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900 STX #3 Hole Blown Again

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  • 900 STX #3 Hole Blown Again

    This 1997 stx has used up 3 engines all with #3 piston melted on exhaust side.
    the latest is it will not accelerate at wot and sounds as if it is missing. Pumping throttle gets it going and will run wot all day until you let off. Engine has no mods have gone over carbs countless times. Why is it always # 3 I have read several posts and some answers but the only one that made sense was from Group K about torsioing of the crank. I could not find a fix can the 3rd carb be re-jetted larger or does some one know what the fix is. Thanks any info would be great

  • #2
    Re: 900 STX #3 Hole Blown Again

    Are you using the same crankshaft? If so, you need to verify the indexing.


    Maybe there is a bent/twisted con-rod?

    Has the crankcase been apart?

    Has the complete engine been pressure/leak tested?

    Is it possible that the crankshaft seal is damaged and/or leaking?
    John Kubiak
    Powersports Technical Training Professional
    Las Vegas, Nevada
    Sea-Doo Tech 13736
    PWC Tech since 1988 (22 years)
    PowerSports since 1976 (34 years)
    NEVER BUY TIRES AT A "BLOW-OUT" SALE
    Please do not use Private Messaging, use the forums.

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    • #3
      Re: 900 STX #3 Hole Blown Again

      Originally posted by John Kubiak
      Are you using the same crankshaft? If so, you need to verify the indexing.


      Maybe there is a bent/twisted con-rod?

      Has the crankcase been apart?

      Has the complete engine been pressure/leak tested?

      Is it possible that the crankshaft seal is damaged and/or leaking?
      The 2nd engine was a SBT rebuilt and ran fine for a while when #3 burned I performed pressure and vacuum check all ok. There just seems to me that there is a lot of complaints about #3 cyl burn out. will keep looking for the prob and if I find it I will let you know. Thanks for your input

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      • #4
        Re: 900 STX #3 Hole Blown Again

        If it is not a bent crankshaft or an air leak, then you need to throw more fuel into that clyinder. Yes try rejetting to a larger main jet in that carb.
        Bill O'Neal <br>
        WCM
        <a href="http://www.watercraftmagic.com"

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        • #5
          Re: 900 STX #3 Hole Blown Again

          Did the SBT engine come with carbs?

          What did you do to the carbs before mounting them on your new SBT engine? I hope you fully cleaned them, prior to mounting them on the new short block
          <b>________________________________________
          Not as good as I once was
          But I'm good once, as I ever was!

          Retired 7x, Region 5 stand-up Champion</b>

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          • #6
            Re: 900 STX #3 Hole Blown Again

            new gaskets, reed plates sucking air,fuel not getting to the cyl., fuel line colapsed inside, proper plugs, their is a reason, carbs in sync
            94 gtx, 96XP, 97XP,04 GTC SC,05 RXT & RXP

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            • #7
              Re: 900 STX #3 Hole Blown Again

              This is excellent advise.
              Harry Klemm

              Originally posted by Bill O'Neal2
              If it is not a bent crankshaft or an air leak, then you need to throw more fuel into that clyinder. Yes try rejetting to a larger main jet in that carb.

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