SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
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    Eureka, MO
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    Default 98 Kawasaki 900 STX with new SBT Engine - bogging

    A friend of mine has a completely stock 98 Kawasaki 900 STX with about 50 hours on it. The ski was running very well until he injested some water and hydrolocked the engine bending a rod. The ski sat for about two years and then he got a replacement engine from SBT.

    He followed the SBT break in procedure until the part where you start running over Ĺ throttle. The ski idles well, and from a stop if you pin the throttle it accelerates good for 4 or 5 seconds up to about 30+ mph and then it starts to bog. If you back off on the throttle it will run very well at 30 mph. If you leave the throttle pinned it continues to bog and it has completely stalled a couple of times. If you accelerate to 30 mph and back off the throttle when it bogs, and then nail the throttle again at 30 mph you get the same bog.

    We have checked compression and got 110 psig on each cylinder with my cheap gauge.
    Have changed the spark plugs 3 times, thinking they might be fouling out from the extra break-in oil. We removed the gas tank and cleaned the in-tank filters, although they were very clean to begin with. Changed the inline fuel filter. Using new gas. Disassembled the Keihin CDK2 carbs and cleaned everything, although they looked great to begin with.

    The only thing we didnít do on the carbs is split the housing for the fuel pumps as we didnít have the special Tamper Proof Torx Bit.

    We did not check the timing, do you need to do that on this ski when replacing the engine? We are at a loss as to what to check next, any suggestions, comments would be appreciated.

    Thanks,

    Dan
    drb

  2. #2
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    Timing is non adjustable, nor is it your problem.

    I suggest getting rebuild kits, and the proper torx bit, then rebuilding the carbs.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  3. #3
    Joined
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    From
    Eureka, MO
    Posts
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    Quote Originally Posted by Technical Support
    Timing is non adjustable, nor is it your problem.

    I suggest getting rebuild kits, and the proper torx bit, then rebuilding the carbs.
    Thanks for your quick response. The carbs looked great but I realize that looks can be deceiving. Could it be ignition related? Anything in this area that we can check?

    Thanks,

    Dan
    drb

  4. #4
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    No, that does not sound ignition related.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  5. #5
    Joined
    Aug 2002
    From
    Eureka, MO
    Posts
    86

    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    Thanks again - we will rebuild the carbs. Just out of curriosity what would go wrong with the carbs. They were fine before the hydrolock. When we took them apart they were extremely clean no rust or debris at all. The needles looked great and appeared to easily pop off the seats. Filters werew clean. Would a diaphram go bad just from sitting?

    Thanks again,

    Dan
    drb

  6. #6
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    Yes, sitting is what takes them out. You can't tell if gaskets seal well, or if a diaphram flexes correctly or has pin holes just from looking.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  7. #7
    Joined
    Aug 2002
    From
    Eureka, MO
    Posts
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    thanks tech support we will get some carb rebuild kits from you and try that


    Dan
    drb

  8. #8
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    From
    Eureka, MO
    Posts
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    We bought the carb rebuild kits from SBT and installed them. We didn't check popoff because we didn't have the popoff tester, so we reused the same springs that were in it.

    We seem to be getting closer, the ski starts much easier than it did before, and most of the bogging is gone. It now accelerates good from an idle, and runs ok up to a top speed of 40 mph (on the speedo). This is down from about 53-55 mph before the rebuilt motor was installed. There is a slight "miss" at WOT. It bogged once or twice but the rest of the time it accelerated decent with the WOT "miss" and lower top speed. Tried loosening the gas cap and playing with the fuel selector switch (on/reserve), neither thing helped.

    Any other idea's on what we can try before we give up and take it to a dealer?

    Thanks,

    Dan

    P.S. - do you know what the stock setting is for the low and high speed adjusters on the carbs?
    drb

  9. #9
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    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  10. #10
    Joined
    Aug 2002
    From
    Eureka, MO
    Posts
    86

    Default Re: 98 Kawasaki 900 STX with new SBT Engine - bogging

    thanks for the carb settings - I think we are very close to that now but I will check again.

    Not sure of top RPM's because the ski doesn't have a tach.

    Any other idea's on what would be causing the ski to "miss" and not reach peak speed?

    Thanks,

    Dan
    drb

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