Lot number


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Frame no.: *1100*

Engine no.: *10330*

After the war Bologna and Milan, quickly became one of the epicenters of motorcycling not only nationally but also worldwide. The companies operating in this sector were numerous, and possess excellent technology. Among those of smaller size, but not less vital than the others, there was BM Bonvicini. BM was the abbreviation of the initials of the founder and owner Bonvicini Marino, a successful motorcycle racer before WWII. (BM Bonvicini & Moto BM appear to be the same marque)

The activity began with the production of a small number of motor-powered light engines equipped with engines built by other companies, like the German JLO with its excellent two-stroke. The production included 50cc and 175cc racing machines with frames by Verlicchi. In 1952 – 53, the house had also listed a couple of models powered by the excellent NSU single cylinders of 98 and 125cc.

Towards the end of 1954, BM presented a simple and inexpensive 48cc twin 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 gearing and for the validity of its products, it had been able to create an excellent reputation also in the motorcycle sector, quickly assuming considerable dimensions and also starting to manufacture loose engines. What powered the BM mopeds was the single cylinder called Ultra, with cast iron cylinder, distribution with rods and rocker arms and forced lubrication with gear pump. The gearbox was three-speed. Versions of 1.8 to 2.4 horsepower have been produced for this engine. The latter have been equipped with an aluminum alloy cylinder with a cast iron barrel.

The BM four-stroke mopeds have remained on the list for a few years, but have not had a considerable diffusion, also due to their price, considerably higher than the two-stroke models of the same manufacturer, which have instead had a moderate commercial success, despite the modest size of the company and the sales network that is far from extensive and widespread. BM continued its activity with good results throughout the sixties and seventies, producing appreciated fifties with two-stroke Minarelli and Franco Morini engines. Later this house went into crisis and reduced its presence in the motorcycle sector until it disappeared from the scene in the late eighties. Somaschini has long since ceased the manufacture of loose motors, to concentrate on the production of high quality gear, a sector in which it continues to be an important industrial reality.

All the lots in this sale will be sold ‘as is/where is’ and Bidders must satisfy themselves as to the provenance, condition, age, completeness and originality prior to bidding.

Engine: Single cylinder OHV 4-stroke

Starter: Kick-starter

Bore & stroke: 38 x 40 mm

Compression ratio: 1 : 7.8

Engine mounting: 1,528 inches (38.8 mm)

Engine Capacity: 47.75cc

Maximum power: 1.9 bhp [HP] @ 6,200 rpm

Valve: OHV (Overhead Valves)

Valves per cylinder: 2

Carburettor: Dell O’rto

Cooling system: Air cooled

Sparks per cylinder: 1

Lubrication: Wet sump forced circulation with mechanical gear pump

Transmission: Gear primary, chain final

Clutch: Cable operated with multiple wet disk in oil bath

Gearbox: Manual 3-speed, gear shift

Throttle: Cable operated

Frame type: Tubular and pressed steel

Front Suspension: Telescopic shocks

Rear Suspension: Two shock, Swingarm

Front Brake: Drum

Rear Brake: Drum

Front tire: 2.00 x 2.4”

Rear tire: 2.00 x 2.4”

Seat: Dual

Fuel consumption: 1 liter per 70 km

Top speed: 60 km/h (37.28 mph)

For more information

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