Like several other early motorcycle manufacturers, La Fabrique Nationale d’Armes de Guerre (FN) began as an armaments manufacturer but expanded to the production of motorcycles in 1900.

The company’s first four-cylinder model was produced in 1904 and first exhibited at the 1905 Paris Cycle Show. The 363cc air-cooled engine featured ‘atmospheric’ inlet and mechanical exhaust valves, a five-bearing crankshaft, individual crankcase oil wells and a Bosch magneto ignition system. The four-cylinder unit was far smoother than its single- and twin-cylinder rivals and final drive was via an innovative driveshaft housed inside the right-hand frame member. The engine was enlarged to 410cc in 1906 and 498cc in 1910, and a two-speed gearbox was fitted within the driveshaft housing in 1911.

The motor was almost continuously revised and redesigned, with the earliest Type A versions having no cooling fins on the cylinder heads and a variety of lubrication systems. The 410cc Type B motor (1905/06) had a straight inlet manifold with a rotating-barrel throttle and a new carburettor design. The Type C featured a rear crankshaft oil-retaining ring and a reduction in the number of plungers in the flywheel spring drive from three to two. The Type D (1907) motor featured inspection windows in the crankcases and the oil pump was located on the right side of the oil tank. The Type E (1907) engine featured bronze bush bearings in the connecting rods.

On the Type F (1908) model, the side plates of the front forks were modified to allow for a shorter steering head. In 1909, the throttle lever was moved from the tank to the handlebar and the valve lifter had its own lever rather than being operated from the rim-brake lever and the brake system was modified to include a band brake on the outside of the brake drum. Longer guards were fitted front and rear and footrests were available as an option.

In 1910, the redesigned 498cc motor featured more cooling fins on the cylinders, the spark plugs were moved from the top of the cylinders to the right side between the valves and the inlet manifold was revised to locate the new carburettor at the left of the engine between cylinders two and three. The lubrication system included a drip feed to compliment the hand pump with oil fed to four locations on the underside of the crankcases via elaborate external plumbing.

The 1912 model featured longer handle bars, and improved seat, a tubular rear carrier and a new stand, and a Bosch ZFN4 upright magneto with internal distributor was adopted in place of the earlier inverted magneto and external distributor. Optional extras included a clutch and valances on the front mudguard.