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  1. #1
    RXP in upper Michigan flnsx's Avatar
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    900zxi rpms are fine but runs slow. HELP PLEASE!

    We have a 95 ZXI 900 with about 15 hours in it.

    It would run about 53 mph (on GPS) with me on it 190 pounds at the beginning of the summer.

    I converted it to pre-mix and now it will only run 46mph. I have run it with 89 octane and 93. I have run it at 50 to 1 and 40 to 1. Nothing mattered. It still only runs 46.

    RPMS say 7500. It seems to run fine once it warms up. It is very boggy at first.

    Could this be a compression issue? Nothing is in the pump and the impeller is 100 fine. I replaced the fuel filter with a fram a month ago.

    Can anyone suggest a course of action?
    Last edited by flnsx; 09-23-2007 at 09:52 PM.


  2. #2
    axgrider73's Avatar
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    Did you adjust the carbs to account for the oil when you converted to pre-mix?

    Have you done any WOT plug chops?

  3. #3
    RXP in upper Michigan flnsx's Avatar
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    I didn't touch the carbs at all.

    Also what is a wide open throttle plug chop? Cutting the engine at WOT and then checking the plugs?

    Can you tell me why it would run 7500 rpms but be 7mph down?

    Thanks for the reply!

  4. #4
    btldigger's Avatar
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    It may be running the same speed you cant go by the speedo they lie like a cheap watch. Try using a gps then compare speeds with others that have the same model. If you had a compression issue it would probably be down on rpm.

  5. #5
    RXP in upper Michigan flnsx's Avatar
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    I forgot to put in the original post that those speeds are on my GPS not the skis speedo.

    That is a good sign about the RPM's and compression. I wonder what could be causing the slow speeds if the pump is fine.

    Could there be water in the engine you think? I just replaced the sprak plugs and it seems to be running rich but I don’t think that could kill off 7mph do you?

  6. #6
    btldigger's Avatar
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    Quote Originally Posted by flnsx View Post
    I forgot to put in the original post that those speeds are on my GPS not the skis speedo.

    That is a good sign about the RPM's and compression. I wonder what could be causing the slow speeds if the pump is fine.

    Could there be water in the engine you think? I just replaced the sprak plugs and it seems to be running rich but I don’t think that could kill off 7mph do you?

    Not likely water in engine. I would check impeller to wear ring clearance that could kill the speed. Did you notice a difference when you changed the fuel filter. I have heard automotive filters are too restrictive but I would think that would bring the rpm down.

  7. #7
    axgrider73's Avatar
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    If it was anything engine related the rpm's would have to drop. Unless your tach isn't reading accurately. HMMM.

    Are you using a factory tach?

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