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  1. #1

    Question about 1999 GP1200 before deciding to purchase insight/help

    Hey guys,

    So I am looking at buying a used Yamaha GP1200 (this is NOT the GP1200R version). I just have a few questions for you all who have spent the time rebuilding these jet-skiis and have experience with these skiis. Now, the guy told me that the first 2 cylinders have 125psi compression and the last 1 cylinder has no compression. Which almost definitely needs to be rebuilt with a new piston ring set and resleeve. He got that ski from a trade and really don't know much about it. Anyway, how much would it cost (ballpark) to rebuild this engine? He says that the engine will still start and run but it runs rough. I plan on working on it myself. I just would like to have ya'lls input on this. Is it worth buying and fixing up? Or should I just pass on it? Guy's asking $1000 which i think is a deal. I just dont get how it doesnt have 1 cylinder have no compression because usually all the cylinders wear out pretty much at the same rate. Also how reliable are they?

    I haven't seen the ski in person - just saw pictures on the net and talked to the guy on the phone, but from what it looks like, body is definitely clean and no cracks and stuff on the hull. Also comes with a trailer.

    Input from you guys are greatly appreciated. Thanks.

    Bford


  2. #2

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    There can be a number of cause , a lead at the rear crank seal that cause lean condition. Or oil line came off if it is not premixed. And 1 piston going out is pretty common.

  3. #3
    I see so 1 cylinder going out is pretty common because of all those issues you mentioned (rear crank seal, and or oil line came off and if its not premixed) .

    Now, do you think that this is worth fixing? I know I would have to find what caused the problem, so does that mean I will have to disassemble the entire engine? Like crack open the case since there might be tiny bits of metal shaving or something in? Or since this is pretty common, can I getaway with just rebuilding that 1 cylinder without compression and call it done?

  4. #4
    that's a good deal. where is it located?
    I think it's worth fixing, if you want to find out what caused it then you'll probably have to tear apart the engine. is it modified or bone stock? I hear the 65U engine is more reliable than the 66V engines.

  5. #5
    Its in Georgia. I'm almost positive that the engine is bone stock. I assume that the 66V engine is the one in the GP1200R's? Yeah I believe its important to know what caused the issue before fixing it so its definitely gonna have to get torn apart and checked.

    I also forgot to mention that the skii has 160hrs on the clock.

    Here are some of the pictures of the ski:

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  6. #6

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    I just rebuild two 65U. Yes, you have to take everything out, because you need to run some test on it. You need to pressure test the engine to make sure it is not leaking and replete the test after rebuild to make sure everything is seal. On the broken piston, you want to see how "bad" the sleeve is damage. If it is deep, you might need to overbore it. It means using a bigger size piston; in that case, you might want to change all three pistons to the same size. If the piston is the only problem, you can get it done yourself for about $250-$500.

    Remember to do the test, remember fins the problem before taking everything apart.

  7. #7
    thats definitely helpful birdgod. So your recommended procedure would be (correct me if im wrong):

    1.) Pressure test engine before disassembly (do i do the pressure test while its in or out of the hull?
    2.) Check cylinder wall - if I dont need to overbore, I could just buy a new piston kit for it and have the cylinder honed right?
    - I saw on ebay that its about $450 for a complete top end rebuild kit
    3.) Check the engine more to see if there are some stuff that needs repaired/replaced (Do I have to crack open the case when I'm doing this repair or will removing just the head be enough?) Do I need special tools?
    4.) If all is ok, reassemble engine with the new parts in and when assembled, do a pressure test again to see if there are any leaks - if all good then put back to hull

    Is this right? I'll probably have alot of questions about this once I get the ski and start working on it.

  8. #8

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    Pull the plugs, push the piston of the bad cylinder down with something soft, and use a small flashlight to look through the plug hole. You should be able to see the piston top and some of the cylinder and tell if it's something like a minor ring stick, or something worse.

  9. #9
    Yamaha artisan Cutlass's Avatar
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    Quote Originally Posted by bford View Post
    thats definitely helpful birdgod. So your recommended procedure would be (correct me if im wrong):

    1.) Pressure test engine before disassembly (do i do the pressure test while its in or out of the hull?
    2.) Check cylinder wall - if I dont need to overbore, I could just buy a new piston kit for it and have the cylinder honed right?
    - I saw on ebay that its about $450 for a complete top end rebuild kit
    3.) Check the engine more to see if there are some stuff that needs repaired/replaced (Do I have to crack open the case when I'm doing this repair or will removing just the head be enough?) Do I need special tools?
    4.) If all is ok, reassemble engine with the new parts in and when assembled, do a pressure test again to see if there are any leaks - if all good then put back to hull

    Is this right? I'll probably have alot of questions about this once I get the ski and start working on it.
    That's about right. You'll want to clean and rebuild the 3 carbs also. These GPs are a blast when you get it up and running. They are reliable too, but there are things you can do to make them even more reliable. Just search around here. You'll probably end up spending more then you think.

  10. #10
    I would like to just get it in stock fully working condition first though. I just hope that I don't have to spend more money than what its worth. I mean if I can fix this thing well below what they're going for then I'm good. I just don't want to end up buying it then realize that I will have to put alot more money to get it running - cuz if so I might as well buy an already running ski - save me the initial work needed

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