Flywheel removal - crankshaft end play

Discussion in 'Airheads' started by ali eken, Jun 17, 2019.

  1. ali eken

    ali eken n00b

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    Hello everyone,

    I am working on a 1974 R60/6 engine. When I removed the clutch assy I saw some bronze colored metal plate like thing installed between the flywheel and the crankshaft. I blocked the crankshaft and removed the flywheel.
    That metal plate looks like a homemade shim about 0.15 mm thick. Without that shim, with the flywheel bolts hand tight snug, the crankshaft won't turn. The outer thrust washer is undamaged and rests on the pins. During flywheel removal I could see the inner thrust washer through the right cylinder opening and it looks undamaged.

    It seems the flywheel contacts the rear thrust washer without that shim, but since the thrust washers looks ok I am confused. The outer thrust washer measures 2.46-2.50 mm.

    Do you think that the inner thrust washer was damaged but it is not visible or is there any other thing that could affect the crank end play?

    Any suggestion is more than welcome.

    Thanks,
    ali


    shim.jpg thrustwashers.jpg
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  2. ME 109

    ME 109 Long timer Supporter

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    You won't know the condition of the inner thrust washer with the crank in place.
    It could be that an oversize external thrust washer has been installed, and the shim corrects the end play.
    More than one way to skin a cat I spose.
    Measure the thickness of the external thrust washer and see how it compares to available stock sizes, 4 thicknesses I think.
    Subtract the shim thickness from the thrust washer thickness and see how that compares to available sizes.
    If the crank won't turn the thrust washer/s are too thick.

    The thrust washer is the copper/orange colored ring with the four slots and two retaining pin holes. It comes off.

    On your picture showing the 'inner thrust washer', at the very top of that blue arrow is the thrust washer.
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  3. ali eken

    ali eken n00b

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    Thanks for the reply. The external washer measures 2.46-2.50. The thinnest washer available from BMW is 2.483 - 2.53. Therefore the problem is with the internal one which is a bad news I think.

    ali
    #3
  4. ME 109

    ME 109 Long timer Supporter

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    Apologies for not reading your info enough times. :D
    I'd have thought that the thickest internal washer would work with the thinnest external, dunno.
    I haven't heard of a shim in the mix before, but it may be the best solution without pulling the crank out?
    It seems to work.
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  5. PaulRS

    PaulRS Dutch fool

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    You want to get that crank out and measure the inner washer, then get a combo of washers to get to the correct float.

    I think someone in the past fitted a too thick inner washer, didn't get the float he/she wanted, and added a shim iso taking the crank out again.

    Paul.
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  6. Pokie

    Pokie Just plain Pokie.

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    I see the flywheel in the back ground, it's obviously had some work done to it. The holes in the flywheel look funny, like there's been some minor damage there. I would venture to say the flywheel is either from another bike and has been resurfaced (including the mount) or the problem has been on your bike (not with your present crank) and the flywheel was (kind of) corrected. Why I say the problem wasn't with the present crank, is the end of the crank is rather soft and will distort if strained, I don't see any distortion. If the area where the flywheel mounts is "cleaned up", the fit will be tighter, thus the shim. From what I can see in your photos, the thrust washers look ok.

    To get rid of the shim, you either have to have the flywheel thrust washer contact surface, surface ground or the inside thrust washer needs to be reduced or the outside thrust washer needs to be reduced. Personally, I would either put it back together the way you found it or pull the outside thrust washer and see if a thinner one can be had or have the flywheel ground. If this was winter or if the motor was in need of a rebuild, I'd opt for pulling the crank and reducing the inside thrust washer.
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  7. bmwrench

    bmwrench Long timer

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    Don't count on it. I've seen several engines in which there was inadequate crank end-play, even with the thinnest thrust washers. It's interesting that they escaped the factory. I wouldn't use the brass (or bronze) shim again, either. The retention of the flywheel depends partly on the smooth mating surfaces.
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  8. ali eken

    ali eken n00b

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    Thank you for the valuable information Pokie. The following picture is the mating surface on the flywheel.

    flywheel.jpg

    I don't think anyone who worked on this bike took the time and effort to rework this part but there is a good chance that it is not the original flywheel that came with the bike. As you and Paul suggested, I think the right thing to do is to get the crank out and make a stack-up for an end-play within tolerance, however without having the proper tools crank removal is not an easy task for me.

