It was preceded by a boxer 4 manufactured in 1897 by Henry Capel Lofft Holden, and an obscure air-cooled inline-four developed in 1903 by C. The FN Four was the first production inline-four, but not the first motorcycle with a four-cylinder engine. Hodgdon, Motorcycling's Golden Age of the Fours, 1976 Lthough there were four-cylinder motorcycles prior to the FN, none came near matching the eminently successful and practical performance of the FN right from the beginning. The intake valves were atmospheric, pushed open by ambient air pressure against light springs during the piston's intake stroke, up to the 1914 748 cc model, which replaced the automatic inlet valves with mechanically actuated side valves.
The engine had to be periodically oiled during riding, with hand pump. The displacement increased over time, to 410 cc in 1906, later to 498 cc for the US market, and a 748 cc variant was produced in 1914. įN originally fitted the Four with a 350 cc or 362 cc engine. The air-cooled longitudinal layout was prone to overheating the rear cylinders, a trait overcome in later designs with water cooling and transverse layout. The FN Four's engine was designed by Paul Kelecom, who had designed single-cylinder engines prior to the FN. Four-cylinder engine Įnd section showing inlet over exhaust valves and atmospheric intake. The motorcycle had bicycle-style pedals used for starting until 1913, when a kickstarter was adopted. : 43 The US model had either Goodrich or another imported brand of tires, and a leather seat made by the Mesinger Bicycle Saddle Company of New York. Engine power was raised from 4 + 1⁄ 2 hp (3.4 kW) to 5 hp (3.7 kW), the frame size was reduced from 22 to 20 inches (560 to 510 mm) allowing the rider to sit with both feet on the ground, the wheel rims were made heavier and would fit American tire sizes, and it came with tires with a heavier tread. įor the US market, the 1908 model was upgraded and released as a 1908 1⁄ 2 model, called the F.N. In 1910 the engine was redesigned and enlarged to 498 cc (30.4 cu in), the carburetor was moved and a new oiling system was used. īy 1908, it had a two speed transmission with a plate clutch, overcoming the speed limitations of the earlier model. It had a 5:1 reduction ratio to 26-inch wheels. The 1905 model had a high-tension Bosch magneto ignition, : 43 a spray carburetor, and a rear coaster brake operated by the pedals. The rider started the engine by pedaling bicycle style pedals with a chain drive and sprockets to the rear wheels. It had a single-speed shaft drive turned by a bevel gear. In 1909, a two-speed transmission was offered, then three-speed in 1914 with the 748 cc engine. The motorcycle was originally single-speed.