I was speaking with Erik in Alaska tonight about KR Double Valve Spring Covers, an esoteric subject, and the conversation naturally steered itself to the production bike versions. Erik mentioned something about the early production bikes having 4-flat lower covers, and the later ones having "more flats".
I looked at the bikes in our Gallery section, and one of the 1952 Ks has the 4-flat bottom covers. The rest of the 1952s and 1953s have the 6-flat covers.
I looked at the 1953 Spare Parts Catalog (date October 15, 1952, the beginning of the 1953 model year), and it shows p/n 18255-52, but the illustration shows a 6-flat lower cover. The 1954 Spare Parts Catalog shows p/n 18255-52A, and the same 6-flat illustration.
Aye, there's the rub... The above suggests that the 4-flat covers were only used during 1952, perhaps only early 1952.
Do you have any insights into when the 4-flat covers were used? Or better photos?
Enquiring minds want to know!