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  1. #1
    PWCToday Newbie Clitbox2003's Avatar
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    Angry Kawasaki 650sx won't rev high

    I have recently completed a complete rebuild of an approx 1989 650SX stand up. Rebuilt motor (148 & 150 comp) all new lines, pipes, plugs, lead, cables and carby kit.
    Engine starts fine with minimal use of primer. Idles well. Fuel flow is good. However every time I accelerate it dies and almost stalls. I have been able to get it to rev to approx 80% with choke partially on but then it floods. Have tried adjusting high mixture screw from 1/8 to 2 1/2 turns with no change.
    Does anyone have any suggestions. It has a Keihin CDK II Carburetor.
    Regards
    Clinton

  2. #2
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    Re: Kawasaki 650sx won't rev high

    How's your check valve on the tank
    1989 650sx - 750 SP swap, Mariner large chamber pipe / intake grate / rideplate / 4 deg JetWorks bars, finger throttle, custom paint, dual SBN38

    1992 750SX - AC alum pole, factory wet pipe, BCW intake, Ocean Pro rp, westcoast scoop, (soon) westcoast intake w. dual SBN44

  3. #3
    Top Dog hooka-2's Avatar
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    Re: Kawasaki 650sx won't rev high

    Quote Originally Posted by StuRat View Post
    How's your check valve on the tank
    The keihins carbs don't require pressurization like the old sb mikunis did. It sounds like maybe your pop off is too high if it wants to stall off idle that or your low speed jet is too small or partially/completely clogged. Did you change the spring for the needle and seat during rebuild? or if you changed the little arm that opens the needle did you check the adjustment height?
    90 X2 (750), 92 X2 (750), 93 X2 (750),93 X2 (750), 99 Ultra 150(sold) 1995 Waveblaster 1

  4. #4
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    Re: Kawasaki 650sx won't rev high

    Quote Originally Posted by hooka-2 View Post
    The keihins carbs don't require pressurization like the old sb mikunis did. It sounds like maybe your pop off is too high if it wants to stall off idle that or your low speed jet is too small or partially/completely clogged. Did you change the spring for the needle and seat during rebuild? or if you changed the little arm that opens the needle did you check the adjustment height?

    Yeah that's just wrong. CDK2 need pressure and a bad/failing check valve will do exactly what he is describing.
    1989 650sx - 750 SP swap, Mariner large chamber pipe / intake grate / rideplate / 4 deg JetWorks bars, finger throttle, custom paint, dual SBN38

    1992 750SX - AC alum pole, factory wet pipe, BCW intake, Ocean Pro rp, westcoast scoop, (soon) westcoast intake w. dual SBN44

  5. #5
    Top Dog hooka-2's Avatar
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    Re: Kawasaki 650sx won't rev high

    Quote Originally Posted by StuRat View Post
    Yeah that's just wrong. CDK2 need pressure and a bad/failing check valve will do exactly what he is describing.
    How come they will run fine with the gas cap off then? just saying. The check valve is only there to prevent a fuel spill. PERIOD
    90 X2 (750), 92 X2 (750), 93 X2 (750),93 X2 (750), 99 Ultra 150(sold) 1995 Waveblaster 1

  6. #6
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    Re: Kawasaki 650sx won't rev high

    I run the same, wearing boxers, briefs, or my thong (even backwards).

    I like long walks on the beach, dirty smuts, and hate swimming my ski back to shore.

    .......and fuk the smurf's.
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  7. #7
    Top Dog bandit88's Avatar
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    Re: Kawasaki 650sx won't rev high

    Quote Originally Posted by hooka-2 View Post
    How come they will run fine with the gas cap off then? just saying. The check valve is only there to prevent a fuel spill. PERIOD
    agreed.

    Did you use OEM parts or genuine Kehin when you rebuilt the carb? Aftermarket carb kits are no good.
    -95 750SXI
    -86 440 with PJS800 conversion
    -90 TS650

  8. #8
    I dream skis JC-SuperJet's Avatar
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    Re: Kawasaki 650sx won't rev high

    After you rebuilt the Carbs, did you perform a pop-off test? Did you replace the Needle Valve Body O-ring?

    Sometimes fuel leaks past the NV Body O-ring before proper pop-off pressure is reached and thus distorting the carburetion.

    Symptoms are engine will not hold steady idle as seen on tachometer, will almost die when throttle is pulled fast, but will transition to high speed if throttle is pulled slowly.

    Do the carb pop-off test and if the fuel bubbles before the Needle Valve pops, then the o-ring is leaking.

    The fuel tank check valve primary purpose is to act as a vacuum breaker (allow air into the tank) to prevent tank collapse as the fuel level drops inside the tank.
    Last edited by JC-SuperJet; 11-14-2017 at 07:04 PM.

  9. #9
    I dream skis JC-SuperJet's Avatar
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    Re: Kawasaki 650sx won't rev high


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