Zenith 1912 Gradua 500cc 1 cyl sv 2603



Zenith 1912   3 ½ HP  488 cc JAP    single     frame #  1620,  engine # 14227 

Zenith’s chief Engineer Freddy Barnes was responsible for the famous “Gradua” gear. 
The mechanics of the Gradua  gear were a variable engine pulley worked by a handle, with simultaneous correction of the belt length made by sliding the rear wheel backwards or forwards in the fork slots.
Its advantage showed itself most effectively in speed hill climbs.
The Zenith rider could change during the journey up while the other competitors had to make do with a single choice of gear ratio.
Rival riders and manufacturers thought that this was an unfair advantage so many leading clubs barred Gradua gear Zeniths from their hill climbs. 
Zenith was quick to recognize the publicity value and took the word “barred” as their trademark.
The 1912 range consisted of a 3 ½ HP single  (bore x stroke 85.5 x  and a  6 HP twin, both powered by an engine of Prestwich design. 
Among the improvements  for 1912 were  a quickly detachable rear wheel and a graceful aluminium  cover to the gear-operating chain between the sprockets.
This technically highly interesting machine  is fitted with Miller bulb horn, Bosch magneto  and Brown & Barlow carburettor and comes complete with Pioneer Certificate