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  1. #1

    GP800r - inspect crank or replace the darn thing

    I've recently purchases two GP800Rs that were a bit neglected. Apparently they had reman motors put in them, but were either flogged to death or didn't have their carbs rebuilt when the motors were done. Either way - one piston on both skis is trashed.

    I picked the skis up partially disassembled. One has a motor completely out and basically torn down. The other has the top end off.

    I'm considering replacing the motors with longblocks from SBT (yea, the lazy way to do it - but we're probably talking about $1200 motor - $100 carb kits - $50 shim kits - $50 gasket kit + $150 shipping). Skis may or may not need instrument clusters also - as they sat outside and the LCDs have some water in them.

    The question is - can the condition of the cranks and associated bearings be determined... Both turn freely and I don't see any debris or feel any grinding in the cranks. Obviously doing a top end on these skis saves about $700 - so is it reasonable to pull the cranks and have them inspected or is that somewhat of a craps shoot in terms of general crank condition... I don't want to put them together and then have to pull the motors back out in another few hours.

    Any suggestions?


  2. #2
    Subscribing.

  3. #3
    WATER WOODY's Avatar
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    Welcome to GH. The crank is the heart of the motor. Send them out to be checked. It doesnt cost that much to have them inspected.

  4. #4
    Have a recommendation? Appreciate the comment.

    I should note that I have machinists tools - if the procedure is checking run out and variations, I can likely do it... If there is more to it than that, I'm happy to send it out.

  5. #5
    SkiSwede's Avatar
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    As long as the pistons aren't pitted then the crank didn't fail. If the bottom end doesn't need to be rebuilt I wouldn't tear it down. But, you may want to do it to replace the seals. I just spin the bearings, and if they all spin well with no noise and have no evidence of deterioration then they're fine with me.

  6. #6
    Define pitted - I've got a piston that clear had some alumiunum come off of it and did some pretty serious pitting.

    My concern would be that debris get loose in these motors and end up in the crank...

  7. #7
    SkiSwede's Avatar
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    Typically aluminum debris will not significantly pit a piston, but I suppose that depends on our definitions. If a crank bearing fails steel debris can cause serious piston damage, sometimes leaving pieces embedded in the piston top.
    If it looks like the piston lost a lot of material some could have made its way to the crank, but thats not common. If you do tear down the bottom end, spray all the bearings with carb or brake cleaner while spinning them. That will remove any unwanted debris.

  8. #8
    Yes, I had a piston that lost at least 50% of the skirt material. Both the piston top and combustion chamber are pretty beat up. This motor is in much worse shape than motor #2.. Both are remans..

    I appreciate the advice.

  9. #9
    All hail the Chief! fullboogie's Avatar
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    Quote Originally Posted by SkiSwede View Post
    As long as the pistons aren't pitted then the crank didn't fail.
    Says who??? Every single bearing can be bad without pitted pistons.

    To the OP - send 'em out to Crank Works and find out for sure. It's cheap insurance.

  10. #10
    SkiSwede's Avatar
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    Quote Originally Posted by fullboogie View Post
    Says who??? Every single bearing can be bad without pitted pistons.

    To the OP - send 'em out to Crank Works and find out for sure. It's cheap insurance.
    Sorry, what I meant was to the effect that if the piston isn't damaged from bearing material then it likely didn't fail as the result of a bearing. But I know thats not always the case.

    Having the crank inspected is probably the best option, I would just never spend the money on it myself.

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