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  1. #1

    Kawasaki STX-12f --- No Compression :(

    Hey guys I need some insight on what to do to my motor or should I just take it out to the dealer?

    The ski's RPMs fluctuate and has what I assume is steam coming out of the exhaust (white smoke). I took a compression test and the cylinder closest to the front of the ski has zero compression with random spikes of 50 psi every 3rd or 4th crank, the next one is at ~150ish if I remember correctly, the 3rd cylinder from the front is at about 100 psi and the 4th cylinder is reading similarly to the 2nd cylinder. I bought the ski this way so I don't know it's history.

    I don't think its the head gasket.
    I've changed out valves before but haven't been any deeper into a motor.
    Are changing rings or gasket tough work?
    Is there anyway to know if its the valves, piston rings, or head gasket?

    Thanks for any information y'all can provide me!


  2. #2
    Quote Originally Posted by sumo500 View Post
    Is there anyway to know if its the valves, piston rings, or head gasket?
    None of the above.
    My bet is you have detonated pistons, at least two.
    Use a bore scope and you may be able to see the damage.

  3. #3

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    Does this happen due to engine getting really hot or lean condition?
    If so, I have heard of that in supercharged kawi like the 250, not in a NA like the 15f. What do you think has caused it?
    Quote Originally Posted by meangreenman View Post
    None of the above.
    My bet is you have detonated pistons, at least two.
    Use a bore scope and you may be able to see the damage.

  4. #4
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    If your fuel pump ate it and you continued to run the motor it would be really lean and melt the pistons.

    Sean

  5. #5

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    Shouldn't there be a sensor setting an alarm off over certain temperature or fuel/air mixture?
    I would say it should even shut off the engine in case the rider ignores it!

  6. #6
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    there should be but there is not, the kawi ecu is pretty basic in that regard. In addition to that marine environments are very tough on afr sensors, they wouldn't last more than a few months.

    Sean

  7. #7

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    Thanks Sean!
    There is no harsher environment than marine! I am actually amazed that we hammer these things in salt water to death and they last us as long as they do! They are getting better and better too!

  8. #8
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    No problem, I am here to help out. I will be running an AFR gauge on my 15f when I finish it but more than likely I will tune it and remove it, there is nothing about these gauges or sensors that are cheap.

    Sean

  9. #9
    Crap With damaged pistons, the block should be damaged too right?

  10. #10
    Take the time to smile sirbreaksalot's Avatar
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    Quote Originally Posted by sumo500 View Post
    Crap With damaged pistons, the block should be damaged too right?
    Hang on let's not all get excited and start assuming it's a piston !!
    How's the possibility that the previous owner has had piss poor maintenance and never emptied the waterbox after riding and had caused either a sticky valve or a rusty valve seat.

    Cause a burnt / broke piston typically gives ZERO comp and oil and shut on the plug which the OP mentions nothing of.

    Can we get any more history on the ski !!!
    But to check if. Valve is sticking just do a clearance check on the valves and that will give u a better idea.

    Either way sounds like your head atleast is coming off.

    Waz

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