Model KR Compression Ratio?

[HarleyCreation]

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?

[Jerry Hatfield]

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.

[c.o.]

Not to sidetrack the thread to far but I have to ask.... Jerry, which of your books did you interview Tom Sifton for?