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Thread: Model KR Compression Ratio?

  1. #1
    Join Date
    Jul 2003
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    Wisconsin
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    1,739

    Default 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?

  2. #2
    Join Date
    Jan 2006
    Posts
    207

    Default

    Quote 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

  3. #3
    Join Date
    Feb 2003
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    High in the B.C. Rockies....
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    5,285

    Default

    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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