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  1. #1

    Hole in piston of 1993 Polaris sl750 wtc

    I have a hole burnt through the piston closet to the fuel tank in my 1993 polaris 750sl water craft. I checked the carbs, they appear to be fine. I replaced the piston and put the motor back together but i am afraid to take it out on the water again.
    My water craft is stock. It doesn't have any aftermarket components. Does anyone know why a hole burnt through the piston and what i can do to prevent it from happening again?

    Thanks Nathan

  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Welcome to the Hulk!

    Click here for the 1992-1998 Polaris Service Manual.

    Unless you actually pulled the carbs apart and cleaned them, how did you check them?

    Burning a hole through a piston usually means the engine is not getting enough fuel flow at full throttle (lean burn). Need to check everything from fuel tank to the internal filters inside the carbs.

    A common upgrade for the older Fuji models is to install the triple outlet fuel pump. Search on here for more info. It guarantees proper fuel pressure at WOT.

    Also replace ALL the fuel lines, including those inside the fuel tank.

    You can find more info on here regarding other common upgrades and things to check on the Fuji engined Polaris PWC.

  3. #3
    ph2ocraft's Avatar
    Join Date
    Apr 2006
    Campbell, Ca.
    I'd also like to say WELCOME to the Green Hulk Forums!!
    After cleaning the carbs, replacing all the fuel line (including those dropping into the tank), be sure to replace that pesky fuel switch as they are famous for lean running conditions on the 93.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Welcome to the Hulk.

    Couple things to upgrade and you'll be fine I'm sure.

    New fuel hoses and filters. (be on the look out for a brass restrictor INSIDE the return hose just after the carb rack) It needs to be re-installed.

    Triple outlet fuel pump.

    Replace/ inspect the fuel shut off valve.

    Eliminate the auto cock (small fuel pump looking part) if it's still present

    Rebuild the carbs. (you already had that done, but I just post it for others to see later)

  5. #5
    Triple out put pump...diagram is on this site somewhere. Purchase form

    As an added measure I would consider going pre-mix.

    It is not an easy job, removing the oil pump, with the engine installed, but do-able. The fuel tank may have to be moved fwd alittle to rermove the oil tank. You will need to purchase a block off plate and seal it up with a gasket and sort of cement/sealer.

    Then wire in a 35 ohm resistor in the electric lines to fool the MFD to showing it is full of oil all the time.

    Piece of mind and reliability is my goal.

    Oil pumps fail , oil hoses fall off (when they do it makes a heck of a mess also)

  6. #6
    Moderated GPRXPJared's Avatar
    Join Date
    Oct 2007
    Palm Harbor, Florida
    do you have any pics

  7. #7
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by dorf View Post
    ...Oil pumps fail, oil hoses fall off (when they do it makes a heck of a mess also)
    The Polaris and Fuji oil pumps seem to be quite reliable - actual pump failures seem to be rare.

    The oil lines do need to be checked and maintained, and replaced every so many years, just like the fuel lines.

    Unless you have a bias towards pre-mix oil+gas, keeping the oil injection system for the time being is probably just fine.

  8. #8
    Here's a pic of the fuel pump routing.

    See tech section for more info on oil pump
    Attached Files Attached Files

  9. #9
    Thanks for the response. I did pull the carbs off and i got them professionaly cleaned and checked. The mechanic who is my father in Law said they were perfectly fine.

    Is installing a triple outlet fuel pump the best way to prevent this problem from happening again. How much do they cost? and is it a difficult install?

  10. #10
    THanks, i think i will leave the oil pump alone and focus on the fuel syestem and see if that will prevent my problem form happening again.

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