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Model KR Compression Ratio?

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  • Model KR Compression Ratio?

    I know that the basic Model K road bike had a compression ratio of 6.5 to 1.

    But what was the compression ratio of the racing Model KR? Was it higher than the standard road K model or not? In the only H-D document that I have that lists the KR compression ratio, it says "Not Available"!

    Does anyone who collects KRs have reliable information about the KR compression ratio?
    Herbert Wagner
    AMCA 4634
    =======
    The TRUE beginnings of the Harley-Davidson Motor Co.

  • #2
    Originally posted by HarleyCreation View Post
    I know that the basic Model K road bike had a compression ratio of 6.5 to 1.

    But what was the compression ratio of the racing Model KR? Was it higher than the standard road K model or not? In the only H-D document that I have that lists the KR compression ratio, it says "Not Available"!

    Does anyone who collects KRs have reliable information about the KR compression ratio?
    This applies to 1952-1954 KRs, when Tom Sifton was "King." After that the factory racing department accepted a borrowed Sifton engine and duplicated the porting, and I never got as deep into the post-Sifton KR era.

    When I interviewed tuner/builder Tom Sifton, whose KRs were faster than the Milwaukee-prepared 1952-1954 KRs, Sifton said every one of his porting improvements increased torque or horsepower or both, but each improvement had the coincidental impact of lowering the compression ratio.
    Jerry Hatfield

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    • #3
      Not to sidetrack the thread to far but I have to ask.... Jerry, which of your books did you interview Tom Sifton for?
      Cory Othen
      Membership#10953

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