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  1. #1

    Seadoo 787 Rebuilt top end, pto cylinder trashed

    Rebuilt my 787 over the past month, took her to the lake this weekend for break in. Everything ran great! Only ran about 30 minutes. Got home pulled the spark plugs, the pto plug is covered in metal flake! WTF!! Pulled the head, of course the bottom ring caught on the skirt and was destroyed, resulting in the cylinder being scored, head trashed, and piston trashe. Mag cylinder and piston is still good as new. My question here is Im running .50 wsm pistons, can I leave the mag piston and put a .75 piston in the pto cylinder?


  2. #2
    SELF27's Avatar
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    Did you remember to cut rave valves back?

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  4. #3
    Yep, they were shaved when I did the rebuild, they have plenty of clearance.

  5. #4
    No one can help me here? Guy at ski shop said it was do able, but I dont wanna put the crank out of balance.

  6. #5

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    much better to go next over size for both cylinders.and buy spare cylinders and 1pc .50 pistons for spare.

  7. #6
    Myself's Avatar
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    The 787 is pretty tough and will do just fine with one piston .25mm (.010) larger than the other. After it was bored were the port edges chamferred? That could catch a ring. The pistons aren't in backwards are they? Easy for a beginner to do an a 787. The only other thing that might cause something like that was a piece of metal from the previous damage that was hiding inside the crankcase and finally came out to play.

  8. #7

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    would that be applicable to stock set ups?or even limited set ups?

  9. #8
    Myself's Avatar
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    I don't like to do that on any engine but you gotta do what you gotta do to ride. I would not do it on anything other than a stock machine.

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