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BSA C15

Make Model	BSA C15, C15SS, C15T, C15S
Year	1958 - 67
Engine	Four stroke, single cylinder, OHV
Capacity	249 cc / 15.2 cub in.
Bore and Stroke	67 x 70 mm
Compression Ratio	C15, C15T: 8.0:1 C15SS: 8.75:1 C15S: 10.0:1
Cooling System	Air cooled
Oil Capacity	C15, C15SS: 2.25 L / 4.76 US pints C15T, C15S: 2.75 L / 5.8 US pints
Carburetor	Amal
Exhaust	Single, steel, chrome
Starting	Kick start
Spark Plug	C15, C15T: Champion N5, gap 0.020 in. C15SS: Champion N4, gap 0.020 in. C 15S: Champion N3, gap 0.020 in.
Battery Capacity	13 Ah
Max Power	11 kW / 15 hp @ 5000 rpm
Clutch	4 Friction plates
Transmission	4-Speed
Final Drive	C1C5, C15SS: Chain, 112 pitches C15T, C15S: Chain, 123 pitches
Gear Ratios	C15: 1st 15.98 / 2nd 10.53 / 3rd 7.66 / 4th 5.98:1 C15SS: 1st 12.63 / 2nd 9.91 / 3rd 7.19 / 4th 5.98:1 C15T: 1st 28.53 / 2nd 22.05 / 3rd 14.67 / 4th 9.0:1 C15S: 1st 19.0 / 2nd 14.94 / 3rd 10.8 / 4th 9.0:1
Frame	Single loop with twin rails under engine
Steering Head Angle	C15, C15SS: 65° C15T, C15S: 63°
Steering Lock Angle	C15, C15SS: 50° C15T, C15S: 60°
Front Wheel Travel	127 mm / 5 in
Rear Suspension	Pivoted fork
Rear Wheel Travel	63 mm / 2.5 in.
Front Wheel	C15, C15SS: WM1-17 C15T, C15S: WM1-20
Rear Wheel	C15, C15SS: WM2-17 C15T, C15S: WM3-18
Front Tyre	C15, C15SS: 3.25 x 17 in. C15T, C15S: 3.00 x 20 in.
Rear Tyre	C15, C15SS: 3.25 x 17 in. C15T, C15S: 4.00 x 18 in.
Front Brake	6.5 in., drum
Rear Brake	6.5 in., drum
Dimensions	Length: C15, C15SS: 1981 mm / 78.0 in. C15T, C15S: 2045 mm / 80.5 in. Width: C15: 660 mm / 26 in. C15SS: 686 mm / 27 in. C15T, C15S: 800 mm / 31.5 in. Height: C15: 940 mm / 37 in. C15SS: 914 mm / 36 in. C15T: 1067 mm / 42 in. C15S: 1054 mm / 41.5 in.
Wheelbase	C15, C15SS: 1308 mm / 51.5 in C15T, C15S: 1314 mm / 51,75 in.
Ground Clearance	C15, C15SS: 127 mm . 5 in. C15T: 191 mm / 7.5 in. C15S: 178 mm / 7 in.
Seat Height	C15, C15SS: 762 mm / 30 in. C15T: 838 mm / 33 in. C15S: 813 mm / 32 in.
Dry Weight	C15, C15SS: 127 kg / 280 lbs C15T, C15S: 120 kg / 265 lbs
Fuel Capacity	C15: 11.5 L / 3.0 US gal C15SS: 13.6 L / 3.6 US gal C15T, C15S: 9.4 L / 2.5 US gal

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 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 left 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.