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  1. #1

    Join Date
    Apr 2012
    Location
    Spring hill, Florida
    Posts
    8

    98 gp 1200 problems

    I bought 98 gp1200 not getting any spark with lil over 100 hours on it. I did compression test all cylinders have 105 psi. I have a bunch of extra gp1200 so I thought it would be easy fix. Jetski seems stock beside for spark arrestor and sponsons. First I replaced cdi no difference. Then replaced stator and got spark on all cylinder and got the motor to start. So took it to the water and tested it and jetski wouldn't rev over 5500 and only did about 40 on speedo. Didn't have near power it should. So I pulled plugs and did another compression test and got #1 120 #2 105 #4 115 and middle cylinder had not been firing. So checked it for spark again and has spark outside the cylinder but doesn't seem to be outside the cylinder? I checked carbs seem to be getting fuel and center cylinder seem to be getting to much fuel. It's vibrates on top of lower butterfly valve. But I pulled carbs pulled apart and looks clean and fuel pump seems good. Also checked reeds and there not cracked and seem to seal well. I'm outta ideas on what the problem could be center cylinder still doesn't seem to be firing. Any help would be greatly appreciated.


  2. #2

    Join Date
    Jan 2014
    Location
    Chester, Va
    Posts
    74
    Compression is low in that middle cylinder. It may not be a spark issue at all at this point. Or you may be getting a week spark on top of the low compression. The compression would be my first fix if it were me, then go from there. How do the check valves in the carbs look? Are they creased? Maybe you're needle/seat is leaking in that carb. I'd go ahead and rebuild since you have no idea if they've ever been done. Just my 2 cents. There's a carb setup that's highly recommended by several members here that know their stuff that I use myself. I'd be more than happy to help you if you choose to do it.

  3. #3

    Join Date
    Apr 2012
    Location
    Spring hill, Florida
    Posts
    8
    I always was told that if a motor had over 90psi it would run not sure how true that is. Also the other two cylinders were the same as middle before they actually starting running so I was think if I could get middle cylinder to fire compression might come up closer to other two. As far as carbs I haven't checked the check valves but I will. I thought carbs might need a rebuild but there not giving me the normal symptoms that I have experienced in the past with my other gp1200 motors. Like hard starts and a lean running condition this ski starts quick and easy and all cylinder seem to be getting adequate fuel based on color of other two plugs. But I would be very interested in hearing about the carb setup you guys use as I have this ski and also have a ls2000 with the 1200 non pv motors

  4. #4

    Join Date
    Jan 2014
    Location
    Chester, Va
    Posts
    74
    The general consensus here is the 10% rule for compression. All cylinders need to be within 10% of each other. I'm sure it will run, but the question is will it run right? I don't know why you would be getting spark outside of the cylinder but not inside. You either have spark going to the plug or you don't. If there's fuel dripping from the carbs at idle, and it's sitting on top of the butterfly, then sounds like needle/seats are bad. Someone else may have other ideas. You checked your wires? Switched them to see if it will spark on middle cylinder with the wires switched?

  5. #5

    Join Date
    Apr 2012
    Location
    Spring hill, Florida
    Posts
    8
    Yea I have heard the 10% rule and I agree that it may cause it to run poorly. I'm hoping that if I can find out what's causing the middle cylinder not to run and fix it after running compression may come up like the other two did when I got them running. Yea I've changed coil pack I think I'm just gonna go ahead and focus on carbs and see if those my be the cause of my problem.

  6. #6

    Join Date
    Apr 2012
    Location
    Spring hill, Florida
    Posts
    8
    Had the carbs rebuilt and that's solved the issue guess it was flooding out middle cylinder

  7. #7

    Join Date
    Jan 2014
    Location
    Chester, Va
    Posts
    74
    Glad to hear it.

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