600cc Side valve. This model was only
produced for one year, after this there
were big changes. In 1937 this bike had
an 85mm bore after 37 they had an 82mm
bore. The numbers are very low and was
one of the first 1000 bikes produced.
1948 BSA M21, 600cc
1951 BSA M21
1952 BSA M21
BSA introduced a new range of singles
in 1937 of which the M21 was one. It featured
a lazy 596cc sidevalve motor with huge
amounts of torque on tap and was squarely
aimed at the sidecar market. Along with
its close relative the 500cc M20 it was
an immediate success, and continued in
production through the war years and into
the fifties, by which time the 'girders'
had been replaced with telescopic forks.
