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Shovel head mainshaft

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  • Shovel head mainshaft

    I am having trouble getting the primary set up on a shovel, and would appreciate if anybody has some insight into this.
    I have a 66 FLH frame on the bench. It has a 73 motor, 4 speed box and a 70-78 primary.
    The transmission case is an STD aftermarket. Motor and inner primary are OEM.

    My issue is the clutch hub runs too close to the middle of the bike and makes the belt rub against the sharp edges of the starter gear.

    I fitted an aftermarket inner primary when the bike was reassembled after a paint job, and motor/transmission rebuild. The bike ran fine for many miles until it was worn out.

    To get the primary to work, I have to grind off the inner lip where the inner primary bearing seats against. The primary pullies are lined up parrallel, but offset by about 1/4". The belt was destroyed in quick time. I got the bike back and have been trying to figure out where this offset is coming from. I sourced an OEM inner primary, early one without the stregthening ribs. When I present this to the gearbox, the clutch hub rubs on the inner bearing boss, the same as the aftermarket one.
    The mainshaft is the correct one for this system, 12.470" long.
    It looks like the shaft needs to be 1/2" longer, but not as long as the rear belt mainshaft.

    The only conclusion I have left is that the STD transmission case doesn't set the mainshaft out far enough. It may be this case is for a 67-69 electric start generator motor, but I don't have any measurements to compare it against.
    I have no faith or knowledge that this STD case is the one from the bike before the rebuild.
    Is it possible this is a rear belt drive case with a rear chain mainshaft and inner primary?

    Has anybody come across this before?
    Cheers

    20200106_104535.jpg
    Orange mark is the back of the clutch hub.
    Last edited by aumick10; 01-06-2020, 02:43 PM. Reason: Add belt drive question

  • #2
    It looks like you have a '65-'69 mainshaft which is shorter than what is needed for lining up with a '73 engine. You need a '70 up mainshaft to work.
    Robbie Knight Amca #2736

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    • #3
      Robbie,
      If was only that easy.
      I have measured the mainshaft twice and it is 12.470" long. The correct shaft for the 70 up transmission.
      The gap from the inner primary to the high gear looks bigger than I remember.

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      • #4
        Do you have a clutch hub for an early model? The back is different for E-start bikes.
        Robbie Knight Amca #2736

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        • #5
          I wasn't aware there was a difference. The pt no shows the same part for all 41 and up.

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          • #6
            The electric start hub does not have an extended taper on the back, it is flush. Part #s often do not reflect running changes if the new version will still fit older models, which in this case it will.
            Robbie Knight Amca #2736

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            • #7
              I think this is the correct clutch hub.
              20200107_084530.jpg

              It is hard to see in this photo, but I think this is where my problem is. It has been a while since I have done any 4 speed work, but I thought this gap was much less between the high gear and inner primary.
              4 Speed shaft.jpg

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