FN Four

Unveiled in 1905, the fabulous FN Four was one of the first genuinely efficient four-cylinder motorcycles on the market, sporting a shaft drive and a dedicated motorcycle frame. The original 362 cc engine was increased to the near-500 cc capacity of this 1911 model before a final 748 cc version emerged in 1914. By this stage, FN had shown that four-cylinder bikes could be just as practical and smooth-riding as singles and twins.

THE SOUTH BELGIUM-BASED FN (Fabrique Nationale d’Armes de Guerre) was an early pioneer of single-cylinder motorcycles at the start of the 20th century. By 1905 the manufacturer was breaking new ground with the development of its first four-cylinder bike. The company hired Paul Kelecom, an acclaimed engineer who had been producing highly regarded engines under his own name, as well as for other manufacturers. Kelecom used his technical know-how to construct an innovative four-cylinder motorcycle for FN, a bike that would set the standard for other early machines with the same engine configuration. The model was progressive in other ways too, with an integrated frame, magneto ignition, and lubrication system. As the Four developed, there were further refinements: rear drum brakes from 1909; an optional two-speed gearbox from 1911; and a kick-starter from 1913. The following year saw the debut of the 700, which was produced until the early 1920s, and was the last of this classic motorcycle’s line.

SPECIFICATIONS

 

Model	FN Four (1911)
Assembly	Herstal, Belgium
Production	1904-1923
Construction	Cradle frame
Engine	498 cc, in-line four
Power output	5 bhp
Transmission	Single-speed
Brakes	Drum with contracting band, rear
Suspension	Bottom-link front forks, rigid rear
Maximum speed	approx. 45 mph (72 km/h)

Rifles to bikes

As its full name suggests, Fabrique Nationale d’Armes de Guerre (FN) originally manufactured munitions. By 1900 the company had diversified into motorcycle production, and the resulting logo—combining a rifle with cycle pedals—reflected both areas of expertise.

Transmission developments

This 1911 model offered just a single speed through its drive shaft. FN later introduced two-speed transmission as standard on its Four model in 1913. When the 700 variant was presented in 1914, a three-speed gearbox was one of its many new features.

THE BIKE

Style and substance went hand-in-hand on the FN Four. As well as looking good, the leading link front forks helped provide a smooth riding experience, while the brass tank under the cross tube was split into fuel and oil sections. Useful features included viewing windows inside the crankcase—which made it possible to check the oil level—and auxiliary lubrication provided by a manual pump on the oil tank.

FN badge with rifle and pedals

Carburettor air lever on handlebar

Oil metering device

Fuel gauge

Enclosed fork springs

Leather saddle

Fuel tap

Pivoting-link forks

Final drive casing

Hand-operated oil pump

Chain for pedalling

Back sprocket and rear brake

ENGINE

The FN’s four-cylinder engine was enlarged a number of times over its lifetime. The engine was redesigned for 1910 and remained unchanged for the 1911 model shown. The engine size increased to 498 cc, the carburettor position was moved, and a new oiling system introduced. The final 750 cc version of the Four replaced automatic inlet valves with a mechanically operated side-valve configuration. This produced a model with sufficient power to be employed as a sidecar motorcycle, and was also used by German forces in World War I.

Left-side view of engine

Exhaust header pipes

Spark plug

Single carburettor and float chamber with priming plunger

Ignition distributor

Oil levels

 

It is a quote. The Motorbike Book – The Definitive Visual History 2012