I'm Kinda Glad They Use Cheap Steel in These Kits

Discussion in 'Motorized Bicycle General Discussion' started by rohmell, Oct 20, 2011.

  1. rohmell

    rohmell Active Member

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    I had a MB come to me today for repair.
    It seems that the owner did some cleaning and lubing of his centrifugal clutch, and when he went to re-install it, he broke the mounting bolt off flush inside of the crankshaft.
    The owner was all upset, thinking that he now needs a new engine, or at least a new crankshaft.
    I unmounted the engine, center punched a pilot hole and went in with a small drill bit on the drill press. I was amazed how easily that bit drilled thru the broken bolt. Nice, low quality steel, I guess. Did that twice more with progressively larger bits and then went in with a screw extractor. A few taps and the thing un-threaded no problem.
    The broken piece of bolt had all messed up threads on it
    Sent an M8X1.0 tap into the hole and chased and cleaned up the threads, good as new.

    It seems that the centrifugal clutch removal tool with the fat end went into the first few threads on the crankshaft and messed them up, so when the guy went to reinstall the clutch, the bolt became cross threaded and snapped inside the crankshaft.

    Re-installed everything, put a new bolt onto the centrifugal clutch, and sent the guy on his way very happy.

    EDIT: Not glad that the guy had a problem, but glad that the cheap steel made it a breeze to fix everything back to normal.

    So if you can, always use the clutch extractor tool with the skinny end, or else machine your fat ended tool into a skinny.
     
    #1 rohmell, Oct 20, 2011
    Last edited: Oct 20, 2011
  2. Dan

    Dan Staff
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    Purty cool Rohmell.
     
  3. bandito

    bandito New Member

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    Did you remove the c/s to do it? Great save, some times you win and most times MURPHY gets ya.
     
  4. rohmell

    rohmell Active Member

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    No, I put the whole engine on its side on the drill press. I put a piece of rope into the spark plug hole to keep the crankshaft from turning.
     
  5. bandito

    bandito New Member

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    Rope in a spark plug hole?...........Original, WELL DONE!
     
  6. happyvalley

    happyvalley New Member

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    If it wasn't cheap steel it probably wouldn't have broken, lol.
     
  7. GearNut

    GearNut Active Member

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    Well done rohmell!
    I always put a penny or some sort of sacrificial metal between a tension bolt on any puller and the part that is receiving the tension applied. It prevents this exact damage from occurring in the first place.
     

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