While Tom Henderson ran the company, brother Bill proved to be one of the finest engineers in the USA’s early days of motorcycle R&D, and the quality of his designs arguably outranked anything yet made by a European manufacturer – even Belgium’s FN company, which had invented the four-cylinder motorcycle in 1904. This resulted in the Henderson brothers’ products being christened two-wheeled Duesenbergs, considerably better engineered than the contemporary Pierce Four.
After building a single prototype in 1911 with belt final drive, in January 1912 Henderson Motorcycle Co. began manufacturing 25 examples for public sale of its first 7hp Model B Four powered by an F-head (inlet-over-exhaust) 934cc inline longitudinal engine with mechanically-operated valves and fully-enclosed chain final drive. While it had just a single-speed transmission, it did have a clutch-an uncommon feature on bikes of that era. Costing $325, the new Henderson Four retailed for $75 less than its Pierce rival, whose demise it surely hastened. On one of these its owner Carl Stearns Clancy became the first man to circumnavigate the globe on two wheels in 1912-13, covering 18,000 miles in 10 months of hard riding through four continents, on what was the longest and most perilous motorcycle journey yet attempted.
An immediate commercial success with 2,000 examples built and sold from 1913 onwards, the Henderson Four was continually improved by the two brothers, and significant advances were made with the 1917 Model G. The oil was now held in the crankcase, as in a car, replacing the much inferior splash system, while a three-speed gearbox replacing the previous two-speeder was attached to the rear of the engine. Strong sales of the Henderson Four yielded capital for further product R&D, but without a range of smaller capacity singles and twins to
