Sunday, March 9, 2014
AJS 7R 350 cc
Here are some images of Protar's 1/9 scale AJS 7R 350 cc Racing Motorcycle.
The AJS 7R was a 350 cc racing motorcycle built from 1948 to 1963 by Associated Motor Cycles, also known as the ‘Boy Racer’, first won victories for the factory, and then went on to win races for privateers when made generally available from 1954.
A new design by Phil Walker, the chain-driven overhead camshaft 7R had the history of the pre-war AJS ‘cammy’ singles behind it. Initially, the 7R was not as powerful as its competitors, producing 32 bhp (24 kW) at 7500 rpm. The duplex frame and Teledraulic front forks remained relatively unchanged during production, while the engine had a number of changes. The included valve angle was progressively narrowed, and the crankshaft strengthened. In 1956 the engine dimensions changed from the original long-stroke 74 x 81 mm to the ‘squarer’ 75.5 x 78 mm. The AMC gearbox replaced the older Burman unit in 1958.
In 1951 AJS development engineer Ike Hatch developed a 75.5 mm bore x 78 mm stroke, three valve head version of the 7R making 36 bhp (27 kW). It was called the AJS 7R3, and was Ike's response to the Italian multi-cylinder racers. They did well enough in their first year, not as well the second. For 1954 Jack Williams, the works team manager, developed the bike further, lowering the engine in the frame, and making some tuning changes that gave 40 bhp (30 kW) @ 7800 rpm. It immediately won the first two rounds of the World Championship and took first at the Isle of Man TT. These were factory specials, but one has survived, and a second has been reconstructed from spares.
AJS 7Rs won the 1961, 62 and 63 Junior Manx TT races and came second in 1966. The 1957 AJS 7R 350 cc, with 75.5 mm bore and 78 mm stroke, gave 38.5 bhp (28.7 kW) at 7600-7800 rpm, and weighed 285 lb (129 kg). The top speed was 180-190 km/h (115-120 mph).
AMC withdrew from the world of works, and one-off, road racing at the end of the 1954, with the death of Ike Hatch, and in the face of fierce competition from the other European bikes.
After this AJS made a production version of the standard two valve AJS 7R, for privateers and a 500 cc version, badged as a Matchless G50 was also sold. By the end of production in 1963 the two valve OHC AJS 7R engine made over 40 bhp (30 kW).