Topic: '73K vs '78F, CB750 top end mix & match

[oldbikeracing]

 I am in the process of building a 1973 CB750K for the USCRA's, Heavyweight Supervintage road racing class. I have access to a cylinder and cylinder head (bigger valves), that came from a 1978 CB750F. Does anyone know if the 1978 CB750F cylinder and head, would be a direct "bolt on" to my 1973 CB750K lower end? I am concrned with oil passage ways, etc., etc.
 Thanks, Dave Evans - Team Old Bike Racing  #590

[scondon]

 As long as you use the F2 head and cylinder together there is no concern with oil passageways. There is concern with the F2 valve angles causing premature guide wear, a lot of these motors didn't make it past 20,000 miles on the street. Use strong guide material and make sure the stock valves aren't mushroomed at the tip where the rockers hit. Also, the F2 combustion chamber is larger and domed pistons were used in order to bring the compression back up. Using K or early F pistons will result in comp ratio loss. Not sure what cam to use besides the stock F2 but Buzz at dynoman has options.

    For strength and durability it may be wiser to install larger valves in a K/early F head, especially for racing. More coin, I know