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    Compression test question - GS400

    Does anyone know what the compression readings should be for a GS400?

    I did a quick test last night and it was 90 psi - couldn't find the oil can so I will do the test with a squirt of oil tonight to see if I get a higher reading.

    #2
    New, compression would be in the 145-170 range. If the engine has not been run for some time, the cylinders will be dry and the rings may be stuck a bit, so a compression check would not be accurate. I had the same situation with my 1100 when I got it. Compression was around 60 psi on all four. I sprayed a liberal amount of PB Blaster in each spark plug hole and let it sit for a couple days and rechecked the compression after turning the engine over a couple dozen times with a wrench. Compression was 140 all around. :-)

    Earl

    Originally posted by rhscanada
    Does anyone know what the compression readings should be for a GS400?

    I did a quick test last night and it was 90 psi - couldn't find the oil can so I will do the test with a squirt of oil tonight to see if I get a higher reading.
    Komorebi-The light filtering through the trees.

    I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion. H.D.T.

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      #3
      Originally posted by earlfor
      New, compression would be in the 145-170 range. If the engine has not been run for some time, the cylinders will be dry and the rings may be stuck a bit, so a compression check would not be accurate. I had the same situation with my 1100 when I got it. Compression was around 60 psi on all four. I sprayed a liberal amount of PB Blaster in each spark plug hole and let it sit for a couple days and rechecked the compression after turning the engine over a couple dozen times with a wrench. Compression was 140 all around. :-)

      Earl
      Thank you for your reply Earl,

      The bike has been sitting for 5 years before I purchased it a couple of weeks ago. You wouldn't believe the muck that was in the carbs.

      I will get some PB Blaster and try that. Thanks for the info.

      I will report back later.

      Roger.

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        #4
        Make sure you hold your throttle open when you do the test as well.

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          #5
          Compression test failed

          Well I finally got around to performing the compression test properly (throttle fully open). The results were not good. Both cylinders would not go above 100psi even with oil in the cylinders.

          I decided to take the plunge and yank the engine from the bike. I took it apart and found that there was about a 1 to 1.5mm gap between the piston and bore - the reason why I was getting low compression. The rings were not stuck. Looks as though I will have to do some reboring.

          Does anyone know where I can mail-order oversize Suzuki pistons?

          Roger

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