Donovan, in concert with Bill Mansell, had by 1913 begun to modify the Norton TT model into the Brooklands Special racer, with a guarantee that the engine had exceeded 65m/ph for one lap at the track. Each fast engine was installed in a slave chassis. That test chassis, having housed so many quick and famous engines, gained the name Norton Old Miracle. The Norton BS motorcycle weighed just over 90kg.



The science of combustion chamber shape, inlet and exhaust porting, compression ratios, cam profiles, and carburation were all in their infancy, and the best tuned Norton engines came from variations in the iron foundry process, rather than some intentional series of modifications to a standard motors. Some engines simply went better than others, and the quickest engines made their way to the racing team, or to selected tuners at Brooklands Special. More specs and user manual of Norton BS you can see in next overview.