busted flywheel/sheared shaft with pics

Discussion in 'Motorized Bicycle General Discussion' started by Spunout, Jun 19, 2009.

  1. Spunout

    Spunout MB Builder Extraordinaire

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    tooling down the road at 40mph, i felt the slightest drop in speed just before the motor died."huh?" i noticed black oil coming from one of the bolt holes on the bottom of magneto cover.
    pulled it off and there was the flywheel, wedged into the magneto.
    the flywheel is comprised of three parts. apparently, one of them came off the main center. the shaft wanted to keep spinning and it did. sheared the flywheel right off.
    gonna have to use the ez-out and replace the shaft/flywheel. if this wasnt my race motor, i probably wouldnt try so hard to save it.
     

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    #1 Spunout, Jun 19, 2009
    Last edited: Jun 19, 2009
  2. Forbisher

    Forbisher New Member

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    40mph? What size rear sprocket are you running?
    Shifter kit?

    Flywheel???? It is just a magnet not a flywheel

    and you have sheared the shaft off that is pressed into your crankshaft flywheel

    Ez out??? You need to split the cases and replace the whole crankshaft assembly

    You would have to get one from a used engine

    Might as well use a whole new bottom end or a new engine

     
    #2 Forbisher, Jun 19, 2009
    Last edited: Jun 19, 2009
  3. dvddtz

    dvddtz New Member

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    I found this crank as a spare,just a couple of keystrokes. Motorized Bicycle Engine Kits. usflg All the parts are out there, you just have to look a little. Good luck. David
     
    #3 dvddtz, Jun 19, 2009
    Last edited: Jun 19, 2009
  4. Creative Engineering

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    Spun,

    Unfortunately, Forbisher is right.

    Jim
     
  5. Creative Engineering

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    I think Dax has the crank & rod assemblies too...even though it isn't listed on the parts page.

    Jim
     
  6. Forbisher

    Forbisher New Member

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    Thanks for the link but....
    There is no way that crank and rod will fit a 48 and a so called 80 and
    what motor factory???

    Also the bearing sizes, shaft diameters, keyways vary from factory to factory
    so good luck!
    The magneto side is probably the same but the crank gear side isn't

    As far as I know Grubee does not sell replacement cranks
     
    #6 Forbisher, Jun 19, 2009
    Last edited: Jun 19, 2009
  7. 2door

    2door Moderator
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    Spun,
    You're gonna need a new motor...........and I'd sure like to have that crankshaft seal if you're gonna trash that case. :)
    Tom
     
  8. Norman

    Norman LORD VADER Moderator
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    2Door
    I don't think you want that crank seal look at the oily poo there its been leaking I think. I do not think the leaking seal caused the mag rotor shaft to break but it looks like the seal was leaking.
    Norman
     
  9. Spunout

    Spunout MB Builder Extraordinaire

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    the motor has been ported, handmade intake and large carb from a XR80. running a 36tooth, and top speed is 44mph. thats fast.

    i always called the magnet a flywheel...dunno why.

    oh man, i dont have time to split the case. i thought the shaft screwed in, not pressed. ive never messed with the bottom ends much, just the tops. never needed to.
     
  10. 2door

    2door Moderator
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    Norm,
    You're right. I posted that before we found those other ones. I should get those this week. I'll let you know if they fit.
    Tom
     

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