A weird final drive situation

Discussion in 'Airheads' started by Mista Vern, Jul 12, 2012.

  1. Mista Vern

    Mista Vern Knows all - tells some.

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    I am refurbishing a 79 R100RS and was in the process of changing the final drive from a low ratio sidecar one to a more normal one. All was going well until I found the rear wheel wouldn't turn. Huh?

    Took everything off and checked the final drive and it is just fine, but learned that in some odd cases the castings/nubs inside the hub part of snowflake wheels interfere with the final drive. My friend, Wirespokes, says this occurs once in a while and is due to either an earlier wheel and a later final drive or vice versa.

    Anyhow, anyone else run into this and if so, is there an easy way to figure out how much metal to take off the wheel hub nubs so everything spins as normal, or do I just keep messing with interference marks until things are good?

    Sorry if this isn't clear - kind of an odd problem that doesn't lend itself to proper nouns.
    #1
  2. Beater

    Beater The Bavarian Butcher

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    Just had a bit of a thought ...

    After reading this I think I understand your problem. You are rubbing somewhere in the shaft or bell housing of the swingarm ... right? Does it turn at all?

    If it's the shaft, it will be rubbing on the center of the swingarm ... this can be 'fixed' by shifting the swingarm to the left (as you are sitting on the bike). Moving it just a micron should tell you if that is your problem.

    Secondly, if it's the bell housing that is rubbing the final drive housing then, you will probably have to remove the shaft and taka little meat off the housing. And you can diagnose this one by getting a Sharpie (marker) and putting several lines down the bell housing ... and then doing an install, and trying to turn. if it turns at all, you should be able to see if the bell housing is scratched (marker removed) ...

    Thoughts? Am I way off?
    #2
  3. robtg

    robtg Been here awhile

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    Right side wheel spacer that the seal rides on still there?
    #3
  4. Mista Vern

    Mista Vern Knows all - tells some.

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    It's this, and yep, figured on doing that - was just hoping that some could say, "Yeah, cut 3/8 inch off at a 40 degree angle" or something like that.
    #4
  5. Mista Vern

    Mista Vern Knows all - tells some.

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    I'll double check, but am betting so. Thanks!

    Edit: due to the interference, it's not even getting that far in, but I will check.
    #5
  6. Beater

    Beater The Bavarian Butcher

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    I know this would be tough ... but post some pics. (You can also email them to me, and I'll post).

    The bell housing isn't even slipping into the final drive? Can you tell how much clearing there needs to be? Can you send me an accurate diameter measurement of your bell housing?

    Does anyone know if the '79 bell housing was a little beefier than usual?

    You have a standard length swingarm, right?
    #6
  7. Mista Vern

    Mista Vern Knows all - tells some.

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    The splines mesh so that is fine - they just don't go all the way to where they are supposed to be. The chances of me being able to take pics are slim - I'll just putter away until it all fits. Thanks for your suggestions!
    #7
  8. princess jamaica

    princess jamaica OLD DOG-NEW TRICKS

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    Take 3/8 ths of an inch off at a 40 degree angle....................problem solved:lol3.You knew it all along.
    #8
  9. Mista Vern

    Mista Vern Knows all - tells some.

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    Thanks! :lol3
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  10. AntonLargiader

    AntonLargiader Long timer

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    The service bulletin said, regarding using a finned final drive with an early wheel:
    "Rear wheels with disk brakes manufactured before 1981 have 12 lugs located in the hub. Before mounting the wheel, it is necessary to machine the lugs off."
    #10
  11. boxerboy81

    boxerboy81 Stay Horizontal

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    #11
  12. Mista Vern

    Mista Vern Knows all - tells some.

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    Thanks Anton and boxerboy. Now I pretty much know I am not totally clueless. Since no specs were given I am going to guess that this is a by just getting in there and doing it using a chalk or a grease pencil to see where things are hitting.
    #12
  13. boxerboy81

    boxerboy81 Stay Horizontal

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    I just ground them off so that the whole inner surface was smooth, like a newer wheel. I had that wheel off the bike a few days back...I could've taken a picture then if I'd known.
    #13
  14. Mista Vern

    Mista Vern Knows all - tells some.

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    Thanks again, boxerboy. :1drink
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  15. Smurfen

    Smurfen Airhead Traveller

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    I had that problem with my '79 RT a couple of years ago. I was thinking of grinding/turning the lugs off but didn't do it and put my old FD back again.

    [​IMG]
    1979 FD

    [​IMG]
    1981 FD

    [​IMG]
    1979 wheel
    #15
  16. Rapid_Roy

    Rapid_Roy I'm tired.

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    :eyes
    Damn, I have no solution,. or drive, and that's final.
    #16
  17. Mista Vern

    Mista Vern Knows all - tells some.

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    Borrowed a small angle grinder and cutting wheels from a friend and once it cools off this evening gonna get to work on it. :D
    #17
  18. boxerboy81

    boxerboy81 Stay Horizontal

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    The two different wheels together...

    [​IMG]
    #18
  19. Hedge36

    Hedge36 My e-penis is huge.

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    Jeezus. Way to get your own thread punted to JM.

    :D
    #19