1926 Harley-Davidson 74ci Model J OHV Racing Motorcycle
Engine no. 26J13794
1909 marked the appearance of Harley-Davidson's first v-twin, though it was not until the adoption of mechanically operated inlet valves in 1911 (replacing the 'atmospheric' type inherited from the single) that production really took off. Known by the sobriquet 'pocket valve', this 'F-head' (inlet-over-exhaust) engine - built in 61ci and 74ci capacities (1,000cc and 1,200cc respectively) - would remain in production for the next 20 years. The Harley single's transmission arrangements - direct drive by means of a leather belt - were continued at first on the twin, but the need to make better use of the engine's power characteristics, particularly for sidecar pulling, prompted the introduction of a two-speed rear hub for 1914, by which time chain drive and a proper clutch had been adopted. Later that same year a conventional, three-speed, sliding-gear transmission with 'step starter' was introduced on the top-of-the-range version of the twin which, with full electrical equipment, was listed from now on as the Model J. Periodically revised and updated, the Model J had gained a front brake, stronger fork and pumped lubrication by the time production ceased in 1929.
Abandoning its strict 'no racing' policy, the Harley-Davidson factory began competing in motorcycle sport in 1914, when the 'pocket-valve' immediately proved to be the class of the field. Harley's dominance continued after The Great War, by which time the F-head engine had been significantly revised, incorporating a four-lobe camshaft in place of the original's two-lobe item. Alongside the F-heads, which were raced by the factory, dealers and privateers, the works team ran the legendary 8-valve competition model. Built in limited numbers into the late 1920s, these overhead-valve racers produced 20bhp and were a little faster than the F-heads, though the latter often proved more reliable. After the introduction of the 'flat head' Model D in 1929, almost all Harley-Davidson racers used sidevalve engines until the Sportster-based XLR's arrival in the early 1960s.
Purchased from a private seller at the Beaulieu Autojumble in 2008, this particular Model J has the 74ci (1,200cc) engine first introduced for 1921. The origin of the overhead-valve conversion is not known, nor is it known when the engine was converted, or by whom. Competitor number plates bearing the words 'Racedepartment Germany' would seem to indicate recent use in that country.