BSA B50
Encyclopedia
The BSA B50 is a motorcycle
made by BSA at their factory in Small Heath
, Birmingham
. The last of the big capacity unit singles from the Birmingham Small Arms company, it had a 499 cc alloy engine with a bore of 84 mm (3.3 in) and a stroke of 90 mm (3.5 in), a short wheelbase and unusually high centre of gravity. As well as the road going version, special models were produced for off road competition use.
About 5,700 were built, but few survive in original condition as many were modified for off road use by specialist builders such as Eric Cheney
.
of Hereford England and ridden by Nigel Rollason and Clive Brown won the 500 cc class in both the Thruxton 500 miler and the Barcelona
24 hours ( at the Montjuïc circuit
), and won the Zolder 24 hour race outright. Also, a B50 fielded by Mead & Tomkinson once held the class lap record in the Production TT
.
After the demise of BSA, Alan Clews bought up remaining B50 part stocks and set up Clews Competition Motorcycles
, producing successful scramblers based on the B50.
and the Barcelona 24 hour endurance race.
using two B50 engines in 1977. The frame was a slimline featherbed
Norton Atlas
. Triumph considered putting the B100 into production but were not able to finance re-tooling costs.
The B100 prototype was ridden for two years has stored since but was featured in the magazine British Bike Mechanics in April 1978 and January 1988.
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
made by BSA at their factory in Small Heath
Small Heath, Birmingham
Small Heath is an inner-city area within the city of Birmingham, West Midlands, England. It is situated on and around the A45 ....
, Birmingham
Birmingham
Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...
. The last of the big capacity unit singles from the Birmingham Small Arms company, it had a 499 cc alloy engine with a bore of 84 mm (3.3 in) and a stroke of 90 mm (3.5 in), a short wheelbase and unusually high centre of gravity. As well as the road going version, special models were produced for off road competition use.
Development
The B50 included many new features such as oil in the Frame technology and the electrics in a single removable 'pod' - ideas that were quickly picked up by the Japanese competition. BSA needed to keep production costs down and made use of as many existing factory parts as possible, such as the unit single crankcases from the older 250cc engine. This meant that the B50 required very careful assembly of crankcase and rocker box gaskets and seals to avoid oil leaks. The extra torque of the B50 also led to slipping of the standard BSA clutch and riders often modified it by adding an extra friction plate and stronger clutch springs. The ignition coils used on many production B50 models were also salvaged parts and led to difficulty starting and erratic slow running.About 5,700 were built, but few survive in original condition as many were modified for off road use by specialist builders such as Eric Cheney
Eric Cheney
Eric Cheney was an independent British motorcycle designer and constructor. He was known as one of the best motorcycle frame designers of his era.-Early life:...
.
Racing success
B50 bikes were successful in both road-racing and off-road events. In particular, a modified B50 Gold Star 500 entered by Mead & TomkinsonMead & Tomkinson racing
Mead & Tomkinson was a car and motorcycle dealership in Hereford and Tewkesbury. Three of the Tomkinsons, sons Chris and Patrick, and their father, Mike, successfully built and fielded racing motorcycles. They concentrated on the Isle of Man TT and on 24-hour and 8-hour endurance races at Spa,...
of Hereford England and ridden by Nigel Rollason and Clive Brown won the 500 cc class in both the Thruxton 500 miler and the Barcelona
Barcelona
Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...
24 hours ( at the Montjuïc circuit
Montjuïc circuit
The Montjuïc circuit is a former street circuit located on the Montjuïc mountain in Barcelona, Catalonia, Spain. It is considered among the best Formula One circuits of all time, with Autosport rating it among its ten best for their 50th anniversary of Formula One issue...
), and won the Zolder 24 hour race outright. Also, a B50 fielded by Mead & Tomkinson once held the class lap record in the Production TT
Isle of Man TT
The International Isle of Man TT Race is a motorcycle racing event held on the Isle of Man and was for many years the most prestigious motorcycle race in the world...
.
After the demise of BSA, Alan Clews bought up remaining B50 part stocks and set up Clews Competition Motorcycles
Clews Competition Motorcycles
Clews Competition Motorcycles or CCM for short, is a British motorcycle manufacturer based in Bolton, England.-History:CCM was born out of the collapse of BSA's Competition Department in 1971....
, producing successful scramblers based on the B50.
B50 SS (Street Scrambler)
The BSA B50 SS 'street scrambler' was designed for on-road use and was aimed at the US export market and proved its credentials by winning the 500cc class in the Thruxton 500 milerThruxton 500
The Thruxton 500 is a 500 mile motorcycle endurance race held at Thruxton Circuit, near Andover in Hampshire, United Kingdom, which is the fastest racetrack in the country...
and the Barcelona 24 hour endurance race.
B50 MX (Moto Cross)
The B50 MX was designed for off road competition and produced between 1971 and 1973. The very last MX's produced were therefore coming off the production line after the demise of BSA and were 'badged' as the Triumph TR5MX.B100 V TWIN (2 B50 Cylinders )
Specialist motorcycle designer Gerald Fitzpatrick created a 1,000 cc BSA V-twinV-twin
A V-twin engine is a two-cylinder internal combustion engine where the cylinders are arranged in a V configuration.- Crankshaft configuration :Most V-twin engines have a single crankpin, which is shared by both connecting rods...
using two B50 engines in 1977. The frame was a slimline featherbed
Featherbed frame
The featherbed frame was a motorcycle frame developed by the British Norton motorcycle company to improve the performance of their racing motorcycles around the twisting and demanding Isle of Man TT course in 1950. It was considered revolutionary at the time, and the best handling frame that a...
Norton Atlas
Norton Atlas
The Norton Atlas was a Norton motorcycle made by between 1962 and 1968, until it was replaced by the Norton Commando.-Development:The Mark 1 Atlas was launched as the 750SS in the early 1960s. Designer Bert Hopwood’s 497cc Dominator engine was bored and stroked out to 745cc, via 600cc and then...
. Triumph considered putting the B100 into production but were not able to finance re-tooling costs.
The B100 prototype was ridden for two years has stored since but was featured in the magazine British Bike Mechanics in April 1978 and January 1988.