04 Sep Two Wheelin’: FN Four

Following on from former FMM Curator Wayne Harley’s regular On Yer Bike feature, workshop technician JP du Plessis takes to the handlebars in a new monthly series about bikes. He starts off taking a shot at a pioneering motorcycle… 

The Franschhoek Motor Museum has some wonderful unrestored and exceptional historic gems in its motorcycle collection, one of which is the remarkable circa 1905 FN Four, the world’s first production inline-4 motorcycle. FN (La Fabrique Nationale d’Armes de Guerre), a Belgian company, was initially founded as a munitions manufacturer, hence the rifles on its logo. Anyone who served in the South African army might recognise the name FN from the FAL rifle, from which the R1 rifle was closely reproduced for the SANDF.

FMM’s FN Four is in ‘barn-find’ original condition, and although not a runner it has been well-kept for display purposes. The early FN Four motorcycles featured a vertical, 362cc inline-4 that put out 3,5-3,75 hp (+-2,5 kW) at 1 800 r/min. The engine was built with reliability in mind, and thus the crankshaft was drop-forged in high grade steel and the exhaust valves were made of chrome steel to reduce pitting of the surfaces. An automatic, float-fed carburettor supplies a uniform fuel mixture to the inlet-over-exhaust configuration manifold. Ignition sparks the engine into life by means of a Bosch magneto, mounted low and in line with the crank case to maintain the centre of gravity in one plane. The little hand pump is conveniently placed on the side of the fuel tank and is used to maintain the pressure for the oiling system while riding.

The transmission was somewhat of a novelty for its time, making use of an enclosed bevel gear-and-shaft-drive delivering power to the rear wheel via six helical springs located inside the flywheel assembly to absorb the forces of combustion. The front brake is lever operated from the handlebar, while the rear brakes were operated by back-pedalling the free-pedal device, which also aided the starting procedure. When starting, decompression levers on the handlebar are depressed to get the pedals in the desired position to crank over the engine.

As they say with cars, the first race was when the second car was built! Same goes for motorcycles, I guess…  At the 10-lap 1908 Isle of Man TT, a FN motorcycle was also the first four-cylinder motorcycle to compete in the event. Rider Ronald Clark finished in third place in the ‘Twin-Cylinder’ classification with a time of 4:11:02,8 averaging 37,79 mph (60,8 km/h ) and received a prize of £10 for his effort!

The FN Four is curently on view in Hall B.