The Birmingham Small Arms Company dates all the way back
to 1861, when a group of Birmingham gunsmiths came together to address
threats from both Royal Enfield and foreign gun makers. The plan was to move
from hand-crafted weapons to mass-production (and funding it the reason they
came together), and the quality of the items they produced would become a
hallmark of the company. They first diversified into pedal bicycles, and
bicycle components, then launched its first motorcycle in 1910. The company
was established at Armoury Way, Small Heath, just to the South-East of
Birmingham city centre, and after the Second World War this site was turned
over exclusively to motorcycle production.
After the First World War, and through the Second (in which it was the only
UK-based manufacturer of guns), BSA Cycles became the most popular British
bike manufacturer by volume, being particularly popular with fleets – BSAs
transported the majority of the Post Office telegram riders, and AA
attendants. Between the Wars, they used the advertising slogan “one in four”
to claim their dominance of the market. BSA also produced three-wheeled
light cars, and created Carbodies, manufacturers of the iconic London black
cab. It also expanded by regular acquisitions, including Daimler (1910),
Lanchester (1931), Sunbeam (1943) and Ariel (1944). In 1951 they purchased
Triumph motorcycles, making BSA Motorcycles (now separated from the bicycle
division) the largest motorcycle manufacturer in the world.
From there, the story is at the heart of the decline in British
manufacturing. A series of poor strategic decisions, a failure to recognise
where the motorcycle market was headed, and notoriously the failure to
recognise the Japanese threat meant BSA-Triumph went into steep decline. By
1972, it needed a bail out from the Heath government, but the price was a
merger with the equally moribund Norton-Villiers (itself the home of Norton
and JAP), a division of Manganese-Bronze Holdings. The new
Norton-Villiers-Triumph was established from the combined motorcycle
divisions, with the rest going to Manganese-Bronze. Optimistic export plans
were made, but the writing was on the wall. In 1975 the Wilson government
called in a loan and ended the party once and for all.
Three engines are referenced in period. Records are often unclear on which
were used, although one clue would be the second exhaust on the port side.
The A7 (after the motorcycle of the same name) Twin
The original 495cc engine appeared in 1946 (although it had been ready for
production before the War. Production (petrol) performance was 26bhp. It
used cast iron, air-cooled barrels as a single unit. Valves were operated by
a single cam behind the engine, driven off a long pushrod running inside the
block. It used a separate gearbox (as most other engines of the time), but
did use a primary chain tensioner to avoid rocking the two apart. Sparks
were produced by a single Lucas magneto. On the down side, the engine used
many long and inaccessible bolts to hold the top end elements down, and oil
leans were something of an occupational hazard.
The A7 Star Twin
In 1950 the original A7 engine was replaced with a 497cc version, derived
from the 650cc A10 (which had been developed from the original A7).
Outwardly similar to the A7, changes were significant. As well as the slight
increase in capacity, compression ration was raised, and a series of smaller
changes were made. In road trim the engine gained twin carburettors.
Production performance increased to 30bhp on petrol.
The Gold Star Single
The Gold Star motorcycle was originally produced as a celebration of Wal
Handley lapping Brooklands at over 100mph on a BSA in 1937 (for which he
received a Gold Star pin). Gold Stars would be the blue riband of BSA
motorcycles, comparable to Norton’s Manx – as with the Manx, buyers could
choose from a range of specifications from fast road to full race (and
including trials and scrambling model), each engine was hand built to order,
and supplied with dynamometer chart as proof of performance.
The first 500 Gold Star engine (model type B34) would appear in 1949 – BSA’s
plan had been that the twin would be their lead competition engine, but
development troubles meant engine man Jack Arnott was tasked with developing
a larger version of the 350cc Gold Star motor. This was a 499cc
single-cylinder engine, air-cooled but alloy construction (both barrel and
head). As with the A7, it used a separate gearbox, but unlike the A7 did not
have a chain tensioner. Engine developments were fairly limited over the
Formula III era:
1952: A new cylinder head design
1954: (CB34 model type) stronger crank, shorter con-rod, oval flywheel
revised valve gear, more finning
1955: (DB34 model type) better oil feed to the crank
This last model used a 85mm bore and 88mm stroke, with a 9:1 compression
ratio (for petrol). Advertised performance was 42bhp @7,000rpm (although
this would depend on chosen build specification) - contemporary
Norton Manx engines were producing 45bhp upwards.
We have no data for methanol-based performance.
Given the performance of both engine types, usage is surprisingly slim.
Whilst the Norton may have had the edge on outright power, the Gold Star was
close enough to win the Manx TT on several occasions. BSA’s forte was in
trials and scrambling, suggesting a particularly tractable motor, which
might have suggested it as a fine alternative to the JAP
on hills and for club racers. Perhaps cost and weight of numbers did it for
the BSA option.
Ken Wharton held high hopes for the A7
engine when he first ran his own special, then a Cooper in 1948-1951. But
success was limited (barring a win at Zandvoort in June 1950), with engine
problems often bringing and end to the day’s play. It was also used
Jan Flinterman in Belgium, while a Gold
Star was the original choice for the CRM in 1951.
Momentum seemed to be growing in 1951, especially as Norton’s Bracebridge
works strangled the supply of engine to Formula III drivers. The CRM
appeared with a Gold Star engine, then later the
Mezzolitres, with A7 Star motors.
Then in later 1952, when Cyril Kieft was moving up
to Wolverhampton, BSA man Billy Nicholson entered the story. A very
successful trials rider and scrambler (and sometime racer) for BSA, Billy
worked as an engineer for the company – he was actually on chassis &
suspension rather than engines. In 1952 Billy was invited to drive the works
Kieft (provided, of course, he supplied his own top-notch Gold Star). He
continued to drive in 1953 with moderate success, but while it might have
been expected to open the floodgates, the exact opposite happened. The
engine was not seen again