|Successor||BSA B25 Starfire, BSA C25 Barracuda|
|Engine||4-stroke 247 cc (15.1 cu in) OHV single cylinder|
|Power||15 bhp (11 kW) @5000rpm|
|Transmission||4 speed, chain drive|
|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 between 1958 and 1967, and was BSA's first four-stroke unit-construction bike. At that period, a 250cc was the largest capacity bike that a learner could ride on L-plates in the United Kingdom, the C15 was attractive to riders with provisional licences. An off-road version, the C15T Trials, gave riders access to the sport of motorcycle trials.
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 at the start in 1936, 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 to the crankshaft which had skew gears driving a shaft with the points at the top and the oil pump at the bottom. 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 C15 engine also exploited an advantage of being the biggest capacity motorcycle a learner rider in the UK could use before passing a motorcycle driving test.
The BSA C15 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 distributor sprouted from above the R/H side of the gearbox; but in 1965 the distributor was moved to the right side of the engine.
During 1967 the 250 cc C15 was replaced by the BSA B25 'Starfire' and BSA C25 'Barracuda' models, which had a quickly detachable rear wheel and 12 volt lights. The engine was also increased in capacity to 441cc develop 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 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 it was ideal for military use and was popular 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 1968 and 1970 with chrome mudguards and tank side panels.
The BSA C15P was a police model produced between 1963 and 1967.