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  1. #1

    Question Yamaha GP800R problem accelerating

    I am having a problem with my Yamaha GP800R when I accelerate. When I hold the throttle down all the way it will have very high RPMs, but will accelerate very slowly until around 20-30 mph. Once I reach this speed, it will go back to normal and pick up speed at the correct rate. It has no problem reaching its max speed (mid 60s).

    I have checked the impeller and it is not clogged or damaged.
    Any ideas on what the issue could be? This problem only occurs when I am accelerating at full throttle and am going at lower speeds.

    Thanks for your help!


  2. #2
    2005 RXT Red08Ultra250's Avatar
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    shure sounds like cavitation. Something most likely wrong in the pump if impeller is ok. Do these have a wear ring? What is the clearance between pump and impeller?

  3. #3
    whats the update ? on this problem

  4. #4
    Mighty Mouse's Avatar
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    I say too much clearance between wear ring and impeller. Check the clearance. Probabaly time to change one or both.

  5. #5
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    if the clearance is good and the impeller is good, Then it sounds like the felt blew out on the pump shoe you will need to reseal the pump shoe.

  6. #6
    Having similar problem, If I stab on the throttle , will go high rpms for a couple of seconds then shoots OFF like if trash was in the impeller but I check real good and nothing, Clean

    so maybe the wear ring is damage how can i check the Clarence how much suppose to have
    what else can it be the last 2 rides its like this

    thanks in advance

  7. #7

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    Same issue. Any updates.?

  8. #8

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    Quote Originally Posted by jaguarr2012 View Post
    Having similar problem, If I stab on the throttle , will go high rpms for a couple of seconds then shoots OFF like if trash was in the impeller but I check real good and nothing, Clean

    so maybe the wear ring is damage how can i check the Clarence how much suppose to have
    what else can it be the last 2 rides its like this

    thanks in advance

    Start with the simple stuff first as advised in the previous post (Jim's performance). Remove your shoe and reseal it per instructions in the "how to and frequently asked questions" in this forum. Save yourself some money by doing this first.

    If it still cavitates after you reseal, then think about tolerences and new wear rings.

    In a nutshell.... at hole shot, your impeller is pulling so hard that it literally begins sucking air from the back of your shoe where the shoe and ride plate meet (i.e. you intake is under negative pressure). Yamaha put a piece of felt there to minimize the problem, but it does not work well. It needs to be completely sealed so that the impeller pulls water rather than air into the intake. Once you get up to a certain speed, water is driven into the intake and you no longer are sucking in air (i.e., your intake is in positive water pressure). When you have positive pressure in your intake due to high pressure water, then you have the ability to make speed.

  9. #9
    Quote Originally Posted by salty View Post
    Start with the simple stuff first as advised in the previous post (Jim's performance). Remove your shoe and reseal it per instructions in the "how to and frequently asked questions" in this forum. Save yourself some money by doing this first.

    If it still cavitates after you reseal, then think about tolerences and new wear rings.

    In a nutshell.... at hole shot, your impeller is pulling so hard that it literally begins sucking air from the back of your shoe where the shoe and ride plate meet (i.e. you intake is under negative pressure). Yamaha put a piece of felt there to minimize the problem, but it does not work well. It needs to be completely sealed so that the impeller pulls water rather than air into the intake. Once you get up to a certain speed, water is driven into the intake and you no longer are sucking in air (i.e., your intake is in positive water pressure). When you have positive pressure in your intake due to high pressure water, then you have the ability to make speed.
    Picture it almost like a slipping clutch or torque converter in your car.

  10. #10
    Thanks to all you guys so this what i need to do ? I will update with results,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

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