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Sunbeam S8
Designed as Britain's answer to the BMW, the
Sunbeam S7 and later the S8 were odd mixtures of the inspired and the
impractical, which was ultimately to condemn them to being an interesting'
backwater, rather than part of the mainstream of post-war motorcycling.
Several influences were at work, but the new
machines were BSAs in all but name. Sunbeam had ceased to be a truly separate
entity during the 1930s, and the trademarks now belonged to the giant BSA
organisation, which reasoned that they could capitalise on Sunbeam's
'gentleman's motorcycle' image for their new tourer.
The design was the work of independent designer
Erling Poppe, but was heavily based on the BMW R75, manufacturing rights to
which had been offered to BSA as part of the war reparations. But while the
double-cradle frame and telescopic fork echoed the BMW, the engine unit was a
completely new design. Displacing 487cc, the engine was basically a parallel
twin not unlike that offered by the BSA A7, but it was housed in alloy castings
and turned around so that the crankshaft ran in line with the frame.
The first of the Sunbeam's problems arose from
the choice of transmission. The intention was to use a shaft drive like the BMW,
but the design adopted had a worm gear in place of the German machine's bevels.
While easier to manufacture, it
was inherently weak, and on prototypes || the worm stripped its thread if the 9
engine was fully used. The second problem was vibration.
This had been evident on the prototypes, but the
signs were ignored until the bike went into production in 1946. When an initial
batch was despatched to a police team intended to escort King George VI, it was
reported that they were unridable.
The machine weighed more than 4001b - but looked
heavier. Fitted with I6in 'balloon' tyres, its handling was prone to vagueness,
which became aggravated as the plunger rear suspension units wore. The finish,
in BSA's rather drab 'Mist Green', can hardly have helped its showroom appeal,
any more than the stories of its mechanical defects, and it was a poor seller.
In 1949 BSA decided to tackle both the performance and the styling by launching
the new S8 as a sports alternative to the touring S7. Lighter than its
predecessor, this used cycle parts such as forks and wheels from other BSA
models. It was a more popular machine than the S7, but was still no runaway
success. BSA finally discontinued the Sunbeams
Sunbeam S8 (1952)
Years in production: 1946-56 Engine type: parallel twin (in-line) overhead-cam
four-stroke Bore and stroke: 70 x 63.5mm Capacity: 487cc Power: 24 bhp @ 6000rpm
Carburettor: Amal Tyres (front/rear): 4JA x I6in/
43Ax I6in Wheelbase: 57in Weight: 4301b (S7) 4131b (S8) |
