BSA had acquired the
Triumph marque at the start of the 1950s and the lightweights
towards the end of the decade owed far more to Triumph
than to BSA. Chief among them was the 1952 C15 Star.
A 250cc fourstroke almost totally derived from the
200cc Triumph Tiger Cub. Even so the new model seemed
both up-to-date and sophisticated electrics. As with
its Triumph predecessors, the C15 and its derivatives
suffered from minor electrical problems, oil leaks
and somewhat complicated maintenance routines.
But it went well enough
and was mainly reliable. The SS80 sports version,
which appeared in 1961, was faster, while the 350
version, the B40, offered more power. In the mid 1960s
a similar engine layout was seen in the 75cc Beagle
and 50cc Ariel Pixie, two fatally flawed attempts
by the BSA Group to launch an ultra-lightweight.
Over the years there
were countless variations on the same theme, including
sports and off-road versions, while the basic engine
was stretched to 441 and finally 449cc. The enigne
even found its way back to Triumph, to power the street
scrambler styled singles of the late 1960s. The last
of BSA's C15 derivatives was the B50, built until
1973. Even after this, the specialist company CCM
of Bolton built their own derivative of the B50 for
off-road competition throughout the 1970s.
Off-road sport was long
a speciality of BSA. In the post-wat era the 350 and
500 Gold Stars had been enormously successful trials
and scrable mounts, but the company correctly anticipated
the shift towards lighter, more manageable machines.
The lightweight, unit-construction C15 offered a great
deal of potential and the competition shop soon developed
successful works specials ridden by expert rider and
BSA employee, Brian Martin.
followed the C15S scrambler and C15T trials machine.
Superficially similar to the roadsters there were
in fact numerous differences which included frames,
wheels and suspension, as well as a host of engine
and gear modifications.
The competition bikes
succeesed famously. On the 441cc derivative, Jeff
Smith won the world motocross championship in 1964
and 1965. It was the designers finest hour.