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  1. #1

    1997 polaris sl 780 Accelaration Problem

    Hi guys,

    my polaris accelerates very slugish but when at the throttle isn't responsive at all but when it respondes the speed is ok.
    my dad had it for a long time he bought it new 13-14 years ago had 40 hours on the clock he said it wasnt responsive since day one.
    I fully restored the ski changed all fuel lines rebuilt the carbs changed the mountings and all What do i have to look for?
    thank you very much
    sorry for my bad english im from the eu


  2. #2
    BlueFishCrisis's Avatar
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    Take a look through this, Post #13 http://www.greenhulk.net/forums/show...t=15473&page=2

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Have you looked at the engine itself?

    Cylinder compression?

    Checked the intake reeds?

    Correct spark plugs?

    What is the maximum sustained RPM while running on the water at full throttle?

    What about the jet pump? Inspect for proper sealing between the hull and the ride plate, the pump base and the water intake area. Any sealing gaps or air leaks will reduce acceleration and thrust from low speeds.

    Where are you located?

  4. #4
    The engine has 40 hours on it is in perfect shape inspected it when i took it out to replace the mounts looks perfect.

    Cylinder compression is 147 148 150

    Reeds are in perfect condition

    Spark plugs : B8ES

    RMP: no idea mfd is broken

    Jetpump was refurbished by a metal worker the clearince is 0.08 if im not mistaken he changed the material since the housing was pressing on the impeller

    Location : Malta

  5. #5
    BlueFishCrisis's Avatar
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    97 SL 780 plugs should be BPR8ES. Impeller to wear ring clearance service limit is .02. I provided a link to check your carb settings and to go through basic tuning guidelines. IF everything else is perfect as you say it is, and you have verified spark on all cylinders with a spark tester, then the carbs need attention. Factory needle settings are Highs 1/8 out, lows 1 1/4 out. Pop off set at 20-24 PSI.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Polaris sl 780 View Post
    ... Spark plugs : B8ES

    RMP: no idea mfd is broken

    ...
    Those are not the correct spark plugs, as I recall. They need to be Resistor type spark plugs

    If MFD is not working, and the fuse inside the electrical box is good, then disconnect the MFD at the connector on the back of MFD. A dead MFD can cause ignition problems.

    MFD uses a 0.25 Amp fuse, not higher.

  7. #7
    [QUOTE=K447;2180230]
    Quote Originally Posted by Polaris sl 780 View Post
    Factory needle settings are Highs 1/8 out, lows 1 1/4 out. Pop off set at 20-24 PSI.
    wgat does 1 1/4 mean ? how do i set the carbs sorry new to setting carbs :S

    Spark is on all cylinders i did check with a spark plug tester

    Thats chinese to me what does that mean ? thank you

    does it make that much difference that it has to be a resistor type spark plug? then i shall change them.

    i changed the fuse so its good 0.25amp 250 volts

  8. #8
    BlueFishCrisis's Avatar
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    The resistor type plug should make a difference, and the projection tip increases the temperature of the plug. The resistor removes radio interference in the system and as a byproduct reduces the voltage at the tip. Not saying that this is the or a problem, but should run the correct plugs to remove it from the equation.

    1 1/4 means to take the low speed screws and close them (tighten into the carb body) until they are lightly seated and will not easily turn any more. Then open them 1 1/4 turns out. This is your starting setting. Same with the highs.

    The tuning tips describes sluggishness as two different types. One where the ski falls immediately flat on its face and dies, the other where it keeps trying to run while gurgling on fuel. The first is a lean condition, the latter a rich condition. Read the write up to fully understand.....

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