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Are new piston rings needed?

Discussion in 'XJ Technical Chat' started by simplegreen8, Apr 28, 2023.

  1. simplegreen8

    simplegreen8 New Member

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    (Keep in mind I don't know much about motorcycles)
    Im doing compression tests on a beat-up 1992 Yamaha Seca II that I assume has been sitting for a long time.

    3 of the cylinders read 145-150 PSI. 1 of them originally read 60 PSI, but with a little bit of oil squirted in the cylinder, it immediately went to 180 PSI. I tried putting oil in the other cylinders, and they also read around 180 PSI.

    Are the piston rings bad on that cylinder, or could it be they were just stuck from sitting? I tried a compression test a few hours later and got 180 psi again. Will the oil eventually drain in order to test again dry?

    Overall, is it worth it to tear it down, or should I move on and get the carbs cleaned up and try to start?

    Thank you,
    The attached image is how I bought it.
     

    Attached Files:

    simplegreen8, Apr 28, 2023
    #1
  2. Franz

    Franz Well-Known Member

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    Don't tear it down. Rings stuck from sitting on 60 psi cylinder. Put a small amount of automatic transmission fluid/acetone 50/50 mix in through the spark plug hole and let it soak to free the rings.
     
    Franz, Apr 28, 2023
    #2
    Andrew Nichols and Jetfixer like this.
  3. Jetfixer

    Jetfixer Well-Known Member

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    Agree with Franz , run it like you stole it , and then do a compression test .
     
    Jetfixer, Apr 28, 2023
    #3
  4. jayrodoh

    jayrodoh YimYam

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    Me three, run it and I'll almost guarantee you the numbers will increase. Easier to try that vs. a teardown anyway.
     
    jayrodoh, May 3, 2023
    #4

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