1929 Harley-Davidson 1,200cc Model JDH 'Two Cam' Racing Motorcycle Engine no. 29JDH1174
* Rare 'Two Cam' model * Top-of-the-range super-sports machine * An older restoration
Following an abortive debut in 1909, the twin-cylinder Harley-Davidson returned for 1911 in redesigned form boasting mechanically operated inlet valves, replacing the 'atmospheric' type inherited from the single. Production really took off and this 'F-head' (inlet-over-exhaust) 'pocket valve' 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 up-dated, the Harley-Davidson F-head twin had gained a front brake, stronger fork and pumped lubrication by the time production ceased in 1929.
Before then, Harley-Davidson had introduced a new high-performance variant, known as the 'Two Cam', which was an addition to the range in 1928. This twin-cam arrangement had first been seen in 1916 on the works-only eight-valve racers and was adopted on the factory's F-Head racers in 1919. Thus equipped, the racing F-head twins were only slightly slower than their overhead-valve siblings but were considerably more reliable.
The roadsters' twin-cam F-head engines are easily distinguishable from their lesser cousins by distinctive peanut-shaped timing covers and side-by-side (as opposed to fore-and-aft) direct acting tappets. They were also fitted with Dow Metal magnesium alloy high-compression pistons. Other distinguishing features of these top-of-the-range models included a slimmer fuel tank, 18" diameter wheels and - most importantly considering the performance on offer - the provision of a front brake. Priced at $390, the 74ci JDH 'Two Cam' was the most expensive model in the range. For the Harley-Davidson devotee, these limited-production 'Two Cam' hotrods were the ultimate high-performance roadsters of their day and as such are among the most sought after of pre-war Harleys by today's collectors.
There are no documents with this restored Model JDH 'Two Cam' racer.