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  1. #1

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    2000 jetski 900 stx not firing on 1 cylinder

    Hello to anyone willing to lend a hand!

    I have a friends 2000 Kawasaki jetski 900stx that was brought to me in need of repair. The jetski was purchased from the original owner in the mid 2000s, not used much by the original owner, and then not used much by the current owner either. In 2010, the owners son took it for a ride across a sand bar and destroyed the jet pump. It was parked in the yard, wrapped up in tarps, and has sat there until june of this year when the owner reached out to me after none of the local dealers would touch it.

    An entire new remanufactured pump later, along with the driveshaft seal carrier, and having to re-glue and glass in the driveshaft hull insert that had seperated from the hull, and freeing the completely frozen crankshaft and allowing oil to soak the bearings, it was ready for some testing to begin.

    Compression was checked, an even 103-105 across all 3 cylinders. New spark plugs were installed, carbs were rebuilt using original springs, new needles and seats included, reeds checked and cleaned, gaskets replaced, fuel tank drained and cleaned.

    Test run time, the ski wont go above 30 mph, wont rev past 5700-5900 rpms. Takes off like a dog but does go on plane, just wont take off any faster than 30. Temp sensor cleaned out, and tested plugged in and un-plugged, no change. Water escaping tell tale as it should. Spark plugs showed beautiful burn on rear 2 cylinders, #1 was clean and wet with gas. Idled the ski in the water and began pulling plug boots off. #1 showed no change, pulling #s 2 and 3 nearly stalled the ski. Trimmed wire on #1 and re-installed boot, still the same issue. Further investigation revealed a broken nut/seal on the wire going to electrical box for that wire, and further investigation revealed the wire had pulled out from the coil on that cylinder. Cleaned up, trimmed wire, and re-installed wire into coil and glued in place, let dry overnight, test again next morning and still same issue. New (aftermarket) coil ordered and installed today, still same issue. Removed spark plug from that cylinder and held against the cylinder head by threaded hole for plug, observed an apparent weak spark.

    Before i left i did not think to pull the other plugs and observe the spark on those cylinders, and i did not try switching the boots around to see if the problem followed the boot. We did replace the spark plug on that cylinder with a different one and the issue persisted.

    At this point i am thinking that the ECM could be bad, or i might have a fuel issue. I did not check pop off pressure in the carbs as i do not have a tool for that, therefore i re-used the original springs. If anyone has testing info for the ecm or stator, that would be helpful.

    From talking to the owner, it sounds like this ski never ran any faster than it does now, leading me to believe this may have been a problem before the sand bar incident. It was evident that someone tried to remove the driveshaft before i took the ski, and that may be where the seal on the electrical box had been broken and wire pulled out, but who knows. The owner knows i'm really chasing my tail at this point, and also understands that due to having sat with a completely siezed engine for an unknown amount of time that this thing may blow up the first time he rides it, but i'm invested at this point and want to see it take off the way that it should atleast once. The shops around me arent interested in taking this in, so i'm hoping someone out there can lead me in the right direction.

  2. #2
    steve45's Avatar
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    Welcome aboard, DMolaver!

    Quote Originally Posted by DMolaver View Post
    and freeing the completely frozen crankshaft and allowing oil to soak the bearings,
    I hate to be the bearer of bad news, but that's your problem. These crankshafts have ball and needle bearings. A 'frozen' crankshaft is junk. It can't be fixed with oil, it can only be replaced or sent to a crankshaft shop for rebuilding. It might run for a little while, but it will self-destruct sooner rather than later. When that happens, expect a rod to break and cut the engine in half.

  3. #3

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    I do understand that its likely to let go. I have rebuilt several 2 stroke engines and understand that this is a time bomb, as does the owner.

    Hoping someone here can point me towards more troubleshooting steps to resolve the lack of spark/ignition on this particular cylinder. As stated above it has good compression which matches other cylinders, and is providing fuel to the cylinder.


  4. #4
    steve45's Avatar
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    I guess I don't understand why you would spend time and money to put together an engine that is destined to self-destruct.

    Oh, well, your call...

  5. #5

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    Because a friend asked me to do what i could with it.

    Not my money, not my problem. I've personally seen frozen engines like this run trouble free for years. Its more likely the rings were stuck to the bores than the crank/crank bearings themselves rusted, to clarify the frozen crank statement.

  6. #6

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    Aug 2021
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    More troubleshooting lead me back to a lack of fuel problem. Removed the diaphragm/needle valve cover from the affected cylinder to find the new (aftermarket) diaphragm to have a bent metal plate, not allowing that needle to fully open. I will report back if this solves the issue. Does anybody have info on the needle arm clearance to the carb body for these CV carbs?

  7. #7
    Myself's Avatar
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    Between 1 and 2mm.

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