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Thread: compression test for KHK

  1. #1
    Join Date
    Aug 2007
    Location
    Illinois
    Posts
    256

    Default compression test for KHK

    What reading should we get when testing for compression? We got 25-30 psi for the rear cylinder and 0.0 psi for the front. I hope to use another testing gauge today to see if the problem is with the instrument and not the engine.
    George Tinkham
    Springfield, IL
    www.virmc.com

    1941 Indian 841
    1948 Indian Chief
    1956 H-D KHK
    1960 CH
    1964 BMW R69S
    1966 Honda Touring Benly (aka "150 Dream")
    1984 Moto Guzzi V65Sp

  2. #2
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    3,648

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    Gosh George,..

    Does it start and run at all?

    If so, the apparatus, or its application, has issues.

    (There's usually more than one.)

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  3. #3

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    start simple George..put your thumb on the plug hole & kick.Testing kickstart with a compression gauge is tricky.On E start you give it a few revolutions,hard to do that on kick statrt

  4. #4
    Join Date
    Aug 2007
    Location
    Illinois
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    Quote Originally Posted by T. Cotten View Post
    Gosh George,..

    Does it start and run at all?

    ....Cotten
    It ran when recently reassembled; however, it fouled the front plug quickly. Now, it does not start.
    George Tinkham
    Springfield, IL
    www.virmc.com

    1941 Indian 841
    1948 Indian Chief
    1956 H-D KHK
    1960 CH
    1964 BMW R69S
    1966 Honda Touring Benly (aka "150 Dream")
    1984 Moto Guzzi V65Sp

  5. #5

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    The usual rule of thumb is between 15 and 20 times the static compression ratio at or near sea level.
    KHK 6.8:1, probably closer to 6.5 actual, so 98 to 130 psi, ideally 5% or less diff front to rear.
    When boring: NEVER use 45 pistons.

  6. #6
    Join Date
    Aug 2007
    Location
    Illinois
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    I am sleeving back to stock and using pistons from Enfield Racing. Hopefully, this will give me good compression and oil seal - and make for stronger cylinders - and not reduce heat transfer significantly.
    George Tinkham
    Springfield, IL
    www.virmc.com

    1941 Indian 841
    1948 Indian Chief
    1956 H-D KHK
    1960 CH
    1964 BMW R69S
    1966 Honda Touring Benly (aka "150 Dream")
    1984 Moto Guzzi V65Sp

  7. #7

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    A sleeve doesn't make the cylinder stronger.
    Are they specifically K/KH replacements (22251-52/52A)?

  8. #8
    Join Date
    Oct 2011
    Posts
    347

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    You should be able to tell if the compression is adequate just by kicking.When you are lining up the pre kickposition and it just rolls past tdc you will get that bad feeling every flathead rider eventually gets.
    Tom

  9. #9
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
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    Quote Originally Posted by kitabel View Post
    A sleeve doesn't make the cylinder stronger....
    And it can never transfer heat the same, either!

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  10. #10
    Join Date
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    Location
    Illinois
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    Quote Originally Posted by kitabel View Post
    A sleeve doesn't make the cylinder stronger.
    Are they specifically K/KH replacements (22251-52/52A)?
    No. They are whatever LA Sleeve uses.

    I trust LA Sleeve to use the best materials and techniques for installing the sleeve. I know the material has to be better than what Harley used in 1956. My Chief got a set of LA Sleeves in the late '80s or early '90s and has run fine since then - at least as far as cylinder wear is concerned. Clearly, Nikasil lining would provide better wear characteristics and heat transfer. The crack in the cylinder skirt has me spooked; so, I decided to put stronger material in my engine.
    George Tinkham
    Springfield, IL
    www.virmc.com

    1941 Indian 841
    1948 Indian Chief
    1956 H-D KHK
    1960 CH
    1964 BMW R69S
    1966 Honda Touring Benly (aka "150 Dream")
    1984 Moto Guzzi V65Sp

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