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  1. #1

    Polaris sl780 running out of gas quick!

    Okay so I went out with my brother with our skis 780 and 750 sl's.
    We both put in 10 gallons and we ran are skis for about 3 hours and my 780 was completely out of gas and the 750 still had about half a tank it looked like.

    My 780 does run slow though. We tried taking the grey wire out incase it was in limp mode and had no luck. I am now suspecting low compression somewhere but haven't checked yet. But would this make the ski use a bunch of gas?

    The ski chugs along at about 10 mph until maybe 20 seconds and the it suddenly picks up to about 30. But will not go faster. I usually hold the throttle all the way because it goes slow so maybe that could be the issue with the gas?


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by nismooo View Post
    Okay so I went out with my brother with our skis 780 and 750 sl's.
    We both put in 10 gallons and we ran are skis for about 3 hours and my 780 was completely out of gas and the 750 still had about half a tank it looked like.

    My 780 does run slow though. We tried taking the grey wire out incase it was in limp mode and had no luck. I am now suspecting low compression somewhere but haven't checked yet. But would this make the ski use a bunch of gas?

    The ski chugs along at about 10 mph until maybe 20 seconds and then it suddenly picks up to about 30. But will not go faster. I usually hold the throttle all the way because it goes slow so maybe that could be the issue with the gas?
    It is important with the 2-stroke engines to NOT push them hard when the engine is not running properly. You risk real engine damage.

    If it is not running right, the answer is to stop riding it, not run around for three hours with the throttle pinned wide open.

    The 780 engine is quite snappy when running properly, and much faster that 30mph. Something is very wrong.

    The correct approach with these machines is to check everything. Make sure the fuel system is 100%, from tank to carbs, fresh fuel hoses, OEM fuel filter, and the carbs themselves.

    Engine compression is checked with all spark plugs out, throttle wide open. Should be within 5% of each other.

  3. #3
    Yeah i mean i have been trying a few different things so we kept going back and riding. But nothing worked. I am going to check the compression and if thats it i will replace the piston and rings. and clean all my lines and carbs. The 750 is snappy and fun. I can't even imagine how the 780 will be like

  4. #4
    Polarisitis loonatik's Avatar
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    You carbs probably have a internal leak or running way rich.

  5. #5
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    I also vote very rich.

    A simple flexible shaft LED flashlight and a look in the spark plug holes should be able to verify that, and might be only a single cylinder having problems.

  6. #6
    Do you think running rich like that will cause the loss in power? also how would i fix this problem?

  7. #7
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Quote Originally Posted by nismooo View Post
    Do you think running rich like that will cause the loss in power? also how would i fix this problem?
    If it is rich cause the screws are turned out...you turn them in.

    If it is rich cause something is broked...you fix it.

  8. #8
    Hey i just checked the compression and it reads 130 130 150 double checked with all spark plugs out and throttle wide open.

    what could have gone wrong to make the ski run rich and also if the screws are out where would they be located?

    Thanks for the help. sorry I'm new to these skis but I'm learning a lot. just installed a triple outlet on my 750.

  9. #9
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Rich on a single carb could be stuck seat, busted pieces, lots of things.

    Did you get an LED flashlight and check your wash patterns yet? This will likely answer your questions if it is indeed a rich condition.

    http://www.ebay.com/itm/Flashlight-L...item2a53aae344

    780 the screws are on the engine side of the carbs on the side facing the front of the ski.

    The high screws come with limiting cams on them to prevent the screws from being spun more than a 1/4 turn. If you run out of adjustment with them installed, you can pry them (GENTLY) off. If you do, run them in and count the turns before you go crazy making adjustments, so you can get back to where you started if you need to. I took a piece of 3/16" round stock about 18" long and ground a flathead screwdriver end on it to use to adjust these, but I still need to remove the airbox to get a good look at them.

    The lows have a T handle for adjustment, again, make note of where they are before adjusting.

    And don't assume they are all set the same, they usually aren't.

  10. #10
    Thanks for the info. Im sorry i do not understand what you mean by wash patterns.

    But i saw the T screws ill look for the high scows on the other side. which direction should i turn them to lean up the fuel mixture a bit?

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