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  1. #1

    95 sl750 rebuild?

    Hey I'm new to this site and new to 2 stroke motors and was wondering if anybody could help me with my ski? I tried searching for my problem on this site already but couldn't find anything, maybe I'm not looking good enough or something.

    But anyway I have a 1995 Polaris SL750 that I recently bought, rode it maybe 5 good times this summer and had no problems out of it. Well I took it out one day (GRADUATION DAY of all days) and it just cut off after riding it for about 3 hours. I wasn't riding it any different than normal, and I would take a break every now and then to let it cool down.

    Well after trying to crank it back up for a while, we gave up and went inside. The next morning me and my friend went outside to take a look at it and the oil tank was almost full!? It ran fine the whole time we rode it the day before. And every other time I've rode it, it would use a good amount of oil so I knew something was wrong so we didn't try cranking it up again.

    Next thing I did was bout a oil pump block off kit so i could premix the gas and be sure it was getting oil. Well we got that on and guessed about how much gas was in the tank, poured the appropriate amount of oil in plus a little bit more, and shook the gas tank up to make sure it mixed.

    We hooked the jet ski up to a water hose and cranked it up to check for leaks with the oil pump block off and to see if it would run normal, well it sounded almost fine idling but if you gave it any amount of throttle it would become super loud making a sort of high pitched knocking/tapping noise. We let it run for about 5 minutes and then cut it off.

    Today I bought a compression tester from a parts store and checked the compression, I've seen that it should be somewhere around 140-150 psi right? well my front cylinder was 118, middle cylinder was about 119, but the cylinder farthest to the back was 60
    I know 60 is too low but are the other two that low just because of wear and tear over the years. The MFD reads 45 hours and the motor seems really clean and the ski is in good shape for a 95, (i think). Can anybody give me any advice, is this engine trash or in need of a rebuild? If i rebuild it what all is involved with it? And about how much would a shop charge me to rebuild or replace the motor. I found the motor for $695 on sbt and a top end rebuild kit also. Any help is good, and thank you in advance. This website seems really good so I know someone will be able to help me thanks guys.

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

    When you checked compression did you hold the throttle wide open with all spark plugs out?

    I would start by removing the cylinder heads and visually examining each piston and cylinder.

    If you can post some clear photos we can help you diagnose what caused the failure. From there we can determine whether you need an entire engine rebuild or just a top end refresh.

  3. #3
    No i didn't hold the throttle wide open, should i have?

    That was going to be my next step thanks, I'll try and get on that today and get a few pictures if i don't get home too late, thanks K447 for the quick response.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by jamestfraley View Post
    No i didn't hold the throttle wide open, should I have? ...

    Compression testing is all about how well the piston is compressing the air into the cylinder. With the throttle closed you are starving the engine for air during the test. Less air means lower compression number.

    Retest test with throttle held wide open.

    And all spark plugs out. You want maximum cranking RPM during the compression test. If some spark plugs are still installed it slows down the engine cranking, which can reduce the compression readings.

    And of course the battery needs to be strong. A weak battery will spin the engine less quickly, resulting in lower numbers.

    Compression testing in the described manner also makes for consistent test results each time. The only variable is your actual compression gauge. Use the same gauge each time and you can compare numbers and detect a change in the internal health of the engine.

  5. #5
    Ok thank you I'll do that tomorrow, I had all the spark plugs out and the battery was strong but I'll do it tomorrow with the throttle open, thanks.

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