BSA Thunderbolt
Encyclopedia
The BSA Thunderbolt was a British
motorcycle
made by BSA
at their factory in Armoury Road in Small Heath
, Birmingham
between 1964 and 1972. Fitted with a single carburettor it was capable of over 100 mph (44.7 m/s).
The BSA development team decided to keep costs down by re-using the well proven single sided front brake from the BSA Gold Star
and the same full race camshaft as the BSA Lightning
. Fitted with 12 volt electrics, a Zener diode
voltage regulator and twin coil ignition, the Thunderbolt sold well in the important US import market and with the 3.5 gallons (15.9 l) fuel tank gave a range of 210 miles (338 km).
From 1968 the Thunderbolt benefited from a number of minor improvements including a longer kick start to make starting easier and metal tank badges to replace the earlier plastic ones, which had a tendency to crack. An Amal Concentric Float carburettor dealt with the problems of fuel flooding experienced with the earlier monobloc carburettor, by having the float bowl arranged centrally around (concentric with, hence the name) the main jet to remove the sensitivity to fuel surge inherent an all the earlier designs. Stiffer suspension improved cornering but poor quality control and production problems on the BSA assembly line with later models led to oil leaks and rusting parts which damaged the reputation of the Thunderbolt, which was already struggling to compete against the emerging Japanese motorcycles of the early 1970s (such as the Honda CB750
) and production ended in 1972.
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
motorcycle
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
Birmingham Small Arms Company
This article is not about Gamo subsidiary BSA Guns Limited of Armoury Road, Small Heath, Birmingham B11 2PP or BSA Company or its successors....
at their factory in Armoury Road 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...
between 1964 and 1972. Fitted with a single carburettor it was capable of over 100 mph (44.7 m/s).
Development
The BSA Thunderbolt was designed as a touring motorcycle. A traditional air cooled 650 cc twin cylinder with a single large bore Amal Monobloc carburettor, it did not suffer from the same level of vibration as earlier BSA twins and could comfortably cruise at 70 mph (31.3 m/s). and reached over 100 mph (44.7 m/s). in road tests.The BSA development team decided to keep costs down by re-using the well proven single sided front brake from the BSA Gold Star
BSA Gold Star
The Gold Star is a motorcycle made by BSA from 1938–1963. They were 350 cc and 500 cc single-cylinder four-stroke production motorcycle known for being among the fastest bikes of the 1950s...
and the same full race camshaft as the BSA Lightning
BSA Lightning
The Lightning was a BSA motorcycle made in Birmingham between 1965 and 1972.-Development:The BSA Lightning was designed as the all-round sportbike of the 1960s, planned largely for export to the US market to complement the touring Thunderbolt and the supersports Spitfire...
. Fitted with 12 volt electrics, a Zener diode
Zener diode
A Zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage" or "Zener...
voltage regulator and twin coil ignition, the Thunderbolt sold well in the important US import market and with the 3.5 gallons (15.9 l) fuel tank gave a range of 210 miles (338 km).
From 1968 the Thunderbolt benefited from a number of minor improvements including a longer kick start to make starting easier and metal tank badges to replace the earlier plastic ones, which had a tendency to crack. An Amal Concentric Float carburettor dealt with the problems of fuel flooding experienced with the earlier monobloc carburettor, by having the float bowl arranged centrally around (concentric with, hence the name) the main jet to remove the sensitivity to fuel surge inherent an all the earlier designs. Stiffer suspension improved cornering but poor quality control and production problems on the BSA assembly line with later models led to oil leaks and rusting parts which damaged the reputation of the Thunderbolt, which was already struggling to compete against the emerging Japanese motorcycles of the early 1970s (such as the Honda CB750
Honda CB750
The Honda CB750 is a motorcycle built in several model series between 1969 and 2003 and 2007 that is recognized as a milestone for Honda's successful introduction of a transverse, overhead camshaft inline four-cylinder engine that has ever since been the dominant sport bike configuration...
) and production ended in 1972.