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  1. #1
    Beerme's Avatar
    Join Date
    Nov 2007
    Hurricane Ally aka Polk county, Auburndale Florida.

    01 GPR 800 Question - Lost compression on Back cylinder

    Hi fellas & ladies,

    I have a buddy who lost compression this morning on his back cylinder, 30 psi while front is around 100 or so. No idea number hours on the motor as it was replaced prior to him buying the ski.

    So my question, does this sound like a head gasket or some larger problem and is it possible to diagnose prior to tearing engine apart? Engine turns over and will start but sounds rough while running, also both plugs are black....Was mixing oil at 50-1 then recently changed 32-1...

    Thanks in advance,
    Happy riding...

  2. #2

    Join Date
    Jan 2006
    Texas City, Texas
    Sears sells a "BEND-A-LIGHT which is a small powerful light that you can drop into the spark plug holes to take a peek at the cylinders and exhaust ports for possible damage. You can't use this technique to check for a broken valve or perhaps a broken reed which may also cause your symptoms.

    The standard thing to do is to pull the head and inspect for any obvious damage.

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