1912 3½ hp Zenith-Gradua JAP
July 9th, 2008
Newly arrived on display, this beautifully restored 1912 Zenith was an ultimate racer of its time. Powered by a 500cc vertical overhead valve JAP engine of the type that won the first Tourist Trophy race in 1907, it has Zenith’s innovative Gradua gearing system giving any ratio from 10: 1 to 4:1 at the turn of a handle. As the engine pulley size changes, the rear wheel moves in the frame to maintain constant drive belt tension.
Zenith-Gradua machines were so good at hill climbing that 16 British clubs banned them from competitions in 1910. The company turned this to its advantage by using ‘Barred’ as an advertising slogan and even exhibiting a machine caged behind bars at a London Show.
