better crank balancing

Discussion in 'Canadian Daves JustKDX' started by jaguar, Jul 23, 2013.

  1. jaguar

    jaguar Subscriber

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    Has anyone drilled holes in their flywheels for better balancing (less vibration)?


     
  2. EYY

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    They should already be balanced? I'd assume something is wrong if you're searching for less vibration?
     
  3. jaguar

    jaguar Subscriber

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    My '89 had too much vibration. I had to put buckshot inside the handlebars to make it livable. It's not the first time a manufacturer let part of the bike design be "close enough". If my next KDX is the same way then when I change out crank seals and bearings I will drill 6mm holes in the flywheels to see what happens. If its made worse then I'll have to take it apart and add more metal to that area instead of take it away. I'll post my results.
     
  4. tirex

    tirex Member
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    When I replaced the main bearings, has less vibration.
    Also you can crank itself has runout exceeds the limit.
     
  5. jaguar

    jaguar Subscriber

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    It vibrated the same after replacing the bearings and although a wobbly crank will cause vibration, I think it is common problem with the KDX since the topic of how to reduce vibration has always been a popular one.
     
  6. EYY

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    Have you looked for other sources of vibration too? The exhaust may be touching the frame somewhere?
     
  7. jaguar

    jaguar Subscriber

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    I'm a fairly good mechanic and know a good deal of 2 stroke technology and I don't think I overlooked any non-crank source of vibration. Like I said, others have experienced the same thing.
     
  8. ridejunky

    ridejunky Pro Class
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    Unless you have a balancer you are taking a crap shoot, the odds of getting it "more balanced" are pretty low. I would get a new fly if you are so sure that is the problem, being a fairly good mechanic, I am sure you already know that as well as the consequences or reducing fly wgt.
     
  9. jaguar

    jaguar Subscriber

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    Since I started this thread I have devised my own method of crank balancing that I perfected on small engines made for bicycles (since replacement cranks are only $25). You can read about it at www.dragonfly75.com/moto/vibes.html
     
  10. jaguar

    jaguar Subscriber

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    I have a new spreadsheet easily used to determine the best balance. It is free to download here: Crank Balance Calculator
     

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