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  1. #1

    Top end question

    I just picked up a 96 sl780. Front cylinder has hole in piston as I am finding out is a common problem with with this model. My question is, is there anyway to do a top end without pulling the entire engine on this ski?? I took out the gas tank with hopes of unbolting pipe and sliding out, it appears though that there is no way to remove one of the four top exhaust bolts due to hull clearance. Is there anyway to avoid pulling engine, or is that just what has to be done? Thanks in advance


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Holing the MAG piston is NOT common on a 780. A 650 or 750 it is. But they worked out most of the bugs on the 780.

    Something caused that piston to go. You have to remedy that problem, or it will happen all over again.

    Most common cause would be dirty carbs, dirty filters, old hoses, bad petcock, air leak, or misadjusted carb settings

    You can do the top end in the ski. You just have to get creative with removing the exh pipe bolt.

    Try prying the hull side away from the pipe when removing the bolt.

  3. #3
    Thanks for the info. So the inadequate fuel pump is not an issue on the 780? Also, the petcock is not connected, and was in the storage tray when I bought the ski. How can I test it to make sure it's good? I planned on doing the fuel lines, and was going to put a triple pump on, but if you think it's unecessary on the 780, I will hold off on the pump. As for the exhaust bolts, you were much more helpful than the manual which showed way more clearance than on my ski. It also stated that the bolts were 12mm and mine are 19mm. That one really had me scratching my head. Thanks again

  4. #4
    Canadian Beaver Inspector jkindt's Avatar
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    Quote Originally Posted by Anthro441 View Post
    Thanks for the info. So the inadequate fuel pump is not an issue on the 780?
    The stock 780 fuel pump is a Mikuni pentagon-shaped high output triple outlet fuel pump. The earlier skis had a Mikuni round-shaped single outlet fuel pump that was rated at almost half the output of the pentagon-shaped pump. As long as you have the pentagon-shaped pump, you should be fine.....as long as it works properly. A rebuild kit for the pump is cheap insurance!
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  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    RIGHT ^^^^^^^^^

    If you're fuel pump looks like the pentagon shaped one in the above pic, it's fine. May want to rebuild it for cheap insurance as previously mentioned. ($16 for the kit)

    If the petcock was removed by the previous owner, sounds like they had a fuel related problem and was trying to resolve it by bypassing the petcock. Just replace it with a new one. Some Sea Doo valves will swap right out for the stock one you have. The positions may be slightly different, but will work just fine.

    Or you can disassemble the one in the storage bin and inspect it for any rubber swelling/restrictions, or rotted out O ring seals.

    I think you're slightly confused about the bolt sizes. 12mm is the actual thread size, not the socket required to remove it.

    How about posting up some pics so we can see what you're working with?

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