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  1. #1
    RiverRat71's Avatar
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    255 Compression Numbers???????

    Hi all, just replaced plugs in my 08 255 & decided to do a compression test, first since buying ski new. Cylinder #1 160, #2 160, #3 150. These numbers are with a Might Vac gauge (decent quality), fully charged battery, engine cold with plugs in. I was a little surprised to see #3 that far off. I know 10% is the acceptable variation but this machine has been maintained with no expense spared & to the "T" since day one. It does have 125 hours now but the oil has never even changed colors & the plugs always look beautiful at every change. Fresh water ridden all it's life. What gives? RR


  2. #2
    ABBOTT's Avatar
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    Should be fine. There's usually always one that's off like that. Ride it like you stole it, those are decent psi's.
    On a different note (and someone correct me if I'm mistaken), number 3 is usually the one that sits a little lower than 1 & 2. Mine always have as well.

  3. #3
    RiverRat71's Avatar
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    Quote Originally Posted by ABBOTT View Post
    Should be fine. There's usually always one that's off like that. Ride it like you stole it, those are decent psi's.
    On a different note (and someone correct me if I'm mistaken), number 3 is usually the one that sits a little lower than 1 & 2. Mine always have as well.
    Thanks for the reply. I am not real concerned just kinda surprised. This machine has always ran flawlessly. I have to say the most reliable out of the toys I have had.

  4. #4
    Eastside Powersports Slow 91's Avatar
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    start up the ski and let it warm up and then retest. although those numbers are fine.

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  6. #5
    RiverRat71's Avatar
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    Quote Originally Posted by Slow 91 View Post
    start up the ski and let it warm up and then retest. although those numbers are fine.
    That is what I plan to do. Just spoke with a very good mechanic friend of mine & he said the exact same thing. RR

  7. #6
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by RiverRat71 View Post
    Hi all, just replaced plugs in my 08 255 & decided to do a compression test, first since buying ski new. Cylinder #1 160, #2 160, #3 150. These numbers are with a Might Vac gauge (decent quality), fully charged battery, engine cold with plugs in. I was a little surprised to see #3 that far off. I know 10% is the acceptable variation but this machine has been maintained with no expense spared & to the "T" since day one. It does have 125 hours now but the oil has never even changed colors & the plugs always look beautiful at every change. Fresh water ridden all it's life. What gives? RR
    Good numbers! Retard the cam slightly to drop the numbers to 140.

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  9. #7
    RiverRat71's Avatar
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    Quote Originally Posted by 1tommygunner1927 View Post
    Good numbers! Retard the cam slightly to drop the numbers to 140.
    Thanks Tommygunner but I would be getting in over my head. I do most of my service & all of my mods but I am not a mechanic.

  10. #8
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by RiverRat71 View Post
    Thanks Tommygunner but I would be getting in over my head. I do most of my service & all of my mods but I am not a mechanic.
    Understood! The best line in all of the Clint Eastwood movies: "A man has got to know his limitations".

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  12. #9
    Sanfish's Avatar
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    This is only a 6% difference, no biggie.

    When you retest, start with #3 first. Sometimes and depending on battery health, the last cylinder tested can show lower because it may not have the "kick" as it did on first psi test.

    If still shows lower, drop a teaspoon of oil into cylinder. If that raises psi, could be rings showing age (again, this is not enough to worry).

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  14. #10
    Cannon's Avatar
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    Should not have much ring [email protected] 125 hours..my buddies P-X 255 has 400+ hours runs like a champ....if you ever head to Atlanta let me know!

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