Airhead Gearbox Woes

Discussion in 'Airheads' started by kougan, Feb 18, 2013.

  1. disston

    disston ShadeTreeExpert

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    It may be advisable. But several reliable sources always say to leave it be. I do know it is one expensive bearing. So if there is any tendency to cut corners this is one that few will fault you for. If there is any notice of reason when examined of course at that point you should change it.

    The front bearing on the output shaft is the most failed bearing in the 5 speed. This one has to be changed.

    Do you have the use of a suitable press for changing the bearings?
    #21
  2. Solo Lobo

    Solo Lobo airhead or nothing

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    I've heard it both ways, "it never fails" and "I've seen that one go bad lots of times"....

    And yes, it's one pricey SOB!
    #22
  3. kougan

    kougan Been here awhile

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    Thanks for the tips on these, Solo and Disston.

    I did finally get around to checking out the clutch, and all looks just as it should.

    Conclusion is: the grinding, clattering sound must have been coming from (possibly) all three rear gearshaft bearings rumbling loose against the casing. This must also be why there is black scuffing around the edges of all of them. What I don't know is exactly how they all managed to come loose at the same time. Any thoughts, or has anyone experienced the same thing?

    I'm going to go ahead and replace the five bearings and leave the pricey one alone, as it looks great and spins fine.

    Thanks for all your input. :thumbup
    #23
  4. ME 109

    ME 109 Long timer

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    I would take the cover to someone who can measure the bearing pockets. I still think the bearings have spun in the cover excessively.
    New bearings will spin in the cover as well, if indeed the pockets are flogged out.
    If the bearings can spin in the cover, they will spin on the shims and wear them away.
    Motobins sell new covers, or a s/hand one could be found.

    Of course, I could be completely wrong.
    #24
  5. kougan

    kougan Been here awhile

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    I was thinking the same, although I checked to see if the cover sits loose on the bearings, and it's definitely tight enough to where I'll have to pound it back on with a mallet. (i.e., it's a tight fit between bearings and cover).
    There is a little grease in the cover pocket where the input shaft bearing sits though, that may be due to excess grease seeping in from the throwout bearing/piston. This may have caused that bearing to start spinning.

    I'll see if I can get a correct measurement on the pockets, but I'm betting on just cleaning up the extra grease and putting in the new bearings. We shall see.
    #25
  6. supershaft

    supershaft because I can

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    That cover just looks stained to me. I don't think anything has been spinning there. The five speed front input bearing ALMOST never goes bad. They do all the time in the four speeds so they put a sturdy one in the five speeds. I haven't worked on THAT many four speeds but, so far, every one of them had a bad front input bearing. I rarely see any trouble there in five speeds. I think that must be the source of confusion.
    #26
  7. ME 109

    ME 109 Long timer

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    Hopefully you'll heat the cover to 80-100c first.
    My thoughts.........98% slip on, 2% 'tap' on.
    #27
  8. disston

    disston ShadeTreeExpert

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    Use plenty of heat when replacing the cover. I agree with SS that it is stained for some reason. If those bearings had spun you would see more damage than a darkness.

    The front bearing on the OUTPUT shaft is the first to go on a 5 speed.
    #28