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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.〔''Motor Cycle'', 22 April 1965, pp.508-511 ''C15 Riders Report'' collated by ''Mike Evans''. Accessed 2014-10-18〕 Producing only , the C15's lack of power 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. ==Development== 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.〔''Motor Cycle'', 29 July 1966, pp.112-113 ''Sturdier BSA two-fifties''. Accessed 2014-10-18〕 BSA marketed these larger machines with increased capacity of 441 cc as the BSA B44 Shooting Star and the BSA Victor Special.〔 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「BSA C15」の詳細全文を読む スポンサード リンク
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