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  1. #1
    qbzonk's Avatar
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    Loss of top end, where do I look?

    I have a '98 GP800 that used to show 59-61mph @ 7400-ish rpms on the dream-o-meter religiously. Now she only only hits 49-51 @ 7400-ish rpms. I did the carb rebuild and still the same speed only now she eats even more fuel. She doesn't bog or hesitate, but when I check the plugs they are slightly wet, but not soaked. HS screw is 1.5 turns out from closed.

    Where did my top end go?

    I bought the ski used and haven't added much other than a few replacement parts. The ski was raced and has tons-o-mods. I have no idea what, if any, mods were done inside the motor. Here is what I know:

    F/A kit on 44mm carbs (explains some of the excessive fuel usage).
    Some type of aluminum intake.
    Premix in the tank.
    compression check revealed 130 in front 135 rear.

    prop and wear ring seem in better than good condition, no obvious knicks or dings. I checked the clearance as best I could with a straight feeler guage and I am in spec.

    There are other mods, but I don't think they would cause the problem. I have pics of almost everything if you need them.

    I have no idea why I lost roughly 8-10 mph and am still running 7400-ish rpms?

    Thanks in advance for the help.


  2. #2
    r33pwrd's Avatar
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    Look at the pump/prop area real close!

  3. #3
    qbzonk's Avatar
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    Quote Originally Posted by r33pwrd View Post
    Look at the pump/prop area real close!
    What am I looking for? If there was an issue that sapped almost 10 mph, wouldn't it be more noticeable. Would an issue here not effect rpms?

  4. #4
    Old School Never Dies! codemanrose's Avatar
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    Well ya, check the pump and impeller. If somethin is ripped or broken, it could still run the same RPMs but wont hook on the water.

  5. #5
    qbzonk's Avatar
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    Quote Originally Posted by codemanrose View Post
    Well ya, check the pump and impeller. If somethin is ripped or broken, it could still run the same RPMs but wont hook on the water.
    I looked at the pump again and the only thing I can see is a small burr on one of the fins, but nothing excessive. I'll see if I can get my camera to take a good pic of it later when I get home.

    The ski doesn't seem to cavitate or anything and hooks up just fine. The wear ring is plastic, so no chance of excessive rubbing and the I checked the clearance again and everything seems OK.

  6. #6
    RAIDER RUNNER BULLRAIDER's Avatar
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    qb....have you tried resealing the intake grate.I know I had one that lost rpm all else checked good, its worth a try.........mostly at the rear of the grate .....

  7. #7
    cheatin' piston popper addicted's Avatar
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    spray the speedo paddle wheel with silicone. you may even gain speed

  8. #8
    qbzonk's Avatar
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    I'm at work right now, I will check these things when I get home. I will try take pics of everything you guys mentioned and post them later.

    Thanks!

  9. #9
    Flying Scotsman's Avatar
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    First are you shure you lost speed,have you riden with someone who was the same speed and now your slower.
    You need a GPS to tell,the stock method is unreliable and not accurate.
    SCOTT........

  10. #10
    Old Ski Insanity w/rpm500's Avatar
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    not saying this is the case...Water laying inside the liner/hull? you said it was a race ski at one time ... water could have worked its way in over time.

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