1905 FN Four: World’s First Production Inline-4 Motorcycle

Sathurshan

April 28, 2020

This week, we go all the way back to the early 1900s with the World’s first production inline-4 motorcycle, the FN Four. Manufactured by Fabrique Nationale from 1905 until 1923.

1905 FN Four

Ever wondered how inline-four motorcycles came to life? well, it all started way back in the late 1890s. However, the first production inline-four motorcycle was manufactured in the earlier 1900s.

1905 FN four is the world’s first production inline-4 motorcycle manufactured by Belgian Firearm manufacturer, FN (Fabrique Nationale) in Liége, Belgium. Note, there have been numerous motorcycles before the FN Four was developed but they mostly used a single cylinder or horizontally opposed “boxer” twin/four engine.

The FN Four was developed in 1904 and launched later in 1905 at the Paris Motorcycle Show. Later with time, Fabrique Nationale designed and developed various different upgraded models of the FN Four which we will look into detail later. The production only ran for 20 years, from 1905-1923, however, the FN motorcycles were a massive commercial success. Want to know why? The mass production of cars for the public actually started later in 1908 which made motorcycles the prime mean of motorized personal transportation.

Did you know, the FN motorcycles also held the world record for the World’s fastest production motorcycle from 1911-1912.

1905 FN Four

Photo Credit: Newatlas

Engine 

The FN Four engine was developed by Paul Kelecom, who had also developed single-cylinder engines before the FN came to life. The 1905 FN four featured a 362cc inline-four engine. The air-cooled longitudinally mounted engine on the earlier FN Four was prone to overheating the rear cylinders. The issue was fixed in the later models with a water-cooled transversally mounted engine.

The earlier models also featured bicycle-style pedals with chain drive and sprockets to the rear wheels to start the motorcycle. This was replaced by a Kickstarter in the later models.

Back in those days, the engine had to be periodically oiled during riding, with a hand pump! Also, did you know, the intake valves were atmospheric? Meaning, the valves used atmospheric pressure during the intake strokes to operate. Impressive for the time, the bike featured high-tension Bosch magneto ignition! The 362 inline-four engine coupled with a single-speed transmission and shaft final drive produced around 3.45hp at 1800rpm which was a big deal that time.

Chassis and Brakes

Photo Credit: Newatlas

The 1905 FN Four’s frame was essentially a bicycle frame with bicycle seats. Thanks to FN Four’s simple steel bicycle-like duplex cradle frame, the bike weighed only 75kg. As for the suspension, the bike featured a single bottom-link fork at the front and no suspension components at the back. To suit the chassis, the 1905 FN Four featured 26-inch wheels. As for the brakes, the 1905 FN Four featured coaster brakes at the rear operated by the pedals.

Variants 

Fabrique Nationale made improvements to the 1905 FN Four and badged them differently over time. There were numerous improvement and changes made to FN motorcycles during the 20-year+ production run.

Frame Numbers by Year: (Not all numbers were used.)

1906

In 1906, the displacement was increased from 362cc to 410cc. Through this, the engine output jumped from 3.45hp to 4.5hp. However, the 1906 model featured the same single-speed transmission with pedal start and coaster brakes as the 1905 mode. Aside from the change in displacement, everything else remained similar to the 1905 model.

1908

In 1908, FN decided to overcome the speed limitation issues with previous models by using a 2-speed transmission using plate clutch. For the US market, the 1908 model was released as the “FN Big Four” as the engine power jumped from 4.5hp to 5hp. On top of this, the frame size was reduced for user comfort and the rims were upgraded to fit American tire sizes.

1909

In 1909, the bike didn’t receive any major updates. Everything remained similar to the 1908 model except for the upgraded drum brakes.

1910

The 1910 model was essentially a 1909 model with a bigger 498cc engine capable of producing 6hp. This engine received upgraded oiling system and carburetor.

1911

1911 model had a wheelbase of 56 inches. On top of this, there was an option to choose between  Goodrich or another imported brand of tires. Aside from this, the 1911 model featured bicycle seats manufactured by Mesinger Bicycle Saddle Company of New York.

1913

The 1913 model replaced the bicycle-style pedal starter with kickstarters. Everything else remained the same as the 1911 refreshed model.

1914-1923

In 1914, the displacement was further increased to 748cc (7 hp). With the new engine, FN replaced the automatic valves with mechanically actuated valves. On top of this, a 3-speed transmission was introduced. As a result, this bike weighed 128kg. From 1914 until 1923 the FN inline-four motorcycles essentially remained similar.

The 1905 FN Four aka Type A went on sale for 42 pounds back in 1905 (Roughly 5100 pounds in today’s money). However, a decent example would cost you around 150,000 -250,000 USD in 2020!

Though it’s been over 115 years since the first production inline-four engine was introduced, the FN Four has been instrumental to numerous other manufacturers who excelled in designing and developing multicylinder motorcycle engines throughout history.

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