787 Low Speed Needle Adjustments, how do you like to set it what are you looking for? - Page 2
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  1. #11
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 787 Low Speed Needle Adjustments, how do you like to set it what are you looking

    Quote Originally Posted by 95xprider View Post
    No not wingin it.
    Just rebuilt carbs and was having some issues at low rpm, but thinking it might have been a wire connection.
    Still seems like wide out rpm might be a little low at 6600?
    seem to be having multiple problems, thinking I might have air leaking into pump, seems like its not hooking up on takeoff, would that give me low rpm though?
    I was thing the opposite?
    Simple stuff first. Are the spark plugs fouled? Are the rave
    valves leaking? or not moving freely?

    Check your water regulator on the waterbox. If you open
    it up and you can easily pull it out of the housing, or the
    clamp fell off, it needs to be repaired.

    The water regulator is supposed to decrease water to the pipe
    as rpm increases, if it doesn't it it will reduce peak rpm.

    Problems with cavitation out of the hole are often caused by a
    lack of grease in the drive line boot. Is the drive line boot leaking
    or needs grease?

    If there are black carbon streaks leading to the pump, the pump
    may be sucking exhaust into the pump. Another common cause
    is leading edge rock damage.

    Did you replace the springs? Lower Pop-off will cause the carbs
    to run richer.

    Did you replace the o-ring on the seat?

    A rich pilot (low speed) screw will kill peak rpm. Did you test the
    pop-off? Pop-off should be tested with the carb disassembled,
    and assembled. The pressure should be the same. 80gr springs
    and 1.5 seats should yield 38psi.





    Bill M.
    Attached Images Attached Images
    Last edited by wmazz; 07-18-2022 at 11:39 PM.
    Horsepower == Speed, RPM != Speed



  2. #12
    PWCToday Newbie
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    Re: 787 Low Speed Needle Adjustments, how do you like to set it what are you looking

    Quote Originally Posted by wmazz View Post
    Simple stuff first. Are the spark plugs fouled? Are the rave
    valves leaking? or not moving freely?

    Check your water regulator on the waterbox. If you open
    it up and you can easily pull it out of the housing, or the
    clamp fell off, it needs to be repaired.

    The water regulator is supposed to decrease water to the pipe
    as rpm increases, if it doesn't it it will reduce peak rpm.

    Problems with cavitation out of the hole are often caused by a
    lack of grease in the drive line boot. Is the drive line boot leaking
    or needs grease?

    If there are black carbon streaks leading to the pump, the pump
    may be sucking exhaust into the pump. Another common cause
    is leading edge rock damage.

    Did you replace the springs? Lower Pop-off will cause the carbs
    to run richer.

    Did you replace the o-ring on the seat?

    A rich pilot (low speed) screw will kill peak rpm. Did you test the
    pop-off? Pop-off should be tested with the carb disassembled,
    and assembled. The pressure should be the same. 80gr springs
    and 1.5 seats should yield 38psi.





    Bill M.
    Plugs are new,
    Water regulator has been rebuilt, but I will verify it is working properly.
    Rave valves look good and are free.
    Pretty sure I greased the new boot, I put on but will double check.
    Impeller looks good. Not sure about carbon streaks.
    Pop off is set at 38 with the right springs and new needle and seats.
    Thanks
    Can the carbon seal cause the cavitation if the rubber boot isn’t putting enough pressure on the carbon seal?

  3. #13
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
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    Re: 787 Low Speed Needle Adjustments, how do you like to set it what are you looking

    I just got through with one of these with a serious cavitation issue, on mine it was the Pump support not sealed to the hull properly, I know it's a big job to pull everything and reseal it but it did fix the issue on my ski , eleminate all the simple stuff first.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    WWSRD , What would Speed Racer do ?

  4. #14
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 787 Low Speed Needle Adjustments, how do you like to set it what are you looking

    Quote Originally Posted by 95xprider View Post
    Can the carbon seal cause the cavitation if the rubber boot isnít putting enough pressure on the carbon seal?
    Yes, that is a common cause. People use zip ties or hose
    clamps on the driveline boot, and it leaks down or develops
    a hole.

    The driveline boot pushes the driveline against carbon ring

    I would spend time on the boot because it is easy before the
    pump support.

    Quote Originally Posted by WFO Speedracer View Post
    I just got through with one of these with a serious cavitation issue, on mine it was the Pump support not sealed to the hull properly, I know it's a big job to pull everything and reseal it but it did fix the issue on my ski , eleminate all the simple stuff first.
    Quote Originally Posted by 95xprider View Post
    Not sure about carbon streaks.
    Easier to see without the pump removed. I have pulled pump shoes
    for the 96' but it was a warranty problem on the 97' with the plastic
    pump support.

    Quote Originally Posted by 95xprider View Post
    Plugs are new,
    Water regulator has been rebuilt, but I will verify it is working properly.
    Give it a tug and see if it comes out easily.


    Bill M.
    Horsepower == Speed, RPM != Speed



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