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  1. #1

    HELP NEEDED: Polaris sl750 smoking

    Hello everyone,
    Im new to the forum and to jet skis but not to working on engines.
    I bought two skis from a man who swore to me they both ran but didn't start them for me since he didn't have the hose adapter for a great price.
    I got the sl750 started with some starter fluid and ran it through the hose. Oil was seeping through the spark plug holes and there was a huge cloud of white smoke just pouring out of the exhaust.

    I did not check the compression but i suspected the piston rings were worn so i tore the engine down and the pistons/rings/rods/and crank look to be in great condition as if there was a rebuild.
    the 3rd piston housing has a 2 marking on it so this is telling me there was deff a rebuild.

    So i want to replace the rings and put the engine back together but i am not sure if they had the walls honed out and went with over sized piston rings or not. The piston rings on there now are marked N25.

    What do you guys think i should do?

    Thanks,
    -Cori


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    It is OK to start and run these engines from cold for 20 seconds or so without cooling water. Starting fluid is hard on the engine. If it will not start with just gasoline, something is wrong.

    Make sure the correct NGK spark plugs are installed. There should be no seepage of any kind from around the spark plugs.

    Why would you tear the engine apart and not check compression first?

    See my signature links for lots of useful info and recommended maintenance.

    The piston diameter must match the cylinder diameter, minus the specified piston to cylinder clearances. Rings are matched to the piston. Oversize pistons use oversize rings, matched to the same size spec.

    If you do not have the equipment to properly measure the cylinder and piston diameters then you can take them to an engine machine shop.

  3. #3
    gp1200rider's Avatar
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    Welcome to the forum,
    Sounds like it just had been sitting for a long while smoke bomb pretty normal for first fire up on a 2smoker . clears out after a ride, I would of checked compression first. pistons should be marked on top if there oversize clean them with gum cutter. if its been sitting for a long time RBLD the carbs and replace the fuel lines. pics would help of cyl & pistons I hope you marked them all per cyl etc

  4. #4
    Well i just jumped to conclusion and started to take things apart lol After the first shot of starter fluid it start up fine after that with no fluid needed. Idled good. The ski sat for 1 year since the person i bought it from had it and it still had the 2012 registration stickers on it so idk how long they have been sitting. I will show you some pictures of how everything looks.

  5. #5






    Okay here are the pictures of the pistons. Do you see any markings that indicate a overbore?

  6. #6
    The cyl walls look good and my plans are to replace the rings and put a triple output fuel pump on it along with new lines and change the oil.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by nismooo View Post
    ... my plans are to replace the rings and put a triple output fuel pump on it along with new lines and change the oil.
    This is a 2-stroke engine. There is no liquid oil reservoir inside the engine.

    If the factory oil injection system is still present then the engine slowly pumps 2-stroke oil from the external oil tank and dribbles the oil into the engine intakes at the carburetors. The oil coats the engine crankcase internals and eventually gets drawn up into the combustion chamber where it gets burned with the gasoline.

    What model year is this watercraft? Last two digits on the HIN number plate on the rear deck.

  8. #8
    BlueFishCrisis's Avatar
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    Quote Originally Posted by K447 View Post
    Last two digits on the HIN number plate on the rear deck.
    I am going to guess 94, although the motor kinda looks like a 93.......

  9. #9
    Wow thanks for the info guys. Now i wish i came on here first before taking apart a perfectly fine motor.
    The last four digits ar C494

  10. #10
    its a 1994 jet ski polaris sl 750

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