English Model A's and early US models
have the same dimensions.
Bore 2.5". Stroke 2.75". Capacity 13.5 cu.in.
Compression ratio (simple) 3.8:1 (actual) 2.88:1
Early US models have just one brake, a left-foot
operated drum brake in the rear wheel. The English
Model A has the same drum brake, plus a contracting-band
brake on the countershaft operated by a lever
on the right handlebar.
English Model B's
Bore 70mm. Stroke 74mm. Capacity 285cc.
Compression ratio (simple) 5:1 (actual) 4.05:1
These are identified by the removable cover
on the transfer port on the right hand side
of the cylinder, with an entwined "S S" on it.
There are two drum brakes, both on the rear
wheel. The left one is foot-operated, the right
one by a lever on the right handlebar.
US models from late 1924
Bore 2.625". Stroke 2.875". Capacity 15.5 cu.in.
These can be easily identified as they have
vertical fins on the top of the cylinder. (Earlier
ones have horizontal fins.) They also usually
have an engine number with a prefix B, but not
always. The crankcase is VERY different from
These models were also offered with the option
of a second rear drum brake, as on the English
English models have the inlet port at the REAR,
with the exhaust port on the
left hand side. US models have the inlet port
at the FRONT, with the exhaust port on the right
English models have a brass flywheel with flywheel
ignition up to number 3928. This is from an
original handbook, but it doesn't say whether
this is the chassis number or the engine number.
However, from checking on the numbers to hand,
it would suggest that this is the CHASSIS number.
From that number on, they have a steel flywheel,
with a chain-driven magneto situated on a platform
which replaced the older flywheel backplate.
I know of 7 bikes with this, and 4 of them have
very rare small Bosch FB1b magnetos, suggesting
that this was the usual magneto fitted. (The
other 3 had 3 different makes, and needed a
cut-out on the top cover.) I have an FB1b, and
also an FB1c which is identical in size. They
are small enough to fit under the top engine
cover without modification.
English Model A's have both electric and gas
lighting, with the electric lamp mounted on
the right mudguard stay and the gas on the left.
The rear lamp is electric and gas in the same
Early English Model B's have electric lighting
with a dry battery for parking lights, and later
ones, with magneto ignition, have gas lighting.
US models have Eisemann flywheel magnetos and
electric lighting. The later models have 10-pole
generators. Early models seem to have had twin
lights, later ones a single light mounted on
the front mudguard/fender.
Wheelbase 59". Later US models 56".
Seat height 27".
Weight approx 195lbs.
Tyres - US 26" x 3.00" English 26" x 2.5"
English Model C's have the Blackburne 350cc
4-stroke engines fitted, with a Sturmey Archer
3-speed gearbox, and conventional clutch. Dimensions
are the same, except for the weight, and the
tyres, which are 26" x 3.00".