Photo ou archives : F-M. Dumas
4616
MAGNAT-DEBON
400cc 4 hp -1913
Overhead-valve pioneer
Client-competition motorcycles were very popular in France before WWI, because they were developed from road-going models and because they brought a new powered sport form within the reach of amateur riders. In 1913, one of the most competitive options available was the Magnat-Debon 4 hp.
Turbulent Head
In 1912, the marque was first in France to catalogue a model with overhead valves. Rated at 2 hp, it had a fixed cylinder head with the exhaust on the right. Works rider Escoffier used a special engine with detachable cylinder head and exhaust on the left, an effort to create "swirl" and improve the burning of the gasoline/ air mixture in the cylinder. Experience gained with this engine led to the inclusion in the 1913 catalogue of an over-the-counter overhead-valve racer, the 4 hp. This also had the detachable cylinder head, but the exhaust was on the right.
Narrow Tank
The rest of the 4 hp was taken from the 2 hp tourer, with its long, narrow fuel tank, telescopic forks and one-piece aluminum carburetor exclusive to the marque. The works racers, appearing in races like the 1913 French GP, retained the left-hand exhaust, to give them an edge over the catalogue models. Provided he knew how to adjust the air and ignition levers atop the tank to get the last ounce out of the engine, the rider of the 4 hp bestrode a machine capable of an astounding performance with a top speed of 60 mph.
SPECIFICATIONS
Engine: 39&c (75x90mm) air-cooled singlecylinder
four-stroke; Ruthardt HT magneto
Power Rating: 8 hp @ 3800 rpm
Valves: overhead
Fuel System: Magnat-Debon carburetor
Transmission: direct belt drive
Suspension: sprung telescopic forks (front); rigid (rear)
Brakes: caliper rim brake and pulley rim brake (rear)
Wheels: 600x55 mm wire clincher (front & rear)
Weight: 143 lb
Maximum Speed: 60 mph
Among the fastest catalogue racers of its day, the Magnat-Debon 4 hp was modern in concept.