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Thread: Exploding Driveshaft! '87 K75S

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  1. #1
    3 Red Bricks
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    Exploding Driveshaft! '87 K75S

    I realize that my K75S has the torque of a Pro Stock dragster and the 130/90-17 BT45V rear tire has traction approaching a wrinkle wall slick, but I never thought it could EXPLODE a driveshaft!

    shaft 1.jpg


    LONG MAY YOUR BRICK FLY!

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    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  2. #2
    3 Red Bricks
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    The shaft is the newer style larger universal unit that was used (mileage unknown) when I put it in my bike 40,000 miles ago.

    It has been lubed religiously every 3-5000 miles (grease has been cleaned off prior to picture. There was plenty.)

    The splines on both the shaft and the final drive are still almost perfect except for the wear from after the explosion (I thought I had missed a shift, so I tried several other gears).

    Has anyone ever heard of this happening? Does anyone have a clue what might have caused it?



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    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  3. #3
    Motomark motomark's Avatar
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    Lee
    When you had lubed the driveshaft prior to this problem,what method did you use to pull the drive shaft free from the output of the transmission?I myself had used of vicegrip pliers with much success to remove the driveshaft.Now I wonder if gripping the end of the driveshaft in that manner could possibly have such a outcome.Just a thought.
    Mark

    1971 R75/5,1990 K75RT,1994 K75,1999 KLR

  4. #4
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    I was thinking the same thing. I had been using a pair of 16" ChannelLocks. I only remove the shaft every second or third time. It's been about 8,000 miles since the shaft was removed when I replaced the clutch because of the O-ring leakage.

    I have since made a collar to remove the shaft that would not put a deforming load on the shaft:

    After I made the collar, I realized that using a simple hose clamp and prying on the screw section might work as well.



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    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  5. #5
    Benchwrenching PGlaves's Avatar
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    I have never seen this type of failure, ever. Lee (and Voni too) do seem to explore the fringes of failure modes.

    I too have used pliers to remove the shaft. I'll rethink that now. But those spline teeth are hardened and hardened if not done perfectly means brittle. I think it was an ordinary run of the mill metalurgy flaw that caused it. But, short of sending the pieces to a lab to test for embrittlement that is just a guess.

    I do like the clamp I see in the picture.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  6. #6
    A bozo on the bus deilenberger's Avatar
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    Hi Lee,

    Sure is an odd one. It almost looks as if the metal has crystallized where the cracks are. If I remember some of my old material science courses, this might have been caused by improper heat treatment, or cooling of the shaft after making the shaft. The metal is showing some rather distinctive patterns, and if you look at it carefully - the material composition appears to change with the depth from the surface. If you know anyone in a metallurgical lab in a college, bet'cha they'd know right away what happened - might be worth sending a few detailed photos.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

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