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  1. #1
    EZ Dock of Long Island Shibby1485's Avatar
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    Crank snapped in two at center pin



  2. #2

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    never seen that before,stock crank-was he out jumping wave?

    cd

  3. #3
    ... bad gas

  4. #4
    EZ Dock of Long Island Shibby1485's Avatar
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    out in the ocean when he landed heard a noise and ski stalled...

    it's a GTX DI

    the ski still ran with the broken crank... starter turns the front cylinder and the gear for CB shaft and air compressor pump so the whole injection system would still work and it would fire and run... just really crappy and makes a ruckus running...

    my tech already split the crank apart and rebuilt it and is reassembling the bottom end. waiting for two .25mm over pistons that will be here tomorrow and we'll bore and hone the cylinders and have it back together and done by end of day tomorrow.

  5. #5
    cant believe it did not trash the cases. i think you got lucky sort of

  6. #6
    flyin' the friendly skies airbornexp's Avatar
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    thats very odd. im also very surprised that it did not trash the cases. it doesnt look like a clean break...was this a 787 or 951?

  7. #7
    EZ Dock of Long Island Shibby1485's Avatar
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    951 DI

    we've had a few cranks come through our shop break like this... mostly yamahas in the past tho.... we service over a thousand skis a year, we get to see some good freak failures from time to time. those are the fun ones to work on

    i'm about to post another pic on my FB page for a 1200 yamaha PV engine that physically cut itself into an 800 while it was running... cut the cases in half all the way around

  8. #8
    SURFnTURF's Avatar
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    You might want to check the cases for run out before bolting back together.4 things come to mind 1) crank misalignment,2)cases misaligned,3) wrong size bearings installed between front and rear 4) or could be just metal fatigue.

  9. #9
    EZ Dock of Long Island Shibby1485's Avatar
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    Quote Originally Posted by SURFnTURF View Post
    You might want to check the cases for run out before bolting back together.4 things come to mind 1) crank misalignment,2)cases misaligned,3) wrong size bearings installed between front and rear 4) or could be just metal fatigue.
    Thanks for your input

    We were real careful on inspection and reassembly... but seem to be having a problem, maybe what ultimately caused the failure. The motor is vibrating pretty hard from deep within. you see it, and you feel it through the hull and trailer very very strongly...

    we pulled the motor back out, stripped down inspected everything and put it back in.. still vibrated.

    pulled it back out again... changed out counter balance shafts, changed out flywheels, checked the crank, and put it back together.


    rebuilt Crank is true to within .0015" or better

    new pistons

    2 different CB shafts have been tried

    2 different flywheels have been tried

    Also tried a new MPEM from a perfectly running ski to rule out ignition problems.

    we are using the original cases, cylinders, and head


    ...... i guess it's possible this nasty vibration could be what destroyed the original crank and broke it.


    i have another set of DI cases laying around, about to pull the motor out and swap all the internals into another set of cases... does anyone have any ideas on what we may be overlooking?

    99.9% positive the crank is perfect. we trued it twice, every bearing is perfect. the counterbalance shaft is timed correctly both by the paint marks on it as well as by checking TDC of cylinder to air compressor piston.

    Kinda has us stumped and feel like we've exhausted every possibility to this point except cases.

  10. #10
    WOT 88's Avatar
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    Quote Originally Posted by Shibby1485 View Post
    Thanks for your input

    We were real careful on inspection and reassembly... but seem to be having a problem, maybe what ultimately caused the failure. The motor is vibrating pretty hard from deep within. you see it, and you feel it through the hull and trailer very very strongly...

    we pulled the motor back out, stripped down inspected everything and put it back in.. still vibrated.

    pulled it back out again... changed out counter balance shafts, changed out flywheels, checked the crank, and put it back together.


    rebuilt Crank is true to within .0015" or better

    new pistons

    2 different CB shafts have been tried

    2 different flywheels have been tried

    Also tried a new MPEM from a perfectly running ski to rule out ignition problems.

    we are using the original cases, cylinders, and head


    ...... i guess it's possible this nasty vibration could be what destroyed the original crank and broke it.


    i have another set of DI cases laying around, about to pull the motor out and swap all the internals into another set of cases... does anyone have any ideas on what we may be overlooking?

    99.9% positive the crank is perfect. we trued it twice, every bearing is perfect. the counterbalance shaft is timed correctly both by the paint marks on it as well as by checking TDC of cylinder to air compressor piston.

    Kinda has us stumped and feel like we've exhausted every possibility to this point except cases.

    No possibility of it being caused by something in the driveline? What about some hairline fracture in the cases you may have overlooked? it's possible the cases are flexing when running and throwing the rotating assembly out of balance.

    I may be out in left field but your situation is a bit perplexing at this point, anything could be possible.

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