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  1. #1
    Ale's Avatar
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    Question SHO ENGINE - compression pressure value 120psi

    Hi everyone...
    after rebuild my engine
    I misured cilinder pressure value
    ...
    I misured 120 psi
    is this value correct?
    reference data... on yamaha manual is 86.8 psi.

    is it possible I have so higher compression in my engine?
    or is the intruments not much accurate...

    I'm sure I bought standar compression ratio pistons 8,6/1.


    thanks


  2. #2
    Orange FZS's Avatar
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    Compression varies slightly from different gauges. 120 -135 is generally where there at.

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  4. #3
    Ale's Avatar
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    ok.
    really I measure 125 but I can recheck with a better battery...
    but...
    why yamaha says... 86.8 psi?

  5. #4
    Ale's Avatar
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    Click image for larger version. 

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  6. #5
    ken02766's Avatar
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    For 10:1 compression ratio would give a 147 psi, yours is 8.6:1, ended up with 125 psi is about right.

  7. #6
    AWA MEMBER
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    Maybe that is the lowest the compression can be

  8. #7
    Gus13letter's Avatar
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    Agreed with everyone. About 125 - 135 is about normal. It is odd what the service manual says. Maybe it is a formula? I am not a mechanic, so I dont know.
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  9. #8
    Ale's Avatar
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    ok.
    my compression is ok.
    maybe like joey said... 86.8 psi could be minimun value for this engine

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