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  1. #1
    PWCToday Newbie
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    Feb 2017
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    Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    Hello Everyone!

    So I have an early 90's Kawasaki Sport Cruiser with a stock 650/38mm carb on it. When I bought it, it had been sitting for quite some time, but ran really well. Then it began bogging down and you'd have to feather the throttle to get it up to speed. Now, it will idle all day long really nice, but immediately bogs down when throttle is applied, to the point the motor doesn't even rev above idle. Below is what I have done so far and I'm really out of ideas. I've pulled/replaced the plugs several times and they are always wet, which makes me wonder if it could still be a fuel delivery issue? If it was running lean or starved for gas, would the plugs be dry? Also, I have a primer installed in it as well and I blast in some additional gas, it doesnít rev any higher and if anything, bogs down more. Initially the carb was set with the idle mixture adjustment 2 revolutions open and high mixture set at 1 revolution open. I set them back to 5/8 rev for idle, 1 rev for high, which were the book specs and saw no change. Also, since the issue predates the carb rebuild, I donít believe the adjustments are a factor in the issue.

    Carb removed/rebuild by a shop
    All fuel lines replaced and external inline filter added
    Checked compression, 135psi in both cylinders
    Pump drive removed and rebuild

    Any help or ideas would be greatly appreciated!!

    Thanks!!

  2. #2
    Top Dog bandit88's Avatar
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    May 2014
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    Green Bay WI
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    Re: Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    I would start with checking the reeds and going through the ignition.
    -95 750SXI
    -86 440 with PJS800 conversion - http://www.pwctoday.com/showthread.php?t=466927
    -90 TS650
    -91 300SX

  3. #3
    PWCToday Newbie
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    Re: Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    Quote Originally Posted by bandit88 View Post
    I would start with checking the reeds and going through the ignition.
    Super, thanks for the reply! So you would agree that since the plugs are wet and the primer has no affect, I could probably rule out the fuel system?

    Do you know if there is a way to check why the ignition would drop out when it rev's beyond idle? Or would I have to just start throwing some parts at it? Like I mentioned it idles great and would run all day long like that. Also is there any chance that running a 24:1 fuel/oil mixture could cause something like this? When I swapped over to pre-mix I wasn't sure what exactly was in the tank, so I was pretty liberal with the oil. What I keep going back to though, is that I had the exact same issue before the oil premix/carb rebuild. I will say it smokes like crazy, I was just attributing that to the potential flooding situation.

    THANKS!!!!

  4. #4
    Top Dog bandit88's Avatar
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    Re: Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    Well I would check the reeds first, if they are broken it will cause the motor to run rich. Then for the ignition, best thing to do is to get a manual and start testing components. A weak spark will run fine out of the water or at idle but will give out and the ski will load up as if its running rich. If you find that one of the coils or CDI is going out, replace it with a good used OEM one or send it to Jet Ski Solutions for rebuild. All of the aftermarket OEM replacement electrical parts are junk and will give you more issues that you have now. Also check out the TCJP (Twin City Jet Pilots) page on Facebook. Lots of helpful people on there and im sure you could find someone to help if you need it.
    -95 750SXI
    -86 440 with PJS800 conversion - http://www.pwctoday.com/showthread.php?t=466927
    -90 TS650
    -91 300SX

  5. #5
    PWCToday Newbie
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    Feb 2017
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    Minnesota
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    Re: Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    Awesome, thanks for the advice. I will start there and look up the TCJP's as well!

  6. #6
    PWCToday Newbie
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    Re: Kawasaki 650 SC running great at idle, bogs down with any throttle applied

    Hey Everyone!

    Just wanted to post an update and see if anyone has some more input for me.

    So I checked the reeds and ignition and everything looks perfect. It still idles great, but bogs when fuel is applied. I tried turning off the gas when running it and it instantly has full power and takes off like a bat out of hell until it runs out of gas! So it is definetly an excess fuel issue. The odd thing is it developed this before the carb was rebuilt, so Im hesitant to think its the carb. Would a return fuel line restriction cause this? The needles are set to stock, but leaning them out didnt seem to effect it. Should I just keep trying to lean out the high speed jet? Are there any other things I should be looking for?

    Any help or ideas is greatly appreciated!!
    Thanks!!!

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