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Thread: final drive disassembly?

  1. #1
    BMWNUT grw's Avatar
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    final drive disassembly?

    Are there any resources for someone wanting to disassemble the K-bike final drive to free the pinion shaft for a rebuild? Thinking it would be easier and cheaper to ship the shaft rather than the entire assembly. This is for an '85.

    Am I nuts?
    ----------------------
    Gary Wasserman
    MOA#38120 DoD#0216 Airheads#12166 BMWRO
    '85 K100 (RIP), '08 R1200R (RIP), '82 R100S (was an RT)

  2. #2
    The most challenging thing you'll need is a threaded ring tool. This is a BMW special tool. The threaded ring retains the front bearing and thus the pinion. I understand a tool for disassembling some 4-wheel drive hubs will fit, but I have not confirmed this.

  3. #3
    BMWNUT grw's Avatar
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    Quote Originally Posted by lostboy View Post
    The most challenging thing you'll need is a threaded ring tool. This is a BMW special tool. The threaded ring retains the front bearing and thus the pinion. I understand a tool for disassembling some 4-wheel drive hubs will fit, but I have not confirmed this.
    It's hard to tell from the assembly diagrams in the aftermarket shop manuals exactly what all the parts are. I'd have to have a bad unit to disassemble to really get a good mental image. In this case the shop manuals basically say, "leave it to your dealer."

    I'm sure the original BMW shop manuals have a procedure in them but I've never seen the "official" BMW books.

    My guess is I could bring the unit to my local shop and have them disassemble it but by the time I pay them $100/hour it would be cheaper to send the entire unit and let the machine shop do the disassembly and reassembly work.

    -Gary
    ----------------------
    Gary Wasserman
    MOA#38120 DoD#0216 Airheads#12166 BMWRO
    '85 K100 (RIP), '08 R1200R (RIP), '82 R100S (was an RT)

  4. #4
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    If you are having the splines rebuilt on the input shaft I believe Bruno's wants the whole final drive. That way they can warranty their work easier Vs some one asembling the drive with the incorrect gear lash or bearing preload causing the drive to fail.

    Roy
    Roy G.
    85 K100RT Ol Ruby "Gone but not forgotten"
    02 K1200LTC Hoss "Wrecked on 9/21/14"
    12 R1200RT

  5. #5
    Getting it apart is fairly easy. Big torque on the pinion nut and special wrench for the ring nut or whatever they call it. The problem is putting it back together, shimmed and set up correctly. If you have the tools to take it apart and the special fixtures and tools and an assortment of shims and some machinist's blue to set it up it is one thing but if you don't it will be a problem. For anything other than replacing a seal or O ring - I stay out of there now. It's not worth it to me to be 95% sure I did it right. I want 100%.
    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://web.bigbend.net/~glaves/

  6. #6
    Quote Originally Posted by grw View Post
    Are there any resources for someone wanting to disassemble the K-bike final drive to free the pinion shaft for a rebuild? Thinking it would be easier and cheaper to ship the shaft rather than the entire assembly. This is for an '85.

    Am I nuts?
    Send it to Bruno as a whole unit...he might be able to see some other issue that you might miss when taking it apart.

    Its worth the extra $50 in shipping RT.

    http://www.brunos.us/
    Edde
    93 K75s
    www.motoedde.com

  7. #7
    BMWNUT grw's Avatar
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    Quote Originally Posted by motoedde View Post
    Send it to Bruno as a whole unit...he might be able to see some other issue that you might miss when taking it apart.

    Its worth the extra $50 in shipping RT.

    http://www.brunos.us/
    Thanks to motoedde and Paul for their advice.

    Off to Bruno's it goes. Well, as soon as I get the R80 running better so I can park the K-bike.

    -Gary
    ----------------------
    Gary Wasserman
    MOA#38120 DoD#0216 Airheads#12166 BMWRO
    '85 K100 (RIP), '08 R1200R (RIP), '82 R100S (was an RT)

  8. #8
    This just occurred to me: I've never seen the spline wear out on an '85! Does yours still have the original coarser spline? If so, you might want to make sure that Bruno's has the spline to match.

  9. #9
    Registered User robsara's Avatar
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    Quote Originally Posted by lostboy View Post
    This just occurred to me: I've never seen the spline wear out on an '85! Does yours still have the original coarser spline? If so, you might want to make sure that Bruno's has the spline to match.
    Bruno will probably rebuild the driveshaft and final drive bevel drive with the new many toothed size.

    At least this is how he spells it out on his website.
    Rob R
    1994 K75 My first bike.

  10. #10
    BMWNUT grw's Avatar
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    Quote Originally Posted by Robsara View Post
    Bruno will probably rebuild the driveshaft and final drive bevel drive with the new many toothed size.

    At least this is how he spells it out on his website.
    Yup. That's exactly right. 16 to 20 tooth conversion is part of the job.
    ----------------------
    Gary Wasserman
    MOA#38120 DoD#0216 Airheads#12166 BMWRO
    '85 K100 (RIP), '08 R1200R (RIP), '82 R100S (was an RT)

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