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  1. #1

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    Question 1995 slx 780 running issues

    Hi, new here. Anyway i have a 1995 polaris slx 780, it wasnt running when i got it. I checked spark and had very little to none so i replaced the spark plugs and wire boots and had great spark after that and got it running, when it fired up (out of the water) it looked like it dumped alot of fuel, oil, water out of the back?? But it did it that one time. I took it on the lake and it did pretty good, but it smoked quite a bit on start ups and went through gas quickly. Id say a little over an hour of use and it would run out (mfd doesnt work) i always go out when my mom takes her boat so she can rescue me with a can of gas  but last time i had it out it was fine and i was on it most of the day, then it ended when i went up a wave, came back down and it quit and when i tried to start it it just clicked. So got it home was looking at stuff and realized the drive shaft was disconnected tightened it back up and tried to start it and it turned over and started. Next lake day took it out and it started like it normally does and ran okay for a short time then lacked power and eventualy quit and then it would just click when i hit the button. Ive retired it for the season and have been riding my other 95 sl750 wich does amazing, good power easy on gas ect. But im kinda thinking i have a cylinder/piston issue, i have not check compression yet.. but im not 100% as these are my 1st skis and looking for suggestions? Oh last thing i noticed was the fuel water separator looked dark like it had oil in it, but the fuel filter ( it was replaced b4 i got it and its clear) located before the cut off valve is clean? Any info is appreciated!!


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk.

    Where to begin?

    1st, these skis doesn't guzzle a lot of gas. A tank full should run for hours of use. Even at WOT. Make sure you don't have a fuel leak. A leak inside the ski can lead to an explosion.

    If you're not leaking from the fuel tank or hoses, you have a large amount of fuel going through the carbs and out the exhaust. Which you may have already indicated in your post.

    You might have fuel leaking past the needles and seats. You might have broken reeds. You may have way too big jets installed into the carbs. Although you would generally have performance issues if any of these conditions were occurring.

    Ahh the infamous I hit a wave and it quit issue.... First thing to check is if the battery shorted to the elec box. Next would be to inspect the ground wire connections. I'm not sure why, but try adding a ground wire from the elec box ground connection to the intake manifold stud. This seems to get people up and running.

    Drive shaft was disconnected? This has me puzzled. The drive shaft is splined and fits inside the engine coupler and the impeller inside the jet pump. There is no way for it to disconnect. Need better explanation on this.

    Compression test is always good. Make sure to hold the throttle open when conducting the test.

    Oil cannot get into your water separator without it being in the fuel tank. Maybe you got some old fuel?

    And what fuel filter are you talking about? The water seperator should have a stainless mesh fuel filter integrated into it. Any in-line filter was added and should not be there.

    Pictures please.

  3. #3

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    Thanks for the response!

    Yeah i didnt think the amout of gas it was using was right because my other sl750 last pretty much all day, I only put gas in it cuz my mfd doesnt work and im just being cautious, but i never have to completely fill it up just a few gallons maybe 1/2 a tank. But my 780 thats giving me trouble, when it runs out i have to fill it up around 9 gallons.

    I dont see any fuel leaks, nor do i have a fuel smell under the seat when i remove it, so im thinking what you said about fuel leaking out of my exhaust due to a carb related problem makes sense, i just cant see it when im in the water 😅 so carb rebuild will next on the list, after a compression test. (Hoping i dont find poor compression)

    Have not checked my battery cables/ connections so ill def. Do that, i know it has the plastic batt cover but it could have moved out of place possibly.

    My driveshaft was threaded or screwed on to the crank shaft? I will get some pictures of where it came loose, also some pictures of the fuel filters so theres a better understanding of what im seeing, its just raining like a s.o.b. where im at r.n. so as soon as it clears up i will get some

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Your drive shaft is splined and goes into the engine coupler on the engine side. I'm assuming that came unthreaded somehow. That would kind of make sense, but I've never seen one actually loosen up before.

  5. #5

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    Sorry im just getting back to this, but here are some pictures of what im seeing

    Click image for larger version. 

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ID:	478260 so this is the two filters in mine 1 before the shut off valve, other is what i assume is the water separator

    Click image for larger version. 

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ID:	478261 this is the black colored fuel...with what i assume is oil and dont think thats normal

    Click image for larger version. 

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ID:	478262 and where the red arrow is pointed is where the drive shaft came unthreaded from

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Ditch the in line fuel filter. Was not used by polaris and is not needed.

    The water seperator has a fuel filter installed into it. Yours is sitting on the bottom of the fuel bowl though. It should be pressed onto the top aluminum piece. Correct that by pushing the SS filter up onto the nipple.

    The black fuel is odd. Most likely a lot of 2 stroke oil mixed in. I'd play it safe and drain the fuel tank of anything in there and start out with fresh fuel.

    1. Is the oil pump still installed under the carbs? It's possible the previous owner removed it and is running premix fuel/oil.

    2. The engine coupler is what came undone. It is supposed to be torqued pretty good, so that doesn't happen again. You need to hold the PTO piston in place when torquing the engine coupler. I like to bring the piston to near Top Dead Center with the spark plug removed. Then I feed a bungee cord down the plug hole to take up the space between the head and piston. That should hold the piston in place while applying pressure to the coupler.

  7. #7
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by xlint89 View Post


    The water seperator has a fuel filter installed into it. Yours is sitting on the bottom of the fuel bowl though.
    … push… the SS filter up onto the nipple. …
    While he is in there, check the condition of the TWO o-rings. The large one that seals the water separator lid and the much smaller o-ring that fits inside the top of the metal filter canister.

    Click this link to find lots of Polaris PWC info.
    Somewhere in there I think the water separator o-ring sizes are specified or linked to.
    http://polarispwcknowledge.shorturl....t-things-to-do

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