|Manufacturer||BSA Motorcycles Ltd., Armoury Road, Small Heath, Birmingham, England|
|Parent company||Birmingham Small Arms Company|
|Successor||BSA B25 Starfire, BSA C25 Barracuda|
|Engine||4-stroke 249 cc (15.2 cu in) OHV single cylinder, alloy head, Amal 375 carburettor|
|Bore / stroke||67 x 70 mm|
|Power||15 bhp (11 kW) @7000rpm|
|Ignition type||Coil with 60 watt Lucas RM13 alternator|
|Transmission||4 speed, chain drive|
|Brakes||6 inches (15 cm) front and rear with full width hubs|
|Tyres||3.25 x 17" front and rear|
|Wheelbase||51.25 inches (130.2 cm)|
|Fuel capacity||3 gallons|
The BSA C15 was a 250 cc single-cylinder ohv motorcycle manufactured by the British company BSA from September 1958 until 1967, and was BSA's first four-stroke unit-construction bike. For most of that period, after the introduction of 'Learner Laws' in 1961, a 250 cc was the largest capacity solo machine that a learner could ride unaccompanied when displaying L-plates in the United Kingdom. A road-going Sports derivative was added in 1961, and off-road versions, for Trials and Scrambles, were also available in the range.
Producing only 15 bhp (11 kW), the C15's lack of power and issues with reliability meant that it was hard for the BSA to compete with the more sophisticated Japanese motorcycles (such as the Honda C71 and CB72) which began arriving in the UK in the 1960s.
BSA acquired the Triumph marque in 1951, and the BSA C15 250 cc four stroke was derived from the 200 cc Triumph Tiger Cub, itself coming from the 150cc Terrier. Edward Turner became head of the BSA automotive division and in 1958 BSA introduced the concept of unit construction, where the engine and gearbox were combined in one piece rather than as separate components. The BSA C15 'Star' was the first unit construction model and proved more reliable and economical than its predecessor, the pre-unit BSA C11.
The engine had an iron barrel and alloy head with overhead valves operated by pushrods which ran in a separate tube to fully enclosed rockers. The camshaft was geared directly from the crankshaft with skew gears driving the oil pump and the contact breaker assembly mounted behind the cylinder via a shaft. The alternator was to the left and the primary drive was via a duplex chain to a multi plate clutch. The four speed gearbox was at the rear of the vertically split crankcase. The frame was single loop with twin rails under the engine and pivoted fork rear suspension, and both wheels were 17 inch with full width cast iron hubs. An oil tank was under the seat on the right matched by a toolbox on the left. Between them was an ignition switch panel hiding the battery. The headlamp was fitted in a nacelle which also housed the instruments and switches as was fashionable at the time. Deeply valanced mudguards were fitted to the standard model, making it look heavier than it actually was.
The C15 also had a completely redesigned frame and the 250 cc engine did, however, require careful maintenance and as well as oil leaks and electrical faults there were problems with the gearbox, failures of the valve gear, weak big-end and problems with the adjustment of the clutch. Originally, the contact breaker housing was mounted rear of the cylinder above the gearbox, but was relocated to the right-side crankcase driven off the camshaft-end, accessed via a circular plate.
The later engines from 1966 also benefitted from rationalisation at BSA when the bottom-end – crankcases, bearings, oil pump with circulation system and gearbox components – were redesigned reflecting the development work in producing Jeff Smith's works Victor from the B40 basis. BSA marketed these larger machines with increased capacity of 441 cc as the BSA B44 Shooting Star and the BSA Victor Special.
BSA C15 'Sportsman' (SS80)
In 1961 the 'Super Sports' model (SS80) or C15 Sportsman joined the range, with a tuned engine, roller big-ends and lower handlebars. A faster 350 cc version, the SS90 based on the BSA B40 was also added to the range but was not a big seller to the general public – as it was too big for learners and too small for those who had passed their motorcycle test - but the B40 was ideal for military use including use with the British Armed Forces.
The BSA C15G was produced from 1966 to 1967 and was the last version of the C15 engine with the ball bearing timing side main bearing, roller drive side and strengthened crankcases, larger oil pump and needle roller gearbox layshaft bearings.
The BSA C15T was a trials version with a higher clearance frame fitted with a reinforced plate, special gear ratios suited to off-road use and a high level exhaust pipe. A special tank and optional lighting allowed it to be converted for legal road use.  The all-alloy engine had a special camshaft, and was specially tuned for off-road trials use. The C15T proved to be competitive at club and national levels, and it remained unchanged in the BSA range until 1965.
BSA C15T Trials Cat
The BSA C15S was the motorcross competition version of the 250 cc Star produced between 1959 and 1965. As with the trials version, the C15S saved the weight of a battery through an 'energy transfer' electrical system which was notoriously unreliable. The problem was that the timing and points gap required far too much careful setting for a rugged competition motorcycle. The scrambler C15 was unsilenced and had special tyres and strengthened fork springs with rubber fork gaiters to protect the seals.
BSA C15 Starfire
The BSA C15 Starfire Roadster was produced between 1963 and 1964 with chrome mudguards and tank side panels.
The BSA C15P was a police model produced between 1963 and 1967.
- Motor Cycle Data Book 1960, p.60 George Newnes Ltd., London. Accessed and added 2014-10-21
- Motor Cycle, 22 April 1965, pp.508-511 C15 Riders Report collated by Mike Evans. Accessed 2014-10-18
- Kemp, Andrew; De Cet (2004). Classic British Bikes. Mirco. Bookmart Ltd. ISBN 1-86147-136-X.
- Bacon, Roy (1988). British Motorcycles of the 60's. Osprey Publishing. ISBN 1-85648-166-2.
- Motor Cycle, 29 July 1966, pp.112-113 Sturdier BSA two-fifties. Accessed 2014-10-18
- "BSA C15T". Retrieved 2009-10-26.