There were two versions of the A7, the original 495 cc
(30.2 cu in) version, and an improved 497 cc (30.3 cu in) version launched
in 1950. Although its name was changed to the Star Twin and later the
Shooting Star the BSA A7 continued in production with minor modifications
until 1961.
Designed by Val Page, Herbert Parker and David Munro, the BSA A7 was the
first of the BSA twin-cylinder motorcycles and was ready for launch in 1939,
but the outbreak of World War II delayed the launch until September 1946
when hostilities ended. The very first A7 off the production line was flown
to Paris for the first motorcycle show after the end of the war. There was
huge demand for affordable transport after the war and the simplicity of the
A7 twin was helped along by the slogan 'It's time YOU had a BSA!'.
The 495 cc (30.2 cu in) twin cylinder engine produced 26 bhp (19 kW) and was
capable of 85 mph (137 km/h).[1] A single camshaft behind the cylinders
operated the valves via long pushrods passing through a tunnel in the cast
iron block. This system needed a considerable number of studs and nuts to
fasten down the cylinder head and rockerboxes, many of them deeply recessed
and requiring well-made box spanners or the then uncommon sockets. As with
other British motorcycles of the period, this kind of set-up regularly led
to oil leaks.
Most motorcycles of this period tensioned the primary chain by drawing or
rotating the gearbox backwards on a hinge with threaded rods, this was known
as pre-unit construction. The first A7 had a fixed gearbox, bolted to the
back of the crankcase, and an internal tensioner for the duplex primary
chain. This gave it the appearance of unit construction and pioneered the
system later used in unit-construction engines such as the BSA C12/C15, BSA
B40, Triumph 3TA and so on. However, in 1954 a re-design reverted to the
older system. The electrics (as was universal for larger British motorcycles
of the period) consisted of two independent systems, the very reliable and
self-contained Lucas magneto, with a dynamo generator to charge the battery
and provide lights. Carburation was a single Amal remote float Type 6 until
1955 when it was upgraded to a 376 Monobloc.
In 1954 the Star Twin was redesignated the Shooting Star
with a new swinging arm frame and the engine further developed by reducing
the stroke to 72.6 mm and increasing the bore to 66 mm, giving a slight
increase in capacity to 497 cc. By the end of production in 1961 the BSA
Shooting Star was the culmination of the development of the BSA A7, with a
deep bottle green colour scheme with light green tank, mudguards and side
panels, it had an alloy cylinder head, a duplex cradle frame with swinging
arm rear suspension, full-width light alloy hubs and 8-inch drum brakes.
Engine compression was upgraded from 6.6:1 to 7:1 and power was up to 30 bhp
(22 kW) at 5800 rpm, with a top speed of just under 90 mph (140 km/h).
Any corrections or more information on these motorcycles will be kindly appreciated.