This entry is also available in: Russian Chinese (Traditional)

Motorworld’s newspaper №57

By the early 1930s, well-informed optimists realized that World War I wasn’t over and will return. So, the major Powers has started to prepare themselves for another round, which will be called later World War II.

Belgium authorities understood that hiding out in neutrality is not an option. But also they weren’t going to be a sacrificial lamb. The more so, because the Belgian forces fought heroically during the WWI, and who knows what the outcome of the Battle of the Marne would be if the siege of Antwerp didn’t draw some German forces?

The best strategists had prepared for an agile action, a mechanized war. One of them was Henri Denis, a Belgian Defense Secretary, an Lieutenant General. He launched several projects on re-equipment & mechanization of the Army and invited tenders for the creation of a heavy military motorcycle. It had to be a machine, which could be used for fire support operations, supply support as well as a communications vehicle. The requirements were as follows: It must carry three fully equipped soldiers and a machine gun. Responding to these requirements, the Belgian company FN, at the beginning of 1937, introduced a heavy motorcycle FN M12.

FN M86

By that time, FN was the major motorcycle supplier for the Belgian Army; at this, the M86 model was widely used in armies of other countries. The machine had a 600 cc one-cylinder engine.

FN M12a SM engine

For the tender purposes, FN designed an engine with more capacity: double-cylinder flathead opposed-piston engine having a displacement of 992 cc. It wasn’t the most powerful engine even in the second half of the 1990s – the engine developed 22 hp at 4,000 rpm but had a compression ratio of 5.0, which gave it the ability to run on petrol of any quality. Much attention was paid to the dirt-guard system: Amal carburetor and main electric components were under a cover, an air filter inlet was located relatively high so the machine could go through the shallow of the river (up to 0.5 m of depth). Two exhaust pipes came into the single silencer located between the motorcycle and a sidecar. The exhaust pipe going out of the left cylinder formed an arc thus preventing the pipe from a collision with a stub, boulder, etc. that was typical for opposed-piston BMW machines. A double-cradle with heavy-duty bottom pipes provided good protection for the powertrain from the bottom. On the sides, the powertrain was protected by big crash guards.

Sidecar wheel drive of the FN M12a SM

Despite of good towing performance, Belgian engineers equipped the machine with an auxiliary transmission as an addition to the hand shifted four-speed gearbox with reverse gear. But the real innovation was a sidecar wheel drive. Drive for the sidecar wheel was independently suggested by two different inventors: Peter Mozharov (Russia) and Henry Baughan (England). At the end of 1929, Peter Mozharov built an experimental Izh-2, and Henry Baughan built a trial bike with a sidecar wheel drive (Baughan’s bikes had been manufacturing from 1930 till 1936 under the Baughan marque). The Belgians were the first to use this idea for a mass-produced military motorcycle. Sidecar wheel drive was implemented via a drive shaft, which got connected when necessary (in severe road conditions). Thus the bike didn’t require compensating gear.

FN M12a SM sidecar

The double-cradle was made of heavy-duty steel pipes (the same pipes were used for a sidecar frame). A sidecar was attached to the frame via quarter-elliptic springs (other Belgian motorcycles had the same design according to the military requirements). The front suspension was a parallelogram suspension with the central spring; the rear suspension was a rigid one. All three wheels could be interchanged and hubs were mounted in such way that brakes and bearings were still in place when a wheel was removed. All wheels including the sidecar wheel had drum brakes and tires having big cleats. A spare wheel was attached to the back of the sidecar.

In January 1937, a civil model FN M12 Grand Tourisme was introduced at the Motor Show in Brussels. However, it didn’t go into mass production. In the spring of 1937, a military version FN M12a SM was prepared for military tests. Machines covered 6,000 kms (off-road, sandy, and rocky roads) for six days. Military inspectors who were scrupulously taking the records accepted the machine with an excellent mark. The military launch order consisted of 750 units. The total number produced was 1180 machines 1090 of which were enrolled at the Belgian Army. Motorcycle units of the 1st Cavalry Division got these bikes first.

In July 1938, the FN M12a SM was introduced at the International Competition of the military motorcycles in Spa. After, sales abroad have started: Iran bought 51 units and Greece bought 33 units. Several bikes went to Germany where they had been carefully examined. When Zündapp had been designing the KS750, it has used some technical solutions borrowed from FN bikes.

Zündapp KS 750 from the «Motorworld by V.Sheynov» collection

FN Tricar Т3 from the «Motorworld by V.Sheynov» collection


The powertrain and some other units of the FN M12a SM were also used in the FN Tricar Т3 (a military trike) and in a light three-wheel van (after the war).

Unfortunately, history didn’t repeat itself this time and Belgium failed at another valiant campaign. The Germans had crossed the Belgium board on 10 May 1940. On May 28th, 1940, Belgium had struck the flag. Almost every FN M12a SM was captured as war booty. A considerable number of these machines were used in the Eastern Front (including the Battle of Stalingrad). If you search for information on the Internet, you’ll find dozens of photos depicting happy German soldiers riding Belgian bikes.

Manufacturer Fabrique Nationale d’Armes de Guerre Herstal (Fabrique Nationale SA, Herstal)
Years of manufacture 1937 – 1939
Quantity produced, units 1 180
Price N/A
Today’s value N/A
Тип Flat-twin, 4-stroke
Engine capacity, cc 992
Bore and stroke, mm 90 x 78
Engine rating 22 hp at 4000 rpm
Sparking Battery type
Carburetor Amal 28 mm
Battery 6 V
Clutch Single-plate, dry
Transmission 4-speed, with ф reverse gear and a reducer
Frame type Duplex steel tubular
Front suspension Parallelogram with a friction damper
Rear suspension Rigid
Brakes Drum type
Wheel size 4,00 х 19
Length, mm
2 385*
Width, mm
1 650*
Height, mm
1 010*
Wheelbase, mm
1 510
Ground clearance, mm
Seat height, mm
Mass, kg
Gas tank size, l
Maximum speed, km/h
Range, km

* – Data on the results of the measurement at the exhibit of “Motorworld by V.Sheyanov”.