Douglas 1922 4HP 600cc 2 cyl sv 2610



Douglas 1922  4 HP      596 cc   side valve flat twin       frame# 13865   engine # 13848    

This Bristol-based firm developed the horizontally opposed fore-aft unit in about 1907 and continued utilising this engine layout  well into the thirties. 
The earliest Douglas models had direct belt drive, but in 1910 a two-speed gearbox was added, with the control on top of the petrol tank. Douglas machines became very popular because of their lightness,  ease of starting and speed: in the 1912 Junior TT races Douglas took first, second and fourth places. 
In the First World War  thousands of  2 ¾ HP machines were commissioned for use by despatch riders and  performed splendidly. 
In 1915 a 596 cc model was introduced to cater for  the need for a more powerful sidecar puller. 
A notable difference in engine design with the     2 ¾  HP model is the wet sump oiling system.  
A year later the 4 HP model was improved in a number of ways. 
To mention a few: other front forks, new design of exhaust, frame  and tank alterations, front and rear brake changes, many  small engine design improvements. 
To sum it up: quite another machine! Between 1916 and 1921 hardly any changes were made. 
At the 1921 Olympia Show the company remarked: “ The 4HP Douglas remains practically unaltered for the experience gained during the war under extremely unfavourable conditions has made the machine eminently satisfactory in its present form.” The 4 HP disappeared from the range in 1924. 
Bore x stroke are 74.5 x 68 mm, petrol capacity 9 litres, oil capacity 4 litres.  
Petrol consumption is given as  circa 1 litre per 25 kilometres and the machine weighs 120 kgs. 
This finely restored machine comes complete with Lucas acetylene lighting and bulb horn .