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Thread: 1976 R90/6 rear end

  1. #1
    Registered User
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    1976 R90/6 rear end

    A sad story. . On my way to the rally in MO. this summer, we were 30 min out of Talihina on the way to Mena, AR when the rear end of my bike shredded itself.

    The bike has been sitting in the garage since and it's time to get things back in working order.

    Does anyone have suggestions about how to fix this one? Should I get the bad unit (now removed) rebuilt, or should I look for a used one? Or just go with a new one.

    Are earlier years a different gear ratio? Could that be fitted?

    Thanks
    Brian
    Last edited by grif_57; 10-15-2012 at 04:39 PM. Reason: Editorial
    1976 R90/6
    Member# 174498

  2. #2
    Rally Rat
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    Shredded

    That's a loaded question without more information! What do you mean by shredded?
    Are the drive splines shot? If that's the case, then you can have the splines rebuilt. Along with that you might as well have it torn down, cleaned and have the seals replaced.
    On the other hand, if the internal gears are damaged, then you're better off replacing it with a good unit with good splines. Plenty of them out there, just look for one with the right gear ratio.
    Boxerbruce

  3. #3
    Registered User lmo1131's Avatar
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    Virtually any final drive from any post 1970 - 1979 airhead will work, it's just a matter of gear ratio.

    edit - they will all fit, it doesn't make any difference, other than acceleration/top speed/indicated speed.

    Personally, I had mine rebuilt by Ted Porter; buying "used" you just never know what you're getting into. That said, Ted's shop can take a while (worth waiting for) so I bought a used FD on eBay and installed it while Ted was rebuilding my FD. I re-sold it when my FD came back.

    There are ten final drives on eBay this morning; 37/11s and 32/10s; $180 - 225 range
    Last edited by Lmo1131; 10-16-2012 at 05:37 PM.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

  4. #4
    Rally Rat
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    Rear Drive

    I posted to you in a private message format. Please reply.
    Boxerbruce

  5. #5
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    Quote Originally Posted by 1074 View Post
    That's a loaded question without more information! What do you mean by shredded?
    Are the drive splines shot? If that's the case, then you can have the splines rebuilt. Along with that you might as well have it torn down, cleaned and have the seals replaced.
    On the other hand, if the internal gears are damaged, then you're better off replacing it with a good unit with good splines. Plenty of them out there, just look for one with the right gear ratio.
    I have the FD off and the drive shaft is fine along with the splines. The rear wheel gear teeth are a little dirty but otherwise fine. I was able to turn the input to the drive unit and no turn on the output, so pretty sure its inside the FD that is bad.
    1976 R90/6
    Member# 174498

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