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Thread: u-joint inspection

  1. #1
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    u-joint inspection

    Bike: 1978 R100S. I've been checking and reassembling a project bike. I noted a slight knock from the drive train while turning the rear tire by hand or rolling the bike around in the garage. It's a much louder knock while under power and riding slowly.
    I disassembled the rear drive train up to the tranny. The rear drive and transmission both turn easily and smoothly by hand. The u-joint however seems to have a bit of "notchiness" on one axis. Is this normal or possibly the source of my knock? Any thoughts would be appreciated.
    John Kuhn MOA#83073

    R1100S, R100S, Honda VFR

  2. #2
    ABC,AMA(LIFE),MOA,RA,IBMW MANICMECHANIC's Avatar
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    U-joints are not supposed to knock. Sounds like time for a new driveshaft, or you'll need to remove the old one and get it refurb'd.
    F.O.G.Rider, Rounder #6,
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    BMWRA Wisconsin Region Rep

  3. #3
    Bluenoser
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    If there is any sideways or up and down play in the u joint then it is toast. Sounds like you may need a new one.

    One thing to check is that there is proper clearance for the driveshaft too work up & down. A lot of times people get so intent on centering the swingarm they forget to allow a bit of room for the U joint to work properly. Check and see that it is not the driveshaft hitting the tube. If it is a clearance issue you may have to adjust the swingarm by moving it a little to the left or right to fix this problem.
    1971 R50/5 SWB with R75/6 drivetrain
    2013 DL650

  4. #4
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    Excellent advice. If I adjust the swing arm slightly to the left the knock goes away. The u-joint was rubbing the inside of the swing arm bell opening. Thanks!
    John Kuhn MOA#83073

    R1100S, R100S, Honda VFR

  5. #5
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    what happened with that notchy u-joint you felt? not notchy, or are you planning to ignore it until it blows apart?
    Ride Safe, Ride Lots

  6. #6
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    I sent an email inquiry to Ted Porter to see if they rebuild twin shock airhead u-joints. (They don't as they rarely need it) Ted advises a slight notch in the middle of the u-joints travel range as normal. That's what I have. There is no axial or rotational play. So I'm going to go with it.
    John Kuhn MOA#83073

    R1100S, R100S, Honda VFR

  7. #7
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    gotcha.

    for those in need of a shaft rebuild.. http://www.machineservice.com/
    less costly than Bruno's, and no border issues to deal with.
    Ride Safe, Ride Lots

  8. #8
    Registered User lmo1131's Avatar
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    Or, as recommended by Ted Porter: Henderson Precision, in Big Oak Flat, California.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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