Crankshaft gasket blown?

Discussion in 'Motorized Bicycle General Discussion' started by DoubleUgly, Apr 19, 2012.

  1. DoubleUgly

    DoubleUgly New Member

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    Any recommendations on what to look for (what symptoms) if I have a blown crankshaft gasket on an 80 cc?
     
  2. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Smoke coming out of the sprocket cover, and/or the mag cover.
     
  3. Al.Fisherman

    Al.Fisherman New Member

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    If you have a blown case gasket, there can be a leak on any one of the 4 seals. Some engines don't have a clutch shaft seals. Which case they can leak by the bearing.

    Oil residue
     
    #3 Al.Fisherman, Apr 19, 2012
    Last edited: Apr 19, 2012
  4. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Crank shaft gasket = seal, yes?
     
  5. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    What's your bike doing DU? ...and what kind of engine you got before we guess any more. ;)
     
    #5 Bikeguy Joe, Apr 19, 2012
    Last edited: Apr 19, 2012
  6. dmb

    dmb Active Member

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    on a ht a bad crank seal will sound fine with the clutch engaged but will have no power at all. if you take the side covers off look for oily exhaust carbon or smoke [joe] most of the time its only one side. dont flood the motor use the petcock it will happen everytime it floods. also check the center case gasket if no seal rupture.
     
    #6 dmb, Apr 19, 2012
    Last edited: Apr 19, 2012
  7. rustycase

    rustycase Gutter Rider

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    If a crankshaft 'seal' is bad, on the mag side, or pinion side, the motor will be difficult to start, and will not idle. The crankcase is part of the intake tract. same tests apply.


    ...if that is what you are referring to...

    Good luck
    rc
     
  8. mapbike

    mapbike Active Member

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    I had a crank seal go bad on the rotor side of an engine and the air leak it created caused the engine to rev as if it was on cruise control because of the lean condition the extra air was causing, it idled very fast and no amount of idle screw adjustment made any difference, that engine ran smoother than ever and made loads of power but was going to be toast very soon if I had not shut her down when I did.

    This was my experience with a bad crank seal.

    Map
     

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