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4117
MOTOBÉCANE
500cc B5C Grand Sport - 1932
French four-valver
Eight years after its foundation, Motobécane felt the need to branch out in a new direction without abandoning its primary aim of producing basic two-wheeled transportation. Motobécane had chosen to diversify into the field of the big-single. Actually, it had made its first timid steps in 1927, using British-made Blackburne engines and Burman gearboxes.
A Choice of Sizes
In 1930, Motobécane adopted unit-construction with its "B" engines, which came with everything but the gear-sets. Designed for machines of 250 to 350cc, the same bottom end was used for the 175 (for which it was too heavy) and for the 500 (for which it was a bit on the light side) Then the firm offered a Grand Sport version of the 500 in 1932, with a cast-iron "pent-roof'' four-valve head.
Record of Sport Achievement
This outstanding machine quickly acquired an enviable record of achievement in events combining speed and endurance. There were class wins in the Bol d'Or in 1932 and 1933, ridden by Lovinfosse, and in the 1932 International Six Days' TriaL This four-valve sportster was warranted to do 80 mph but cost 10 percent more than the two-valver. The "B" engine only lasted four years. The clutch – which had an auxiliary pedal control – was too heavy, and the hand-shift gearbox only had three speeds. It was replaced by the "S" power unit, initially with three speeds, then with four speeds and a foot-change. There was an ultra-rare S5C Grand Sport version with the four-valve head. Sadly, at the end of 1937, came a revised "S" type "Superculasse" with only two valves.
SPECIFICATIONS
Engine: 493cc (80x98mm) air-cooled single-cylinder four-stroke; Novi magneto ignition
Valves: overhead; four valves
Fuel System: Amac carburetor
Transmission: 3-speed hand-shift, chain final drive
Suspension: girder forks (front); rigid (rear)
Brakes: 6.7 inch drum (front & rear)
Wheels: 19 inch wire (front & rear)
Weight: 320 lb
Maximum Speed: 80 mph
Main picture shows the B5C Grand Sport exhibited at the 1932 Paris Salon, with the last of the four-valve Motobécanes.