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    Another "What does it mean when..."

    What does it mean when I can hear compression being lost out of the crankcase and head when I turn the engine over by hand? I'll explain. I currently have the clutch out and the valve cover off. When I turn the engine over by hand I can distincly hear air hissing out of the area in the clutch space where I can now see the crank. The hiss at the head could be at the exhaust openings I suppose, or maybe just a clearance issue, but I am really concerned by the hiss in the crankcase. Does this definitely mean my rings need replacing and the jugs a hone? Also, can I do a compression test (albeit with a cold engine) without the valve cover on? I tore up the gasket removing the valve cover and won't be ready too buy a new one yet.
    Currently bikeless
    '81 GS 1100EX - "Peace, by superior fire power."
    '06 FZ1000 - "What we are dealing with here, is a COMPLETE lack of respect for the law."

    I ride, therefore I am.... constantly buying new tires.

    "Tell me what kind of an accident you are going to have, and I will tell you which helmet to wear." - Harry Hurt

    #2
    hiss

    Yes no yes no and yes yes yes, The hiss is for the most part normal, there is no 100% ring seal, you can do a comp check cold, but will read lower than hot and will very bike to bike, about 10% on an average lower, and if the bike has sat then even lower, put it back together and run it, then go from there, or if it has high mileage on it and you are half way into haveing it out I would do the top end, proved you have the funds to do so.

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      #3
      Top end being the head or the cylinders or both? It's pretty far apart right now and I've dedicated the whole winter (or as long as it takes) to restore the bike. It's got 37,700 miles on it, the head was replaced recently with a used unit- it has a total of about 12,000 miles on it. About 2 years ago I tested the compression and came up with around 110 per cyl- low, but not horrible and all within 10%.

      I just don't know how far to take it. Maybe all the way- I'm having fun doing it!
      Currently bikeless
      '81 GS 1100EX - "Peace, by superior fire power."
      '06 FZ1000 - "What we are dealing with here, is a COMPLETE lack of respect for the law."

      I ride, therefore I am.... constantly buying new tires.

      "Tell me what kind of an accident you are going to have, and I will tell you which helmet to wear." - Harry Hurt

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        #4
        compression

        Sounds like its time to do the rings, as long as you did the compression check right, hot, valves adjusted, throttle wide open, and air filter clean or removed, I have 145 on mine with about 32,000 on it. you don't really know till you open it up to see what it needs, I did my trans bearings at 30,000, if its fun then have at it

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