KH vs KHRM Motor Differences?

Racing K Models

Re: KH vs KHRM Motor Differences?

Postby wz507 » Wed Mar 11, 2020 1:21 pm

thefrenchowl wrote:I still wonder from time to time why the cam is offset from the tappet on Harleys...To start with it was probably just to get the valves in the right position in the cylinders despite the pitch of the gear train, but is there a physical need for it?

Opening side is often faster lift rate than closing so lifter is offset to that side to position the lifter over the rising lobe thereby minimizing side thrust on the lifter. If the lifter is centered over the lobe the side thrust is increased.
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Re: KH vs KHRM Motor Differences?

Postby panic » Wed Mar 11, 2020 2:18 pm

All of the 1936-1999 single cam OHV big twins have the cam CL offset from the pinion CL by 3/32".
The 4-cam offset (D, R, W, G, K, X, V, U) is 1/8". The intake and exhaust tappets of each cylinder are 1/4" farther apart than their cam's pitch distance. This determines the valve axis locations in all flathead 4-cam engines, and the pushrod separation distance at the tappet for the Sportster.
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