A late 1961 BSA C.15T, built to a 1962 alloy-tank model aspect from parts.
The engine is in an Enduro state of tune, and features the last and strongest of the radial-feed crankshaft assemblies, running on a timing-side needle-roller main bearing. The conrod has been lightened and polished, an the cylinder bored out to 71mm. The compression ratio is 8.04:1 , a nice compromise between performance and longevity. The cylinder head has been gas-flowed to accept a 1" bore Monobloc carburettor; the rockers, which have been lightened and polished , run between bronze spacers on the rocker-shafts.They also use mushroom-headed adjusters for better valve-stem contact. The camshaft is the standard BSA sports item , as originally fitted, and retains the original low-radius followers.
The electrical system has been uprated to 12 V, and the ignition system uses a Lucas TAC5 transistor-assisted contact-breaker arrangement that necessitated a change to negative earthing. The headlight uses a 50W Lucas sealed - beam unit of 5" diameter.
The design brief was to produce a merry little snapper of a bike, with both off-road and back-lane capability, as well as the ability to cover distances if need be .
It's also rather pretty .....