AJS Four 1939
1939 A.J.S. FOUR. Pre-war there was no ban on
superchargers in road-racing and these instruments, all too rare today, were
used with some success by several British and many Continental factories. A.J.S.,
then actively supporting road-racing with factory riders and machines, had for
some years experimented with an air-cooled Vee-four when in 1939 they revealed
to the public their latest hopes of achieving an Island victory in the Senior
T.T.—a Matt Wright-designed supercharged Vee-four with chain-driven single o.h.c,
twin magnetos, swinging-fork rear springing and water cooling.
It made its debut at Brooklands in May of that
year when Bob Foster took it on a few laps' "tour"—its very first ride on a
track. A few weeks later it appeared at the "North West 200" meeting, and in the
meantime had been equipped with a waterpump outboard of the engine sprockets. At
the fall of the flag Foster was struggling with a flooding carburetter float
Eventually he started a couple of minutes behind
the field but in eight laps he had screamed through the field—only to retire
with a blown gasket on lap 13—his riding number was 13 too.
In the T.T., Walter Rusk and Foster both had to stop several times for fuel and
water and could only finish eleventh and thirteenth. Rusk, however, did notch
one really good point for the model when, in August !939> ne recorded the first
100 m.p.h. lap of the Ulster G.P., held then on the Clady Circuit—but bad luck
dogged him and he was put out with a broken fork link. In this race he had
outpaced the blown Gilera four, and it is fair to assume that, but for the war,
this model would have been a real force to be reckoned with.
As it was, the machines made a few fleeting
appearances after the war— but the "blower ban" saw them taken off the active
list. Today, all that remains is an engine unit, on show in the Beaulieu Museum.
Engine: Vee-four 500 c.c. o.h.c; watercooled; chain-driven supercharger in front
of engine; chain drive to camshafts.
Ignition: two twin-cylinder magnetos.
Transmission: chain via four-speed gearbox.
Frame: duplex cradle with swinging-fork rear suspension controlled by
"plunger-type" spring boxes.
Forks: girder pattern with rebound springs.