Moto BM Motorcycles

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Moto BM Bonvicini 48 Somaschini

Engine: Single cylinder four-stroke OHV

Bore & stroke: 38 x 40 mm

Engine Capacity: 47.75cc

Compression ratio: 7.8:1

Maximum power: 1.9 h.p. @ 6,200 rpm

Valves per cylinder: 2

Carburettor: Dell'Orto

Cooling system: Air cooled

Lubrication: Wet sump forced circulation with mechanical gear pump

Transmission: Gear primary, chain final

Clutch: Cable operated with multiple wet disk

Gearbox: Manual 3-speed, gear shift

Starter: Kick-starter

Throttle: Cable operated

Frame type: Tubular and pressed steel

Front Suspension: Telescopic forks

Rear Suspension: Dual dampers and swingarm

Front Brake: Drum

Rear Brake: Drum

Front tyre: 2.00 x 2.4 in.

Rear tyre: 2.00 x 2.4 in.

Seat: Dual seat

Fuel consumption: 1 litre per 70 km

Top speed: 60 km/h

Towards the end of 1954, BM presented a simple and inexpensive 48cc engine, from which the following year it obtained three well-made mopeds named respectively Signora, Sport and Supersport. The four-stroke engine was built by Somaschini of Trescore Balneario, in the province of Bergamo. This company has long been active in the field of precision machining and had established an excellent reputation in the motorcycle sector for its gearbox components. It began to manufacture engines, and these were chosen for some of the Moto BM lightweights. The engine had a cast iron cylinder, pushrods and rocker arms, and forced lubrication with gear pump. The gearbox was three-speed, and it was available in versions with 1.8 to 2.4 horsepower.

The BM four-stroke mopeds remained in the catalogue for several years, but did not achieve great popularity in part due to their price, considerably higher than the two-stroke models from the same manufacturer.

Source: Hessink's NL

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