572cc BSA B.50 Street Scrambler

A very interesting and potent machine, it originated as a B.50 T, but now has a full-race 572cc engine, running through a standard-bore header pipe into a very heavily modified black-box exhaust that retains its outward appearance, yet offers much improved gas-flow and resonance characteristics without a significant noise penalty.
The engine work included resleeving the cylinder, boring the crankcase mouth to suit, and opening the cylinder bore to 90mm while retaining the original 90mm stroke. The crankshaft is fitted with a Carrillo con-rod, and the after-market piston has been machined to give a compression ratio of 10:1. The head has been gas-flowed to 32 mm on the inlet side,twin-plugged, and has the option to run a much larger diameter header pipe if a rise in peak-torque rpm is required.

The camshaft is a Joy 200 item, using high-radius followers rather than the original flat items.
In order to obtain better control of the fairly heavy valves at higher rpm, R&D springs and titanium valve collars are used, with the rockers being held between bronze spacers on the rocker-shafts.
Ignition is by a Lucas RITA system, using a Dyna twin-exit 3-ohm coil .
The clutch has been uprated to cope with all of this.
A very standard looking machine, but with distinctly non-standard levels of acceleration, braking, and amusement.

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