Amac carburetor

MotoBecane Tank transfer



Due to a meeting between the gentlemen Abel Bardin and Charles Benoit in the post-war period of 1914-1918, the workshops of Motobécane were established in Pantin. Both engineers worked at the S.I.C.A.M. company were they were designing auxiliary engines for bicycles.

The very first prototype developed at "Sicam" by the ingenieurs Charles Benoît and Abel Bardin was the 100 cc prototype nr. 0 (zero). The ingineers, who started their own modest company named Motobécane at 27 March 1923, derived of this prototype their first 175 cc prototype under the name of Motobécane. The very first original prototype had been a 100cc with the cilindrical petrol tank on top of the horizontal frame tube, later on it was mounted beneath the horizontal frame tube but with a 175cc engine.

In 1921 SICAM partially moved from the boulevard Malesherbes to Pantin. The first design of the two engineers was a little car with three wheels that was soon succeeded by the Pelican, a four-wheeled car for maximum of two persons. This car burned down during a test-drive in the area of Paris. Due to lack of funds the two gentlemen had to restrict themselves to the development and building of a 175 cc motorcycle which was to be named Motobécane in 1923. The first workshop, rue Beaurepaire, was made of wood and had no production by machines. This is why the first model, model A, could not be made and sold before 1924. Success was guaranteed after the fair in 1924. A major factor to this success was the price; 1425 frs for a Motobécane with an 175 cc cylinder capacity against 1450 frs for an other motorcycle trademark with an 100cc cylinder capacity.

Just about 150,000 of these 175 cc motorcycles were built.

Description of the first 175 cc series

The first Motobécane engine looks a lot like the SICAM engine. The styles of Benoit and Bardin are easy recognizable in these engines; the same cylinder capacity of 175cc (boring 56mm, stroke 70mm). These two stroke engines allow an engine speed of maximum 1850 rpm and according to the data of that time, the power of these engines were 1 3/4 hp.

This motorcycle was designed for daily use, although the sales pamflet, drawn by Marcel Dupin, showed the ladies model with a female tennis player. The production of 1923 was privat and mostly consisted of prototypes. The actual production start took place in 1924 after the official deposit of the regulations of the firm. We often find MB1 motorcycles of 1923 for sale in markets and in small announcements, but the authentic model “A” is very rare to find.

Prototypes and Pre-series

The suspension part of the front fork is completely made of rolled plate steal (the scabbard technic) and the horizontally mounted spring is made of round steal thread. The leather sadle, trademark “Star”, is supported by two tractive powered springs. This mounting was to be found again on the Mobylette 51 in the eighties.

The stand is made of a round pipe and is clicked in fastened condition at the rear mudguard with cloth.

The complete pedalsystem is welded on the frame. In the catalog of 1924 the gear wheel of the pedal system of the MB1 is displayed as having 36 teeth. This picture is probably adopted from a catalog belonging to a manufacturer of accessoires for bicycles.

The luggage rack doesn’t exist in the first series. The small pedal system as we know it, appears in the second catalog of 1925.

1925 – 1927 – The main series

In this series, of which the esterical appearance shows similarities to the S.I.C.A.M. (the spark is a GILARDONI original), the spark is situated at the back of the non turn-off cylinder head. The decompressor is horizontally mounted. The magnet (France ou Bosch) is driven by a bicycle chain with a transmission of 12,7 and is protected by a oval sand blasted aluminium cover.nt>

The carburetor is a ZENITH model 15H with a choke valve on the intake and is assembled by a left turning nut. The difference is also noticeably in the crankcase which is made of an aluminium alloy and has on each half-crankcase a small projection placed into the cylinder part. The purpose of this is to reduce the volume during the bottom death centre.

This patent, one of the first deposited, would be used untill the last models of this serie till the war (’40-’45).

The baffled piston had a floating bronze pin of a 12 mm diameter, without circlips untill framenumber 5420. From framenumber 5421 and up, the diameter becomes 15 mm and the pin will be made of steal. The cylinder is made of cast iron with a non turn-off cylinder head. The first series are fitted with a decompression device to allow air to be brought to normal pressure, and with a spark plug which is fitted horizontally. The subsequent series have a vertically fitted spark plug.

The flywheel is on the left side and the outside is nickel-plated where the centre of the flywheel is black varnished. The ignition magnet is driven by a chain. The nickel-plated chain guard is equipped with a little plate mentioning motorcycle model and engine number. The magnet was bought at Magnéto-France (from 1925 on at Novi). It has lateral contact breakers. The motorcycle has to be started just like a bicycle. The pedals and handlebar are nickel-plated. The engine parts were contracted out to Maison Auffiére but the assembly was done in their own workshop. The varnishing of the frame was contracted out to Suassier, while the mudguards (black) and the tank (dark blue with a silver Motobécane emblem) were delivered by Motaz in Courbevoie. The frame was produced by Motobécane themselves and is well designed. It is autogenously welded.

The upper part of the front fork, from the joint axle to the spring attachment was made of mould iron (H profile). The stand was redesigned. It was made in U profile. The luggage rack was assembled by welded rings to the frame. The front brake was a rim brake. The tyres were 650x50 and profiled, the rims and belt drive pulley were varnished black and the spokes were nickel-plated. The handles were just as the simple throttle control, nickel-plated.

The decompressor was placed in front of the cylinder opposing the spark plug which was at the back of the cylinder and was sparked by a NOVI magnet. The protection cover of the NOVI magnet's chain was made of steal plate.

The carburetor was also replaced. The cover of the float chamber was marked with “Motobécane”. Sometimes this can be found in catalogues under the name “PIP”. The carburetor’s speciality lies in the way of the flow of the mixture. The mixture penetrates the carburetor’s chamber and is passed under a clock, which is situated on a conical cover. The mixture rises vertically through the conical cover and is suddenly turned 90 degrees while being sucked into the cylinder when the throttle control is turned. Since 1929, a silencer is attached to the exhaustpipe.

The carburetor doesn’t have a choke and the exhaust pipe is an ordinary nickel-plated pipe without a silencer but perforated with 24 holes of 4mm at the end. The ball head is provided with a blue-striped emblem. The tank and frame are not fitted with piping.

Evolution of the 175 cc with belt drive

1928 - The milestone>

The foundation of the name Motobécane and its regulations took place in 1923. The first introduction of the model A or MB1 occurred in 1924. Next to it another model with an open frame for ladies and clergymen, model B, was introduced in the same year. In 1925 the exhaust pipe was fitted with a silencer. Those motorcycles are recognizable by its frame number; up from 10,166 and engine number 10,139 were produced after 9-6-1925. In 1926 model A became MB1 while the motorcycle stayed unchanged. In 1927 a new model, MB2, of which the engine power had been raised to 2400 rpm was introduced. This model is fitted with a two-gearbox, kick-starter and a rear brake which is deployable by foot. The frame numbers up from 45,000 and the engine numbers up from 45,000 were made after 10-5-1927. In 1928 the MB1 was modified; the fuel tank got silver piping and the fuel cap became of aluminium. The front fork spring became nickel-plated and the number plate was mounted as well as on the front as on the back of the motorcycle. Model D1 with gearbox got electric light, the exhaust was slightly lowered, the sides of the gas tank were being painted, a toolbox was mounted on the tank and the foot pegs became model wagon.

The last 175 cc models with belt drive were built in 1929. Bit by bit the models up from 1926 evolved from belt to chain transmission.

The gearboxes that were used for the models MB en D were from ALBION, G.M. and Picard.