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  1. #1

    What Causes This Failure?

    96 SLT 780, about 30 hours ago this piston was replaced with a used OEM due to a broken skirt near the exhaust side. It was determined there was a crack in the water jacket near the exhaust port. The new failure is similar, but on the other side. Whats the most likely cause of this? I was tuning the ski earlier, turning about 6510-6520 RPM, failure occurred at WOT. Mag and PTO were running around 150-152ºF at WOT, CEN at 148-150.

    Crank appears to be fine, jug was broken at the bottom, head slightly dinged, spark plug shorted. I tossed another piston/jug/head on it, cleaned out the crankcase, and it appears to be fine on the trailer.

  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Perhaps the connecting rod is warped, bent, twisted or out of spec in some manner

  3. #3
    The crank, piston, and jug were replaced with used OEM about 30 hours ago. I did notice that the replacement crank didn't turn perfectly smooth on the lower end PTO bearing, but thats probably not related as it felt fine now that its had some use.

    Is it safe to say this is not fuel related? Think it might have just been the piston or wrist pin were fatigued enough to fail under normal use, and it's nothing to look into further? I don't suspect it was running lean.

  4. #4
    I like pipes. I love boost Mr. GP1800's Avatar
    Join Date
    Jun 2010
    Milwaukee WI
    Excessive piston to cylinder clearance?????

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