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  1. #1

    GP800R Compression

    I just checked my compression. 155 front cylinder 130 rear cylinder. Is that okay? It is a 2003 with 67 hours on it. completly stock

  2. #2
    Your gauge is off. Stock is 120 on each cylinder. Make sure when you do the check you have the throttle wide open.

  3. #3

    Join Date
    Aug 2011
    West Palm Beach FL
    If it Helps i have a 2001 and the comp. is 118 on both

  4. #4

    GP800R compression

    I checked it with a different gauge and it come up with 160 front and 140 back. Is this not possible?

  5. #5
    jlfx car audio's Avatar
    Join Date
    Jul 2011
    jackson, TN
    Not with stock head its not

  6. #6
    mudslanger's Avatar
    Join Date
    Jul 2010
    Huntsville Al
    It sounds like someone has done some work on it. or the gauges are faulty but they both seem to be close to the same difference between the 2 cylinders and that is a lot 20psi of difference. one cylinder is working harder than the other and it would be better if it was only 3 to 5 psi difference.

  7. #7
    Happily Self-Employed WFO's Avatar
    Join Date
    Nov 2005
    Houston, Texas
    I had an 800 with higher than normal compression and it ended up being the powervalve pin rattled out and the valve dropped (and was rubbing on the piston) causing the compression to be higher on just that cylinder

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