This is a curious straddling of technologies by Harley-Davidson, especially when you consider the Flathead was discontinued one year after the Knucklehead, the younger engine, was discontinued.

While you may be able to name a dozen prominent American manufacturers, few produce a product as legendary and iconic as Harley-Davidson ... the Flathead remained Harley's mainstay engine through ...

Harley-Davidson This engine, later increased to 61 cubic inches and then 74 cubic inches, was such a strong and sturdy success, it was used all the way up through 1929, when H-D replaced it with the ...