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  1. #1

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    '02 1200 GPR "missing" at WOT

    OK...my first post so go easy on me. Just picked up my first fast ski and have been lurking around the site soaking up up the knowledge, planning to add mods to get it up around 70mph. I have a Jim's FF and an 800 grate waiting to be bolted on but wanted to get a baseline speed first, expecting 60-64mph. Well, it seems that there is an issue. Top speed on a GPS is 50mph..imagine my disappointment (pretty hilarious actually). At WOT, smooth lake, I can feel the ski try to surge to a faster speed but only briefly and then it settles back to 50mph, very briefly it popped up to 58mph and then settled back to 50. No other symptoms as far as I can tell.

    The ski has 172 hrs and had the following mods performed at 168hrs: topend rebuilt with SBT cylinders and pistons, carbs rebuilt, Riva SS Cat kit and chip.

    So I pulled the plugs and the rear plug was wet and black while the other two seemed normal and were a nice light brown color. Compression front to rear is 124/122/137, I thought the 137 seemed odd...

    We replaced the plug wires and the results did not change. I am not a very experienced wrencher so how do we determine if it is an igintion or fuel issue?

    I sure appreciate any advice.


  2. #2
    TRIPLE PIPES ARE 2-STROKE TURBOS allcool's Avatar
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    Do a compression test with your valves open and closed.

    Disconect the power wire plug to the power valve servo motor.

    Turn the power valve cable wheel all the way one way, do a comp test.
    Then turn the wheel all the way the other direction, do another compression test and tell us what you get.

    allcool
    Last edited by allcool; 09-22-2007 at 02:13 PM.

  3. #3
    Moderator RX951's Avatar
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    welcome to the forum

  4. #4

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    Thanks guys. I should be able to post the comp test results monday.

  5. #5
    WATER WOODY's Avatar
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    Welcome to the forum

  6. #6

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    I had a shop run the test with their gauge as you described and the readings were the same with valves open and closed. 105/105/110

    The quality of my gauge may account for the differences between these numbers and the numbers that I recorded.

    Do these numbers seem about right?

    goestooslow

  7. #7

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    Good Afternoon guys! Do these compression readings of 105/105/110 with valves both open and closed offer any insight or eliminate possible causes?

    goestooslow

  8. #8
    TX21's Avatar
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    Quote Originally Posted by goestooslow View Post
    Good Afternoon guys! Do these compression readings of 105/105/110 with valves both open and closed offer any insight or eliminate possible causes?

    goestooslow
    Stock I got 120 psi on all three after the rebuild. I think thats what its supposed to be.

    Shoulda bought mine homie. I am just a few hours away and mine runs likea champ! With some R+D heads I get #137 ish on all three.
    Last edited by TX21; 09-25-2007 at 04:27 PM.

  9. #9
    WE DONT DIAL 911 RDH's Avatar
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    Quote Originally Posted by goestooslow View Post
    Good Afternoon guys! Do these compression readings of 105/105/110 with valves both open and closed offer any insight or eliminate possible causes?

    goestooslow

    thats a good difference of numbers although a little low... the valves open should produce less pressure than closed,,, i hope the shop knows what their doing... also the 3rd cylinder on stock heads is .5cc smaller than 1 and 2 so it should be getting the lowest reading

  10. #10
    My son (mohawk man) jeffsntx's Avatar
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    1. Do you know what prop is in the ski? Someone could have changed it and gone way too steep with the pitch.

    2. Did you look at the tachometer to get some sort of RPM reading at WOT?

    3. The SBT cylinders will keep you from reaching the speeds that a lot of people see because they are sleeved.

    4. RDH is correct. The compression should have been a little different when you compare valves open vs. valves closed.

    5. Have you looked in the fuel filter to see if you can see any water or debris in it?

    6. How fresh is the fuel that is in the ski? Has it been sitting for a while? Did you fill up at a marina?

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