts either.

    I should modify that to say, I don't have any trouble reusing clutch bolts that I have replaced once. 35 year old ones, well who know who did what to them over the years.

    Good luck!

    Eric
    #3
  4. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    the hose is a push fit into the bottle....might be a factor.
    So run the oil level lowish?
    The bolts are washers were new in Jan, might use loctite on them this time.
    cheers
    #4
  5. bmwrench

    bmwrench Long timer

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    To what spec are you torquing the clutch bolts?
    #5
  6. Beemerguru

    Beemerguru Beemerguru...G/S guy

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    Are you talking about the flywheel bolts or the clutch plate bolts?!?!

    75lbs on the clutch plate bolts will positively break the star washers..Don't have the manuals in front of me but I think around 22-25lbs is the number..maybe as low at 19....along with Locktite. They're supposed to be single use only bolts...if you want to take the chance of saving ten bucks or so and have them back out at speed..your choice.
    #6
  7. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Clutch plate bolts, the ones holding the flywheel on I'd call flywheel bolts :D
    I'll reuse them as they have only done about 3 hours running and at 22 ft/lbs are hardly stressed.
    The star washers were already broken when I removed two of them...what we call in the Data Centre world a User Intervention Save :rofl
    less weight too with 6 less washers.....:freaky
    #7
  8. disston

    disston ShadeTreeExpert

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    What washers? Star or otherwise. I don't have any washers holding the clutch pressure plate on the flywheel of my R90.

    http://realoem.com/bmw/diagrams/j/w/1.png

    We also don't have part #4.

    I did replace the filister head screws #5 last Winter. Boy they fit so much better than the ones somebody else had reused so the twice used ones I replaced were crap. I think it was money well spent.
    #8
  9. supershaft

    supershaft because I can

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    +1 Early clutches have no star washers and for good reason (tapered bolt heads). If it's a later clutch (I wouldn't race without one), the bolts are getting over torqued and it's breaking the washers. The torque value is 16ftlbs. Typically, that value should get torqued with an inch pound torque wrench. Your 1/2 inch 0 to 150ftlb wrench isn't the tool for the job.

    It's going to be interesting seeing how this ends up making sense. :D
    #9
  10. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Oh yes.... to clarify, its a later clutch/flywheel on an early crank. I'm not sure what my 3/8 Warren and Brown click torque wrench goes up to but is not much more than 75 ft/lbs.
    So confirm the torque setting, clean up the threads, drop of locktite, torque it up, reassemble, test, spend weekend racing....:clap, then over winter start on the 1000 cc engine.
    #10
  11. supershaft

    supershaft because I can

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    Those bolts do not need loctite. They need new washers and torqued to 190 INCH pounds. A wrench that goes to 75 foot pounds is not the wrench to use. You have got two bads going on at once. Not knowing the correct torque value AND not having the correct tool for the job. I am just trying to help! :D Good luck!
    #11
  12. pommie john

    pommie john Long timer

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    Sorry to be the prophet of doom, but if the clutch plate has got oily, it's unlikely to work well again. I would replace it and at the same time make sure you have a heavy duty clutch spring. There are two types. heavy duty and standard.
    #12
  13. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Thanks guys, I'll let you know next week how it got on.
    #13
  14. supershaft

    supershaft because I can

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    +1
    #14
  15. disston

    disston ShadeTreeExpert

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    I understand the desire to want to use Locktight here. It has loosened before. But I'm against it. The problem is the lock washers weren't replaced when they should have been. And the incorrect torque was likely used. Put it together correctly with the required parts, new when needed, and no Locktight.

    When putting Locktight on a torqued fastener like this the torque value must be reduced. The wet Locktight acts as a lubricant when being assembled therefore reduced torque value to end up at correct value. The problem is how much. I have done this in a few places, not this example, and don't think you need it here if there are "New" lock washers.

    Fix the oil leak.

    Cleaning the clutch works for me on the street. Don't know much about racing. Did a little of that in my 20's, early 1972.
    #15
  16. ericrat

    ericrat Long timer

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    I had apparently inserted my head someplace dark.
    #16
  17. Beemerguru

    Beemerguru Beemerguru...G/S guy

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    Clutch bolts at 190 inch/lbs? I thought late model clutch pates were 17 inch/lbs - with a star washwer? I can see flywheel bolts that high but clutch plate bolts?

    What am I missing?
    #17
  18. supershaft

    supershaft because I can

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    Early model bolts get 17ftlb. That's 204inpd. Later bolts get 16ftlb. That's 192inpd. That one foot pound difference is critical in this situation since the star washers on the later setup sometimes can't even stand 192 inch pounds without splitting or spreading out. I always have extra star washers in my shop because they sometimes do split or spread out even with the correct torque. If they do, I back it off and start with a new washer since a split or spread washer is going to let the bolt come loose. Just like sump bolts, late model clutch bolts really could use the proper inch pound torque wrench to do the job right.

    Ericrat's bolts came loose because he OVER tightened the bolts and split the star washers which reduced the bolt tension and let them back out. The bolts can take it but the star washers can't.
    #18
  19. Voltaire

    Voltaire Titanium and Ceramic Hipster

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    Yeah Ericrat....next time you come over to New Zealand and over tighten my clutch bolts and break my star washers your in trouble...:rofl
    In the words of Colin Chapman ... 'We wouldn't put a washer underneath the head of a bolt, why.....what are you going to do that for? Why do you want to take the washer around the track?'":clap
    #19
  20. supershaft

    supershaft because I can

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    I have never tried running them without the star washer since I have never had any trouble with the star washer. It might work! I won't be doing the experimenting!
    #20