Manufacturer United Kingdom BSA Also called 'Star' Production 1958–1967 Predecessor BSA C12 Successor BSA B25 Starfire, BSA C25 Barracuda Engine 4-Stroke 247cc OHV single cylinder Power 15bhp @5000rpm

The BSA C15 was the first four-stroke unit construction motorcycle produced by the British company BSA and manufactured between 1958 and 1967. At the time the C15 was the largest capacity bike that a learner could ride on L plates in the United Kingdom. As a result, many C15s had a reputation for being unreliable, as the learner riders would often push their machines to the limit.[1] The C15T Trials version also made the sport of motorcycle trials accessible to a much wider range of riders but the lack of power and issues with reliability meant that BSA could not compete against emerging Japanese motorcycles such as the Honda CB250 which began arriving in the UK in the 1960s Development

BSA acquired the Triumph marque at the start of the 1950s and the BSA C15 250cc four-stroke was derived from the 200cc Triumph Tiger Cub. 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 250cc 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 standard C15 Model was available in Fuchsia Red, Turquoise Green, Almond Green, Red, Black, Nutley Blue, Sapphire Blue and Royal Red.

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.[2] In 1965 the distributor was moved to the right on the whole range of BSA motorcycles.

During 1967 the 250cc 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 Transmission Four Speed Gearbox Wheelbase 51.25 inches (130.2 cm)