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  1. #1

    95 Polaris SL 750 power issue

    When I got this ski used.....it started but revved way hi.

    So it was identified that throttle cable was tight. Adjusted it and ran it while it was hooked up to water hose. Of course I left water hose on too long. Now its hydro-locked.

    So uncorked the cylinders and got it dried out...(ether and mixed gas poured into cylinders) and it started and ran....idled. adjusted the carbs...

    Got it on the lake and fired it up....ran great for half a lap (5 minutes).....yay......then blaaaaaaaaaah. Dogged out. It starts, idles, runs at a low speed.....but it wont crack open.

    So I checked it all out......Has spark, fairly dry plugs, changed out fuel pumps (impulse), cleaned out fuel bowl, checked fuel filters, added 3 gal fresh 91, sea foam, 1 pint 2 cycle, fuel tank not vacuumed. back in lake....blaaaaaaaaaaaaaaah.......

    I checked out the water jet intake after a load of weeds got stuck in there....looks clean now. The over heat cable has popped off and I taped it back on.

    Can this be the result of a bad stator? What else could it be? Does ANYONE have any clues??


  2. #2
    johnsonmtz's Avatar
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    Quote Originally Posted by matala View Post
    started but revved way hi......throttle cable was tight. Adjusted it....

    ran it while it was hooked up to water hose. Of course I left water hose on too long. Now its hydro-locked.

    ....got it dried out...started and ran....idled. adjusted the carbs...

    Got it on the lake and fired it up....ran great for half a lap (5 minutes).....then dogged out. It starts, idles, runs at a low speed.....but it wont crack open.


    Has spark
    fairly dry plugs,
    changed out fuel pumps
    cleaned out fuel bowl
    checked fuel filters

    Can this be the result of a bad stator? What else could it be? Does ANYONE have any clues??
    Does the MFD work? What max RPM are you getting? That ski should see about 6200RPM. An engine that runs extremely high RPM at idle can be a lean engine.

    Have you checked compression on all 3 cylinders? Honestly an engine that "....ran great for half a lap (5 minutes)......then dogged out....." sounds like a classic lean burn down. A lean engine will run great for a bit until the piston finally gets hot enough to start melting.

    So when you hydrolocked the engine, was it running when this happened or you just tried to start it and realized the cylinders were full? It's possible if the hydrolock was hard enough that the crank could have been thrown out of phase, which in turn throws off timing = Lack of Power.

    A bad stator might cause this. You can search forum, there have been topics on stators where you can find specs and tolerances for the individual wires.

    What fuel pump was on the ski and what did you install in it's place? Back to my previous thought, this really sounds like you starved a cylinder for fuel and you have a lean burn. The 750's really do need the 3-outlet fuel pump retrofit. With that these are very reliable engines.

    What adjustments did you make to the carbs?

    Another possibility is the jet pump bearings have gone bad. If you run these engines on a hose for a long time the bearings can overheat and cause damage.

    The sequence for running the engine on a hose should be: Start engine, turn on water source......run for no more than 30 seconds....turn off water source, shut down engine.

    KJ

  3. #3

    95 Polaris SL 750

    Thanks for your imput.

    First...the LCD does not work so I dont know how many RPMs. Not sure what the MFD even is.

    I have not checked compression. I will

    The engine was full of water and OFF when tried starting it. So the crank being out of time is an idea.

    I have an identical twin 750 to rob parts from. Attached is the fuel pump style changed out.

    I actually had someone else adjust the carbs...but he aligned the carbs along the spring rod and seated the jets.

    What symptoms come from bad jet pump bearings? It did kond of rattle back there when I first got it started after the cable adjustment was made.

    It just ran for less than 30 seconds with the water hose hook-up...several times of course to blow the water out. My pal did that move.....leaving the water on.

    So..the lean-burn cylinder compression test is the first thing to check?

    Thank you once agian!!
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  4. #4
    johnsonmtz's Avatar
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    Check compression first.

    That is a stock single outlet fuel pump. You need to get a 3-outlet pump, which actually has 5 hose fittings; 1 for pulse, 1 for fuel inlet, and 3 for fuel outlet.

    These skis rattle a good bit while out of the water but once the pump loads with water they quiet down.

    KJ

  5. #5

    95 Polaris SL 750

    Thank you. So then each carb has a direct line then?

    Compression test showed the first cylinder had the melt down...same one as my other 95. I need to replace the piston.

    Can I swap out the middle jug .....entirely .... from my parts ski......to replace the third on my newer one? Will it fit?

    What causes the lean burn out on that cylinder? Should I just premix?

  6. #6
    johnsonmtz's Avatar
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    Quote Originally Posted by matala View Post
    Thank you. So then each carb has a direct line then?

    Compression test showed the first cylinder had the melt down...
    Can I swap out the middle jug .....entirely .... from my parts ski......to replace the third on my newer one? Will it fit?

    What causes the lean burn out on that cylinder? Should I just premix?
    Yes, each cylinder has it's own individual feed line from the fuel pump. If you look in the tech section you'll find an image file that shows the proper routing of lines and which hose connections to cap off for the 3-outlet fuel pump.

    The MAG cylinder burning a hole is the classic sign of a worn out single outlet fuel pump. Pre-mix oil has nothing to do with a lean burn condition. Your burned cylinder has everything to do with poor fuel delivery and nothing to do with oil supply. However, while you're doing some maintenance, I would suggest you run new oil lines and make sure all the clamps are snug.....just to be on the safe side.

    A 750 is a 750 so yes, if you have a good cylinder and piston on another ski you can certainly transfer that to your dead engine and get back running.

    KJ

  7. #7
    I see KG....so a new 3 outlet fuel pump, new oil delievry lines with clamps should cure the lean burn that has plaugued both skis. The fuel line as it is off a single outlet fuel pump has to send fuel off of the one line and pass along all three carbs while the three outlet is a direct feed.

    Good to know that my highest compression middle jug will fit in place of my shot third.
    aybe it will be back in action yet this summer. Thanks for your help man!!!

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