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  1. #1
    mibunkerking's Avatar
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    bad compression #'s, but good top end?

    i ran a compression test on my xpl today and got 120/55 (pto/mag). so i took the head off to see what is going on in there and all seems fine. the pistons dont have exessive clearence from the walls and the edges are not rounded off. the walls are still clean and shiny. the mag walls are perfectly smooth with no scaring at all. just a nice crosshatch. the pto is also shiny but with very slight scaring. the funny part is, thats the 120psi cylinder!

    took the raves off to get a look at the rings and sides of the pistons and all looks good. ran a flat head along the side of the piston through the rave slot to check for bumps or scaring and there is no signs of damage.

    i just did the top end on this motor with your guys help less than 10 hrs ago.

    am i missing something here? is there somthing else that could cause a loss of compression like this?


  2. #2
    96XPSS's Avatar
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    Reeds.

  3. #3
    mibunkerking's Avatar
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    just checked them and they seem to be ok. did a quick compression test with them out and got 125/60. any other ideas.

  4. #4
    96XPSS's Avatar
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    Pull the spark plugs and stick your thumb over each hole. You should be able to notice if there is a 90 lb. difference. It may be your gauge. Were the RAVES down in the same position when you had the head off?

  5. #5
    Richieb's Avatar
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    Ring broken, or gummed in the ring land.

  6. #6
    mibunkerking's Avatar
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    Quote Originally Posted by 96XPSS View Post
    Pull the spark plugs and stick your thumb over each hole. You should be able to notice if there is a 90 lb. difference. It may be your gauge. Were the RAVES down in the same position when you had the head off?
    they feel about the same. it is a brand new gauge, this is only the 3rd time i have used it.

    i didn't look at the postion of the raves when i had the head off, but i did take them out and check them. they slide smoothly and appear to be down all the way now at the least.


  7. #7
    flyin' the friendly skies airbornexp's Avatar
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    last time this happened to me I had too much oil in the crank case..just thinking out loud

  8. #8
    KrunchovXPL-GTX-RX's Avatar
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    I have called you all here tonight because someone in this room is a murd....uh, wait, wrong thread.

    Where was I? Oh yeah...

    Which did you check first, mag or pto?

    If it was the pto, did you check it again after getting that low reading on the mag?

    Now where the heck did Watson get off too now?

  9. #9
    2Blue's BFF! dsolie's Avatar
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    bad head gasket? leaking out of the raves?? Spray soapy water and crank it then!

  10. #10
    mibunkerking's Avatar
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    I checked the mag first as it was easiest to get to. I will check the crank case for excessive oil and the head and raves for leaks when I get home.

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