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2004 900 STX high rpm at idle

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  • 2004 900 STX high rpm at idle

    Hello,
    The ski sat for 5 years and we just recently tried getting it running again. Tried cranking with the old gas and of course got nothing. Drained most of it out, filled up with fresh gas, the engine fired and ran...then held a very high idle with the throttle in the idle position. Shut it down, verified the throttle was operating correctly, started up again very quickly. Again, high idle...I'd have to say above 3k rpm. But it sounded normal, like a jet ski. I should mention this is all out of the water. The oil bottle is about half full, likely the same oil from 5 years ago.
    I know cars, not jet skis, but the principles are similar...obviously this is a two stroke engine. From reading around, I think my next steps are to check the spark plugs and compression, the throttle plates to see if one or more are seized open, and the miscellaneous rubber hoses for wear/leaks. It's been sitting so I expect some dry rot.
    What should I add to my list of things to check? What online resources are available to me for specs and parts? Obviously Google helps, that's how I found this site, but I mean specific reliable info on this model.
    I know nothing about this model or any others except what I've learned in the past few days. Ask me about a Jeep and I could talk for days...what years came with this engine or transmission, etc. This is my first adventure with a jet ski. Let me know if I'm leaving anything out.
    Thanks a ton! I'd love to be able to ride this summer!

    -Tim

  • #2
    Re: 2004 900 STX high rpm at idle

    Tim,

    If I were you I would have someone rebuild your carbs, 5 years with old gas sitting in them there is a good chance something has gotten gunked up or is going to once the fresh gas starts flowing. Paying for carb rebuilds now beats replacing a motor from leaning out later. If you are mechanically inclined and want to buy the tools you could tackle this, but I would recommend a professional. New plugs are cheap insurance. The 3k idle speed is to spec for out of the water. Once in the water it should be around 1400. I have been in the same position and was given a 900 stx that had sat for several years and simply changed plugs and ran it, but it was free and not my Primary riding ski....so I could have parted it if things went south.

    Good Luck,

    Chris

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    • #3
      Re: 2004 900 STX high rpm at idle

      Thanks for the reply!
      I have rebuilt many carbs in the past. Never one made for a jet ski. I have tools but how you word it makes it seems like there are special tools needed to rebuild the carbs.
      Is there anything specific I need to pay attention to when rebuilding these carbs that a professional might better recognize than someone who hasn't rebuilt a jet ski specific carburetor?
      Also, the engine seemed to be unusually high at idle. It had to be over the 3k mark, but that's just my own judgement. Definitely didn't seem like it would have been a standard rpm setting for out of the water running.
      Thanks again!
      -Tim

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      • #4
        Re: 2004 900 STX high rpm at idle

        Tim,

        The keihin carbs you have are fairly easy to rebuild. You will need a pop off tester for the needle and seat as well as a kit for each carb. Some people will replace needle and seat and use old spring and go but I advise against this. There should be some good posts of the process if you search the forums or youtube. It will be fairly time consuming for a first timer but an opportunity to learn. If it's idling high there is a chance it is lean... I have seen one run away like a diesel, from heating the piston it is a scary moment of panic...

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        • #5
          Re: 2004 900 STX high rpm at idle

          Awesome, I will search for the rebuild procedures. Are these carbs used on multiple different models? I've been having a hard time finding much on this specific model ski. I'd imagine one tutorial can be applied to most of these types of carbs but I'd rather know what I'm getting into. It's actually my neighbors ski but I get free use of it when I fix it.
          Thanks

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          • #6
            Re: 2004 900 STX high rpm at idle

            Yes, these carbs were used on a few different models. Search for Keihin CDKCV Carb Rebuild. The Keihins are fairly similar. You will not be rebuilding the fuel pump so don't take it apart. It is on the back end carb and feeds all 3 on that model Ski.... if I am remembering correct. Good Luck and If you have questions just post pics and/or ask there are a lot of knowledgeable folks on here.

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            • #7
              Re: 2004 900 STX high rpm at idle

              3k out of the water is way high, and is not spec. It's more like 12-1500 which will be about 1000-1100 in the water. I (along with many others) always reuse the old springs, but check the pop off. Should be around 25psi. Spray some wd40 to submerge the needle to get a accurate number, and cover the needle assy. with a rag so you don't get sprayed when it pops. If it pops at 30psi or higher, put the old needles back in and recheck it. I have been finding that the off brand kit needles are causing a high pop off in the 32-35 range which is way high for Kawasaki's and causes a lean condition and hard starting.
              Be prepared, the CV carbs are very temperamental and can be a real bugger to tune. Be sure and document how many turns from seat the low speed screws are for each carb. They need to be returned to that exact setting.
              The CV carb is used on the 98 and up STX triples, and I think the 98 and up ZXI's, but don't quote me on that. The CV carb was not one of their best ideas and many people replace them with the CDKII carbs.

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