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  1. #1

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    Is 100 lb too low for Compression

    Just for chit's and giggles i did a compresion test on my jet ski because i had no clue how many hours are on the engine. Heres what i came up with

    Assuming cylinder one is bow end

    Cylinder #1: 105 PSI
    Cylinder #2: 100 PSI
    Cylinder #3: 120 PSI


    I know for a normally aspirated engine those numbers are low. But im not too sure for a SC engine. Any Ideas?


  2. #2
    Golden Jet red fox's Avatar
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    Quote Originally Posted by PWC Newbie View Post
    Just for chit's and giggles i did a compresion test on my jet ski because i had no clue how many hours are on the engine. Heres what i came up with

    Assuming cylinder one is bow end

    Cylinder #1: 105 PSI
    Cylinder #2: 100 PSI
    Cylinder #3: 120 PSI


    I know for a normally aspirated engine those numbers are low. But im not too sure for a SC engine. Any Ideas?
    you have to rebuild the Engine head ( valves ) and check the piston ring ...

    Good luck

  3. #3
    speedskixp's Avatar
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    Quote Originally Posted by PWC Newbie View Post
    Just for chit's and giggles i did a compresion test on my jet ski because i had no clue how many hours are on the engine. Heres what i came up with

    Assuming cylinder one is bow end

    Cylinder #1: 105 PSI
    Cylinder #2: 100 PSI
    Cylinder #3: 120 PSI


    I know for a normally aspirated engine those numbers are low. But im not too sure for a SC engine. Any Ideas?
    Pretty low. Did you warm up the engine first?

  4. #4
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    The cylinder on the bow end is #3

  5. #5

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    No The engine was stone cold

    I forgot that metal expands when heated......I bet that will change things

  6. #6

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    What should stock compression on a properly warmed up 215 RXP be if everything is normal?

    I am just curious, I don't have any normal engines, and I have never measured a stock one.

    Thanks

  7. #7

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    Not only must the engine be warmed up to get an accurate reading--but the throttle must be held wide open.

  8. #8
    Water4fire's Avatar
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    135 is about right were it needs to be and that is if the timming is set for it.
    I have seen them a bit higher 140 and a bit lower 120. STOCK form!

    Your numbers still seam off for even a cold motor.

    Warm it up a bit hold the throttle wide open and try again.

    Let us know.


    .

  9. #9
    RXP305's Avatar
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    Quote Originally Posted by Louis914 View Post
    What should stock compression on a properly warmed up 215 RXP be if everything is normal?

    I am just curious, I don't have any normal engines, and I have never measured a stock one.

    Thanks

    120-135 PSI, if you have a high compression then there might be a chance that you hace some carbon build on the pistons and lower than 120 psi could have leaking valve, wear rings or maybe the time is off.

  10. #10
    GTXX's Avatar
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    don't panic about the cold numbers you have, I checked one cold and got number all over the place like that and they were within 4 psi with 6-8% leakdown when the engine was warmed up.

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