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  1. #1

    GTX 787 top end problems

    Ok guys here we go.
    I have a Ď97 GTX w/ 787cc motor. My daughter ran it full bore over ten miles and one cylinder (PTO) lost compression. I found the top rings went and ended up on top of the cylinder. The dome is pitted but Iíve seen a lot worse. The bore is still clean. Iíve pulled both cylinders and they still look good no noticeable scaring I ran a hone and both cylinders look good. I went to pull the pistons and of course lost a few needle bearings through a cloth that was covering the case. I used an extendable magnet and brought up a few that had went down. I was planning on flushing the case anyway so I did that twice. After counting the bearings I have 33 per piston. I looked at the manual, and I believe there should be 34 per piston. Iím not the original owner of the machine so I do not know if this is from a former redo. I flushed the case again just to see if something else would fall out. I do not believe there is any place a needle bearing can go to get around the cam bearings. The crank spins freely by hand. The starter is still installed on the case and it is presently set up so I can suspended the case upside down by the motor mount plates. That is why Iím asking you motor experts here. Ö..What do you think?


  2. #2
    Besides finding that extra needle bearing, you need to rebuild both carbs and replace grey fuel lines if they are still being used. Clean fuel filter bowl and screen and fuel selector while you are at it or you will just have them same problems again.

  3. #3
    96XPSS's Avatar
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    Look on top the legible piston and see if there is a 81.89 or 82.14 number. The smaller is the original, larger is once-over OEMs. No numbers are larger bore aftermarket pistons.

    I think it's 34 needles too, been a long time since I used stock bearings. Although they are supposed to be the most reliable.

    Welcome to GH!

  4. #4
    It has the 81.89 piston so it is still original bore.
    The fuel system had already been switched to new fuel lines.
    Anybody else on ideas?

  5. #5
    96XPSS's Avatar
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    It was probably water ingestion, from a failed gasket. Running wot, for a long period of time, under max water pressure, is the most probabale. Without pics...that's my guess. I'd replace the exhaust manifold gasket, and headpipe gasket, when you reassemble. If it's never been apart, the original gaskets would dry and shrink for sure.

    Get your cylinders miced by a local machine shop, and see if they are egg-shaped or worn to the point of needing first-over pistons.

  6. #6
    I was going to confirm everything was cool with the cylinders using the shop I am getting my wiseco pistons from.
    "Get your cylinders miced by a local machine shop, and see if they are egg-shaped or worn to the point of needing first-over pistons."

    If somebody is tearing down one of these blocks can you please count the needle bearings for me on one cylinder.

  7. #7
    1997_Seadoo_ShopManual
    States - 34 rollers per cylinder
    So now I've gotta sweep and hopefully find the missing 2
    .....ouch!!!!

  8. #8
    Since the last post I have split the crank no needle bearings in case. I've aquired a few specialty tools and sealants and will be rebuilding the motor from the ground up.

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