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  1. #1
    PWCToday.com Is My Home Away From Home SeaDooSource's Avatar
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    Sep 2006

    2 stroke crank balance questions...

    I have a question that has been on my mind for a while now. It concerns the balance of a sea doo 2 stroke crank (any model). I assume from the factory they're designed to be balanced (or close) with oem parts. So if you add aftermarket pistons and/or rods that may be of a different weight than oem, wouldn't that throw off the balance? And if that's the case, how would you correct? I would guess you assemble the crank without the rods then balance it using bob weights the same way you do an automotive crank? Then disassemble and reassemble with the rods. I'm used to 4 stroke race auto engines so need a little enlightenment on 2 stroke design!
    Last edited by SeaDooSource; 01-16-2007 at 03:53 PM.
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  2. #2
    Tech Guru PWCToday.com Is My Home Away From Home Watercraft Magic's Avatar
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    Feb 2004
    Glendora, California

    Re: 2 stroke crank balance questions...

    Well, for starters, balancing any two clyinder upright engine is a crap shoot at best to get them even close to being "balanced" as in what would be normal for a V motor.
    Aftermaket rods and pistons, even very big oversized pistons don't really make a big difference in the balance of these two clyinder 180 degree two strokes, as long as you do not add or take away stroke from the crankshaft.

    I think if you want to do the best you can with a stock stroke motor, you balance the magneto flywheel. You would not beleve how out of balance these are. If you remove the magneto cover and run the motor with a strobe light shineing on the magneto flywheel, you will run for cover. They wobble all over the place. It is downright scary, and no wonder the front main bearings are always rattling after a few hours on the motors.

    It is one of the first things we do when building racing engines for ourselves, and customers who want it done.

    When building strokers, we often add heavy metal to the balancing flywheels on the crankshafts, or use custom made crankshaft flywheels ( aka, porkchops) to help smooth out the motors' balancing.
    Last edited by Watercraft Magic; 01-16-2007 at 04:07 PM.
    email Chris at Watercraft Magic cdofixr1@live.com

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