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  1. #1

    Ok new numbers still not good though

    Granted it was very hot today and a little ripple in the water so maybe in current configuration I could get a few MPH but its still not where it should be I think.

    OK this is a GP1200 1998

    Flame arrestors, primer kit, R&D intake grate, R&D ride plate (shimmed), brand new pump liner and newish stock impeller.

    Ran 6750 RPM (Tiny Tach) and 51MPH (GPS)

    I figure I am losing about 7-10 MPH somehow. THe ski starts and runs good and engine seems to be strong.

    I didn't tune the carbs much because it was getting late and the water was a bit rippled but I don't think it will get much better from carbd tuning.

    Also if I don't have the rideplate shimmed down then it used to porpoise like crazy. I can try a go without the shims again with the new liner and prop but I think its going to porpoise too much.

    What do you guess think. I think I am getting good RPM, right?


  2. #2
    Flying Scotsman's Avatar
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    Impeller/shims in rear.

  3. #3
    Flying Scotsman's Avatar
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    Make sure you have spark at all 3 plugs as well.

  4. #4
    Mpeavler's Avatar
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    Shimmed down....will cost you big MPH also

  5. #5
    I guess I'll try with some shims taken out and see the difference.

  6. #6
    krispaintballz's Avatar
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    Your ski shold be running stock 56-58 with no problems.

  7. #7
    I actually gps'd my stock 99 gp1200 at 63 mph. My dad's will run about 58 maybe more with the new impeller and breathers.

  8. #8
    Flying Scotsman's Avatar
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    Quote Originally Posted by Flying Scotsman View Post
    Impeller/shims in rear.
    Quote Originally Posted by Flying Scotsman View Post
    Make sure you have spark at all 3 plugs as well.
    Quote Originally Posted by Mpeavler View Post
    Shimmed down....will cost you big MPH also
    You should look at your IMPELLER and if you have shims in the rear loose them they slow you down.
    Its hard to shim a stock plate by shimming in front without compromising the plate.

    A stock 99 should run 61 mph or more.

  9. #9
    Quote Originally Posted by Flying Scotsman View Post
    You should look at your IMPELLER and if you have shims in the rear loose them they slow you down.
    Its hard to shim a stock plate by shimming in front without compromising the plate.

    A stock 99 should run 61 mph or more.

    Thanks for the replies. Like I said I just put in a new liner and used but good shape impeller.

    I only shimmed the rideplate before because it was porpoising like crazy. I ride only in bays and ocean and it is almost never flat calm. With just a tiny ripple I could not even get a top speed run as it was porpoising so much. After I shimmed the plate I noticed that I was overrevving >6900 RPM at half throttle so I knew the pump liner/impeller where in bad shape.

    Now I will try pulling some of the shims out but I don't want to start porpoising again. SO how much should I shim this plate?

    I think if I put no shims in its just going to bounce too much again....

    I know the best way is to test and tune but I have to pull this ski on and off a trailer everytime I need to make an adjustment so getting it close the first time and then fine tuning the second would work better for me.

    SO what do you guys think I should start out with? Right now I have the back shimmed about 1".

  10. #10
    Adam's Avatar
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    Quote Originally Posted by ucf_motorcycle View Post
    Thanks for the replies. Like I said I just put in a new liner and used but good shape impeller.

    I only shimmed the rideplate before because it was porpoising like crazy. I ride only in bays and ocean and it is almost never flat calm. With just a tiny ripple I could not even get a top speed run as it was porpoising so much. After I shimmed the plate I noticed that I was overrevving >6900 RPM at half throttle so I knew the pump liner/impeller where in bad shape.

    Now I will try pulling some of the shims out but I don't want to start porpoising again. SO how much should I shim this plate?

    I think if I put no shims in its just going to bounce too much again....

    I know the best way is to test and tune but I have to pull this ski on and off a trailer everytime I need to make an adjustment so getting it close the first time and then fine tuning the second would work better for me.

    SO what do you guys think I should start out with? Right now I have the back shimmed about 1".
    Is that 1 inch down at the rear of the rideplate ? If so, that way too much! Put a straight edge from the intake grate back to the rear of the rideplate ,it should be parallel with the flat of the intake grate. This will help with the speed while helping to stop the bouncing.

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