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SNAPSHOT 371: 1928 Brough Superior MAG-engined Straight-Four

The Brough Superior is rightly famous for its superb V-twin motorcycles – but far less well known were its four separate experiments with four-cylinder bikes, almost always intended to astound the public at the annual UK motor cycle shows at Olympia and then at Earls Court.

The first was shown in 1927. The Motor Cycle wrote that the Brough stand would be showing “an additional exhibit which is not to be marketed in 1928. This machine breaks entirely new ground, having its cylinders set in V formation with a four speed gear­box built as a unit with the crankcase.”

The engine was a doubled-up transverse vee-twin with separate cylinders. The engine was Brough’s own 994cc four-cylinder side-valve engine with a 60-degree included angle. It had coil ignition, a car-type clutch and gearbox with integral final sprocket (there must have been a bevel gear somewhere) driving a conventional chain drive to the rear wheel. Only one prototype was produced; it was shown at Olympia in a glass case guarded by policemen. The publicity was excellent, but it proved impossible to develop into a production bike.

The bike in our Snapshot is the second attempt by Brough to produce a viable four-cylinder machine. It was powered by a 900cc side-valve straight-four engine built by the Geneva-based motorcycle manufacturer and, in this instance, engine supplier Motosacoche, under the name MAG (Motosacoche Acacias Genève). The neat and compact engine had inlet and exhaust manifolds cast within the cylinder block, and a separate aluminium cylinder head. Transmission was through a three-speed box and bevel gears to a chain final drive. The bike was built, but a conrod broke on test and fractured the crankshaft. We do not know whether the example in our Snapshot is the original or a replica – but it is fine-looking bike, seen at the 2022 Vintage Revival at Montlhéry.

Brough made two more attempts to build a production four-cylinder bike. At the 1931 show was a new motor cycle powered by an in-line engine from an Austin Seven. Not only did it have reverse gear, but it also had shaft drive and two rear wheels, close enough together to meet the regulations that deemed them to be one wheel. Production was however limited to ten examples between 1932 and 1934.

Brough finally got things right with the Golden Dream, exhibited at the 1938 show. The engine had two horizontally opposed flat twins one above the other and geared together. Five Golden Dreams were produced during 1939 and another model was planned for exhibition at Olympia; but World War II was declared in September 1939 and the Brough works were turned over to the war effort, making components for Rolls-Royce. Brough Superior never returned to motorcycle production.

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