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  1. #1

    750 sx won't stay running at idle, doesn't run correct period.

    Hey guys,

    I have a few questions maybe someone here can answer.

    I've been working on a friends 1994 750 sx. It has new rings (compression at 132psi both), new carb kit installed and pop-off adjusted as per specs recieved from sbt tech support, the coils and stator have been rebuilt by jetski solutions. At the water it won't stay idleing unless I adjust the idle stop open enought that you can't hold ski still to board in shallow water. When you give it gas it sounds like one cylinder that wasn't running is now running and it shoots across the water like it was fired from a cannon.

    On the trailer with water hose hoked up, I can get it to idle down but it only runs on the back cylinder. I know this because if I pull the spark plug lead off the front cylinder nothing happens, when I pull the back one the engine dies. Also I get a lot of gas/oil mix coming out of exhaust running down driveway. If i start and idle it on water hose when it is cold the front cylinder never gets warm unless I rev engine, then I can hear it kick in, and feel some heat on that side of the block.

    The guy who owns the ski was asking me if it is designed to idle on one cylinder and the other cylinder only run when you open the throttle.
    We were also wondering why kawasaki went to two carbs on the later model of this ski. We think it would be easier to tune each cyclinder individually with twin carbs.

    I also told him I would like to see the compression up a little higher (at least around 150).
    We have the kawasaki service manual for this model but I find it to be a little short in the troubleshooting dept. We talked about doing the cylinder exchange from sbt or changing to dual carbs, but he doesn't have the money to do both. Maybe we just need to run it longer on the new rings but I don't know.

    I hope somebody can share some ideas about this craft. Thanks in advance pwcdaddy.

    Forgot- it has new bottom end seals and has been leak tested also new carb kit and new needle and seat>
    Last edited by pwcdaddy; 03-18-2012 at 03:29 PM. Reason: additional information

  2. #2
    It is designed to run on both cylinders all the time.

  3. #3
    When on the trailer disconnect the spark plug wires,using a spark plug tester make sure you have spark at both wires...

    Also take off the air filter and make sure you see fuel coming out of each carb,at idle..

  4. #4
    Mulefoot-sorry could have said this already but I have spark on both cylinders at idle (tested both with spark testers) and its a single carb engine. Which is why I am befuddled.

  5. #5
    It really sounds air/fuel related.. ..did you rebuild the carb? whats the low/high screw settings right now? What is the pop off set at?

    I did install twin carbs on buddy's 92sx a few years back..It made a huge difference!

  6. #6
    FYI-Having twin carbs can also be a hassle,more to adjust

  7. #7
    Whenever you have new pistons/rings etc..there is a break in perriod/and a proper method,You should be running a really rich mixture for the first full tank,and obviously no wot runs across the lake..but first u need to get it to run right,now you gotta double chek all your work,all fuel/pulse lines are going to the right ports etc..Timing is at stock specs? tried different spark plugs..maybe 1 is just no good.

  8. #8
    I don't recall exact pop off but two months ago when I was doing the carb I called sbt for the spec I think its 23 psi but dont remember, but I had to change out needle and seat and spring to get it right. It has been waiting for a nice weekend to get it to the lake. The low speed needle I had set at 1 turn open (book calls for 7/8 +/- 1/ when we got it to lake. I tried to adjust it richer but made no difference. I haven't checked timing other then verrifing stator is installed correctly.

  9. #9
    steve45's Avatar
    Join Date
    Feb 2008
    What are the spark plugs telling you?

    You might have a bad spark plug wire (pretty common). Unscrew the rubber boot from the wire, then see if you can pull any wire strands out with some needle nose pliers. Cut the wire back a 1/2" or so to get to good wire and re-install the spark plug boot

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