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  1. #1

    yamaha gp1200 problem

    Hi there, im new to jetskiing and got my first problem the other day . Its a yamaha 99 gp1200.

    Engine was rebuilt at a cost of £1600 just before i bought it. Have done around 15 hours since to run it in. This was the first time id been able to open it up. I was going about 50mph and it just cut out dead. i pressed the start button and nothing. i tried to enter immobiliser code but it wasnt needed. tried the start again and it tried to turn once , was like the battery was dead, however i tried again and it tried to turn twice. whilst floating in middle of the river tay, scotland, was calm thank goodness, i checked plugs etc, they were fine. tried again and got it start . first instinct , homeward bound, ( someone was on another ski ), it ran for 20 seconds fine then died again. this happened 8 times till i was back ashore. it sounds like its misfiring too.

    The misfire may be coming from a loose plug cap as it came off the other day but was still running on 2 cylinders before i got back ashore and checked, so i dont think it could be because of this that its done what its doing. i got plugs and caps in the post but hoping someone might know what to try. much appreciated, chris


  2. #2

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    I would pull the head and check cylinders-sounds like you stuck a piston

    cd

  3. #3
    Quote Originally Posted by chip View Post
    I would pull the head and check cylinders-sounds like you stuck a piston

    cd
    Hi there, im no meachanic , far from it, but it does always start and when it starts it runs great for they 20 seconds then dies, the screen for my fuel and oil etc goes off too im sure when it stops, but if i press a button something always comes on the screen.

  4. #4
    Nothing like getting air, while sitting in a chair VonnerNIX's Avatar
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    Sounds like a seizure to me as well. Motor will lock up when it gets hot, and when it cools down it will work again until it gets hot again.

    I would check the compression in each cylinder and see what you get.

  5. #5
    hi there, this is why i came to this site, cause i knew you guys would know and its much appreciated. The cylinder nearest the back of the ski has no compression at all. Piston is running free and nothing looks damaged or broken ( from what we can see ). Any clues to what ill be looking when when its opened up, would be appreciated

  6. #6
    Nothing like getting air, while sitting in a chair VonnerNIX's Avatar
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    Just take the head off and take some pictures. People here will be able to try and help diagnose what went wrong and what needs to be fixed.

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