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  1. #1

    '97 GSX - Knock and Vibe

    Working on a '97 GSX right now. It starts right up and feels/sounds like it's running on 1 cylinder, however, it is running on both. 150 psi compression. It has the 1 cylinder running blues on the trailer. Revs out good, otherwise. Has a lot of oil coming from the exhaust. Put it on the water and it has a knocking noise...hard to diagnose where it's coming from...doesn't sound like the bottom end. Once on plane, it runs like a mint top. Bring it down to idle and it does the same old thing. Can't figure it out. Any suggestions are much appreciated.


  2. #2
    The knocking noise is just the the impeller. When you remove the jet pump from the ski to change the pump fluid, remove the cone and you will see a shaft with two flat sides. It will move back and forth which is where the knocking sound at idle is coming from. There is an update kit for it. A new longer cone with a spring and o-ring if I remember correctly. That will apply pressure to the impeller shaft and stop the back and forth knock. It is very common with a lot of different makes and models. For the oil concern, it could either be the injector cable is too tight and advancing the injection too far, or the seals in the rotary vavle housing are leaking. But if the plugs are still keeping choclate brown then don't worry about it, a little extra oil won't hurt it.

  3. #3
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    Quote Originally Posted by Schwarzenegger View Post
    The knocking noise is just the the impeller. When you remove the jet pump from the ski to change the pump fluid, remove the cone and you will see a shaft with two flat sides. It will move back and forth which is where the knocking sound at idle is coming from. There is an update kit for it. A new longer cone with a spring and o-ring if I remember correctly. That will apply pressure to the impeller shaft and stop the back and forth knock. It is very common with a lot of different makes and models. For the oil concern, it could either be the injector cable is too tight and advancing the injection too far, or the seals in the rotary vavle housing are leaking. But if the plugs are still keeping choclate brown then don't worry about it, a little extra oil won't hurt it.
    Did you ever think his Idle speed is to low. Set it to 1500 in the water maybe 3000 on the trailer depending on the Ski .

  4. #4
    That could be as well but even at spec idle speeds it will still rattle down there. The only real cure for it is the updated cone assembly.

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