Further Development of the 2-cam Engine
(1923 - 1929)

In 1923, H-D changed the design of their 2-cam race motor.  The crankcase was beefed up and with it the timing chest changed from the previous "banjo" shape to an irregular shape that has been loosely described as resembling a "kidney bean."  As with the banjo 2-cam, the 1923 design employed separate roller cam followers on which the tappets rode.  These motors are known as "indirect-action" 2-cams because of the intermediate step of the cam followers between the tappets and the cams.  The tappet blocks of the "indirect-action" 2-cam motors are cast as an integral part of the crankcase.

By the middle of 1924, H-D changed the valve-train design to "direct-action" where the tappets ride directly on the cams.  The tappet blocks on the "direct-action" motors are separate bronze or steel castings bolted to the crankcase.

As with the "banjo" 2-cams,  the 1923 through 1927 "kidney bean" style of 2-cam were not sold to the public.  They were supplied to factory riders or loaned to dealers for use by their top-flight riders.  These racing 2-cams displayed a three digit serial number preceeded by the letters:   "FH," "FHB," "FHAC," or "FHAD."

Along with the street version 2-cam introduced in 1928, H-D continued to build an "FH" race motor until production of all 2-cam motors ceased in 1929.  The "FH" motors are most easily identified by the fact that unlike the production model, they do not have a number boss on the crankcase;  the serial number is stamped directly into the side of the crankcase itself.

Copyright ©1996 Daniel K. Statnekov

Installed:  April 12, 1997
Revised:  June 28, 2003