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  1. #1
    demne's Avatar
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    96 GTX with no power/ RPMs on water

    I have a 96 GTX with 787 motor, brand new only an hour (maybe) of break in time.
    When I start it on the trailer it revs up fine. On the water it won't go over about 3200+ rpm, I have briefly had it up to 4200+ hitting maybe 25MPH

    So whats been done:
    - All fuel lines have been replaced
    - Carbs are clean, nothing in the screens - actually there is no screen
    - RAVE valves clean
    - Waterbox valve fine
    - New plugs, wires, coil

    I pulled the carbs & checked the Hi/Low, no improvement.
    Double checked them and they seemed to be adjusted backwards, so I switched them setting wise. However this made no difference, I would have though completely reversing the hi/low would have made some sort of change/difference. On the water I tried changing the the top screw's 1/4 turn each way with no change.

    So what should I try next?
    Where can I find the model number of the carb?
    Is the Hi on the top or bottom of the carb when installed - just to be sure.
    Could premix & the oil injection (cause Im breaking it in) have that large of an effect on running



    Thanks, Jason


  2. #2

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    Why does it have a new motor? It sounds like you have a fuel metering issue with the carbs. There are many small pathways than can be the problem. Did you rebuild the carbs with complete pressure testing, check for leaks around the N/S??? Did you clean the fuel selector valve. We have all been down this road. The fact that you don't know what carbs you have concerns me on your carb work. BTW, they are Mikuni SN40-I if OEM. Did you pull the jets and compare to stock? Give us some more info on the carbs.

  3. #3
    demne's Avatar
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    Previous owner put a new motor in it then couldn't get it to spark, I bought it & got spark ...
    The carbs were apparently rebuilt, and should be stock. I went to get a carb kit & when told them I wanted BN40I(SB) according to seadoosource.com/carbreference.html, they told me that's not the stock carb. So I was looking for a serial number to cross reference.

    Im going to pull the carbs & pull them apart.

    for what its worth;

    Click image for larger version. 

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  4. #4

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    HS is on top, look for the H cast in the body. If the engine is stock, the HS is closed, the LS are 1-1.25. Follow the instructions on seadoosource for testing the pump, pump valves, and the N/S assy and let us know for sure what jetting you have. Pull the N/S, and the jets. Spray cleaner through jet areas and look for the 3 holes in the bore on the pilot and the big hole in the bomb site for main. Pull the two screws and spray there also. The fuel selector has an o-ring in it that can go bad allowing air into the system as well. There are many possible issues, but they can be found.

  5. #5
    Myself's Avatar
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    Have you checked your voltage at the battery while running and while revving it?

  6. #6
    demne's Avatar
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    Power is good, brand new battery, new stator, plugs, wires, caps, coil.

  7. #7
    wkuadam07's Avatar
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    While the carbs are off pull the rotary valve cover and check the rotary valve timing, i had a ski brought to me once with very similar symptoms and it was WAY out of time. I sounded great and revved well dry, but in the water it was a turd... While you are in there i would also check the rotary valve clearance, this also can cause a lot of loss of performance.

  8. #8
    Myself's Avatar
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    Quote Originally Posted by demne View Post
    Power is good, brand new battery, new stator, plugs, wires, caps, coil.
    OK, what was the voltage while cranking....
    And while revving it.......

  9. #9
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    I'm casting the evil on on the fact that the internal carb filters are missing..what else did they decide to leave out? or not check?

    I'd go right to the pop off test and in my mind, the float arm is way out of adjustment, or the wrong springs wee installed.

    nothing worse then trying to diagnose a carb issue...when the rebuilder wasn't going by the book. ( who leaves out the internal filters?)

  10. #10

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    Quote Originally Posted by nmpeter View Post
    I'm casting the evil on on the fact that the internal carb filters are missing..what else did they decide to leave out? or not check?

    I'd go right to the pop off test and in my mind, the float arm is way out of adjustment, or the wrong springs wee installed.

    nothing worse then trying to diagnose a carb issue...when the rebuilder wasn't going by the book. ( who leaves out the internal filters?)
    Hey Captain,
    I love your insight and experience, but I have actually consider leaving the internal filters out, LOL. IMO, the filters catch little stuff that would have passed through the jets without issue only to eventually clog the filter to create a lean condition leading to damage. I always clean them and replace them, but I have wondered many times if that was the right thing to do. So I haven't done it, but I sure have thought about it.

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