    Can I have the rear(outer) thrust washer ground down to about 2.3 mm?

    Thanks,
    ali
    #8
  9. Pokie

    Pokie Just plain Pokie.

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    You can take the thrust washer to a machine shop to see what they can do with it BUT the face material is different from the base material, making it a bit difficult to work. The base is steel but the face material is a form of either copper or bronze. I'm not sure how thick the softer material is but I don't think it's just plated. The machine shop will have to determine how the cut or grind the soft material. If you are going to pull the crank anyway, I would suggest taking the stripped lower end to a BMW repair facility so they can simply order the correct thrust washers. Probably be cheaper than having a machine shop deal with it.
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  10. Plaka

    Plaka Brevis illi vita est

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    The thrust washer is actually a bearing. It cannot be ground.
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  11. PaulRS

    PaulRS Dutch fool

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    The backside can.

    If you look how that bearing is constructed, it's a steel plate with the bearing material put on in 4 segments.
    Between those segments the base plate is 2 mm thick.

    All you need is finding a shop with a surface grinder with a magnetic table, put the washer with the bearing side down on the magnet and run the grinding stone over the back.

    How much to take off is a guess, the end float should be 0,08-0,15 mm.
    What is the float with that extra shim installed?

    Paul.
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  12. robtg

    robtg Long timer

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    That could done by a competent machinist on a lathe. If the end float is correct with the shim, just reduce the thrust bearing thickness
    by the same amount and toss the shim. Just make sure it doesn't go through the bronze outer layer.
    #12
  13. Disston

    Disston ShadeTreeExpert

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    If you are going to fix it I would buy a new part, shim or bearing, to fix it right.

    I doubt I would waste time matching the shim even if I was the machinist and only wasting my time.
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  14. robtg

    robtg Long timer

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    If the inner thrust bearing and the outer were the thinnest available what would you do?
    I would either machine the flywheel thrust face or the bearing. Putting a shim between the crank and f/wheel
    would be my last choice.
    #14
  15. Plaka

    Plaka Brevis illi vita est

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    if the assembly has been shimmed then the basic parts are too thin. grinding will only make them thinner ( and wipe out the numbers on the back)

    most surface grinders (I daresay all) have magnetic tables.
    #15
  16. ME 109

    ME 109 Long timer Supporter

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    The shim is there because the thrust washers add up to too thick. The shim reduces the thickness of the rear thrust washer, sort of.
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  17. ME 109

    ME 109 Long timer Supporter

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    I've always felt rather chuffed when robtg liked something I wrote. I bet I've made him shake his head at least 10,000 times tho. :D

    What is wrong with a shim in this situation, if a suitable shim material was used?
    I don't think brass is a suitable material.
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  18. PaulRS

    PaulRS Dutch fool

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    A joint bolted together is held by the friction between the bolted parts.
    The tightened bolt put pressure on the joint, this translates to friction, and this friction hold things together.

    That brass? shim reduces that friction, with the change the joint working loose.

    Or so?

    I'd machine the back of the outer shim 0,15 mm and call it good for now. (If the float checkes out ok, that is)

    Come winter I'd pull the crank and do a proper job.

    Paul.
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  19. kcoralj

    kcoralj Been here awhile

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    Dicey cut for a lathe, they've got end float too. I wouldn't attempt to cut it as the pressure is too high and it wouldn't come out flat enough. Grinding is the way to go, maybe with a bit of lapping for the surface finish.
    You've got a size range for the thickness, but the flatness and parallel has to be held much tighter for it to work properly... oil films and such.
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  20. Disston

    Disston ShadeTreeExpert

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    The only reason this engine needs the shim is because the rider/mechanic doesn't have the tools needed to remove the crankshaft. That's really OK with me or machining the thrust bearing too.

    I'm just saying if it was me I would either buy/make/borrow the tools to get the crankshaft out because I am OCD about such stuff. Later, after, I become more expert at these things I'd prolly take short cuts too.

    Short cuts are for people that know what they are doing.
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