AJS V4

The AJS V4 (1935 – 1939) started out as a prototype air-cooled V4 road bike, but became a water-cooled and supercharged racing bike.

In 1935, at the Olympia Show, the Bert Collier designed air-cooled sohc AJS 50° V4 was first displayed. It was a fully equipped road going version, which did not make it into production. This first version used a common crankcase with four individual cast iron cylinders and separate alloy heads, with exposed hairpin valve springs, and a 180° crankshaft with forked conrods. There was a central carburettor for each pair of cylinders, and fore and aft exhausts. The single overhead camshafts were chain driven. It had chain primary drive in an oil bath primary chain-case, and a wet clutch. It was stated by AJS at the time that there would be the option of replacing the forward mounted chain driven dynamo with a supercharger. The AJS used a rigid frame with girder forks.

In the spring of 1936 a new racing version with alloy barrels appeared at Brooklands for testing, wearing a Zoller supercharger, driven at half engine speed, and fed by a single Amal TT carburettor. The ERA GP cars of the time used a larger Zoller supercharger. It made 51.5 bhp (38.4 kW) at 6000 rpm. All exhaust ports now faced forward, and a branched inlet manifold fed the engine with 8 psi of boost. The engine was now mounted in the same frame as the 500 cc OHC single TT racers, and used a four-speed Burman gearbox with a dry clutch.

In 1936 Harold Daniell and George Rowley rode the AJS supercharged V4s in the Isle of Man Senior TT, but despite its high top speed, it lacked acceleration. Both riders retired due to mechanical problems.

Considerable work must have been done at the new AMC race shop, because the next version did not appear until 1938, and when it did it had a plunger rear suspension, better brakes, revised and lighter induction manifold, and raised compression. The engine had been mounted further back in the frame to improve rear cylinder cooling. A R (Bob) Foster rode one in the 1938 Senior Isle of Man TT, but it retired, from overheating, after only two laps.

Where other companies might have cut their losses at this point, AMC did not. They commissioned Matt Wright, former New Imperial designer, to do a complete redesign.

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Wikipedia