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  1. #1

    gp1200 stops dead , restarts and dies again

    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. i did jump another ski from my ski, eaxct same battery , 1 hour before my problem occured, much appreciated, chris


  2. #2
    It sounds like a partial seizure to me. The piston is getting too hot for some reason and expanding until it can no longer move in the cylinder. This is why it will not restart until the piston cools and releases itself. I would start with doing a compression test. You will prob find a bad cylinder. Then I would see if the guy who did the work prior will guarantee his work. Good luck!

  3. #3
    Hydrotherapy's Avatar
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    get it apart and we can go through some pics

  4. #4
    Xl760 on the water/ gp760 in shop for paint
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    Is the oil injection still hooked up or is it converted to premix??

  5. #5
    Quote Originally Posted by ON EMPTY View Post
    Is the oil injection still hooked up or is it converted to premix??

    Its still on injection. The oil low light had come on a few times but once i stopped and restarted it went out and had plenty of yamalube in it. I managed to check compression and nothing in the rear cylinder nothing at all. other 2 are good. piston is moving up and down freely, dosent look damaged or scored through the peephole . gonna hopefully get the head off tomorrow, im no mechanic but i do have help. Theres no warranty as such, i live in Uk and it was fixed in poland. I had plenty use in the sea and first time in fresh water it blows, just my luck. I have 4 skis all with problems but this is the main one i use. will try get pics etc and rear the tutorials on here. its an awesome specialised website

  6. #6
    Stripped head tonight, and im gonna try and upload pics if i can work out how to do it. The piston is fried. the picture of the head where it is pitted is not from the same cylinder, it looks like that piston was replaced which coincides with the info i received when i bought the ski. compression is fine on this cylinder. What info im looking for is how to do this, what do you guys suggest. Cylinder wall i reckon needs rebored as it is marked. I dont mind spending the money to fix it, i just wouldnt want same thing to happen again, is their something that might have caused it. I was going flat out i think when it happened , i hadnt been that fast on it before, first time id been on calm water . any help much appreciated. anybody got problems with laptops and ill happily help in return. thanks

  7. #7

  8. #8

    hopefully these are smaller photos

    Click image for larger version. 

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  9. #9
    Hydrotherapy's Avatar
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    that pots lean......you gotta tare down and inspect crank now as chances are the damage you can see on head is big end pieces come up through the transfer port and smash about between piston and head before being spat out...you may be lucky with crank but its unlikely tho

    sorry for bad news

    pm me your mob if you want a chat

  10. #10
    Flying Scotsman's Avatar
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    Main cause of seizure is carbs.GP1200 are notorious for needing carbs maintained.When they go bad it ususlly ends up costing you a motor.Strip it all down and look at the crank,then you need to get the cylinders bored and honed for oversize piostons.(all 3 cylinders )

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