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  1. #1

    Question Carb tuning questions? 94' polaris sl 750

    Ok I took my ski to the lake this weekend and am having issues.

    (1)First issue would not start. Almost killed battery trying to start.
    (2) Finally got started by giving 1/4 throttle and it smoked bad and would not stay running.
    (3) Would not rev up was only getting 1/4 throttle about 2,000 RPM(if my gauge is right)

    I am thinking that my carbs are out of adjustment.

    It started after about 15 minutes last time I rode three weeks ago .


    OR is there something else I should be looking at first???

    Any help????


  2. #2
    Moderator beerdart's Avatar
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    Welcome to the Hulk..

    Its sounds like you have a fuel delivery problem.
    Have the carbs been rebuilt/cleaned lately?
    What is the history of the Ski?

  3. #3
    seaobin's Avatar
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    sounds like the carbs need cleaned

  4. #4
    Not sure of the whole history of the machine have only had it since the beginning of august.

    It has been rebuilt but thats about all I know.
    The oil tank has been taken off and we mix the oil ourselves.

    I have read about the triplett fuel pumps are these expensive and something I should look into?

  5. #5
    seaobin's Avatar
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    $40 and a requirement, or you will destroy the engine. Have you checked the compression yet. If you have a holed piston, you wont get pulse pressure, and hense no fuel delivery

  6. #6
    FLjoyrider's Avatar
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    Quote Originally Posted by skmpmm2002 View Post
    Ok I took my ski to the lake this weekend and am having issues.

    (1)First issue would not start. Almost killed battery trying to start.

    Do a compression test

    (2) Finally got started by giving 1/4 throttle and it smoked bad and would not stay running.

    Clean the carbs

    (3) Would not rev up was only getting 1/4 throttle about 2,000 RPM(if my gauge is right)

    Make sure you are mixing your fuel right.. something like 40:1 will probably be good.

    I am thinking that my carbs are out of adjustment.

    It started after about 15 minutes last time I rode three weeks ago .


    OR is there something else I should be looking at first???

    Any help????
    Sounds like the fuel / oil mixture is off

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk.

    Try priming the carbs with a little premix to get it to start easier.

    Check the carb settings and make sure they are set for your specific model year.

    Triple outlet fuel pump is a good idea, along with new fuel hoses, clean and inspect the petcock, check the fuel filters, and clean/inspect the carbs thoroughly.

  8. #8
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    And if you still have item #4 in the diagram (94 models came with it) get rid of it, and plug off the vacuum port for it on the intake.


  9. #9
    johnsonmtz's Avatar
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    Quote Originally Posted by starflight View Post
    And if you still have item #4 in the diagram (94 models came with it) get rid of it, and plug off the vacuum port for it on the intake.
    I'm getting my list lined up to rehab my recently acquired '94SLT750. I've read that the autocock must be deleted from the fuel system in addition to the triple outlet pump upgrade.

    But, what on earth does the autocock do anyway? I've never really heard an explanation of the purpose for this little troublemaker.

    Please enlighten those of us trying to keep these skis running

    KJ

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow Why should the auto-cock be deleted - what was it for, anyways?

    Quote Originally Posted by johnsonmtz View Post
    ...I've read that the autocock must be deleted from the fuel system in addition to the triple outlet pump upgrade.

    But, what on earth does the autocock do anyway? I've never really heard an explanation of the purpose for this little troublemaker.

    Please enlighten those of us trying to keep these skis running
    My understanding is that the auto-cock valve was supposed to prevent fuel from dribbling through the carbs and into the engine intake when the engine was off, and the ski was sitting for an extended time period.

    The auto-cock valve is supposed to open the fuel flow when it senses crank case pulse/vacuum, and close the fuel line when the engine is not running.

    Sunshine and weather can increase the air pressure in the fuel tank, and force fuel past the carbs into the engine.

    The problem, as I understand it, is that the auto-cock itself would internally be a fuel flow restriction, and not allow full fuel flow to the carbs when the engine was running at WOT. This can cause lean burn piston damage.

    So the Polaris solution is to delete the auto-cock device, and have the rider remember to always use the fuel shut-off knob when you are finished riding for a while.

    Of course, if the owner is good about always shutting off the fuel selector valve/knob, there is no problem with fuel being forced through the carbs.

    If the fuel selector is left turned on, and the fuel tank air pressure vent happens to stick closed (no pressure release), the heat from the sun can create enough tank pressure to flood the engine with liquid fuel while it is sitting.

    Note: Polaris revised the fuel tank venting system several times. Those with earlier 1992-1994 models might want to replicate the 1995 fuel tank vent system, which uses two separate fuel tank vent valves - one for excess air pressure release, one for vacuum release.

    We have heard from a few GH members who left the fuel selector valve ON that they later discovered the engine was completely full with liquid gasoline when they returned to it.

    Not only is this a major fire/explosion hazard, but there is also a real risk of hydro-lock damage if the engine is cranked while there is a lot of liquid fuel inside.

    Recommended practice;
    - Remove the auto-cock, and properly cap off the un-needed connection to the engine.

    - Always turn off the fuel selector valve when you are done riding for a while

    - When the machine has been sitting for a while, always lift the seat and smell for gasoline, and look for fuel/water leaks or other potential problems, before you start the engine

    - Make sure the fuel selector valve is in good condition, and does not have any air leaks.

    The fuel supply lines are under suction from the tank to the fuel pump, so any leaks at the selector valve will leak air into the fuel line, not fuel out into the hull.

    The selector valve can be rebuilt with a frewsh and lightly greased O-ring, or replaced with a new one from Yamaha;
    Where can I get a replacement fuel selector valve (On-Off-Reserve)?

    If your fuel selector valve is leaking air into the fuel system, you will have problems. Refurbish the valve seals, or replace the valve.
    The ON-OFF-Reserve Polaris fuel selector valve 7052063 is no longer available, but the 1995 Yamaha Wave Blaster Fuel Selector valve may be a good replacement (PN 6K8-24500-02-00)

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