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'81 GS650GL Compression Test Values

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    #1

    '81 GS650GL Compression Test Values

    I bought this bike this spring and it runs reasonably well. It idles a little rough when first started but I know the carbs haven't been looked at in quite a few years.

    I just did a compression test out of curiosity sake. The dry values were 120-125 psi across all four cylinders. A little lower than what the book says (should be 150 psi+).
    When I added oil to each cylinder the values jumped to 160-180 psi.

    Firstly, are the dry values reasonable for a bike with 57,000 km?
    Secondly, if the wet values are a sign of trouble, what would likely be involved? ie. just rings, or rings and honing, pistons, etc?

    Thanks for any replies.
    Tags: None
    #2
    Sounds like honing and pistons only, but won't know for sure till you inspect and measure the pistons & cylenders. No matter how they look, with 57,000 mi should have valve job & seals. Good luck

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      #3
      Any other thoughts?

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        #4
        Has the bike been frequently used, before you bought it?
        Piston rings might just be a little sticky. In that case, spray a little WD40 in the cylinders, let it sit for a night, and try again.
        Bad carb sync might be the reason for the idling problem.

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          #5
          The previous owner said the bike basically sat for the three years he had it. Before that I don't know. I've put about 200 km on it since I got it and I just did the test. Maybe if I ride it more the rings will loosen up?

          You're probably right on about the carb sync. When the "motorcycle fund" builds up again I'll take the bike in and get the valve clearances checked and get the carbs cleaned and sync'd.
          I'd like to tackle this myself, but for $200 or less I'd rather let someone else do it with some experience.

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            #6
            It might get better the more you use it.
            And you're right, if you want to get the job done right, let a specialist do the work....

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              #7
              sorry to say every "specialist" I've taken my vehicles too, HAVE GIVEN IT BACK WITH MORE PROBLEMS THAN I GAVE IT IN.
              and usually screwed up what i brought it in for..

              bikes are relitively EASY to work on if you have ANY mechanical ability (can you change a light bulb).. HEE HEE

              Get a good book and learn to do it yourself. NOBODY cares about your bike like you do and you know the job is done right.

              Stimpy

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