Douglas 1920 4 hp 600 cc 2 cyl sv

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Douglas 1920  4 HP      596 cc  flat twin       frame#13014   engine # 12041    

 

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 not many changes were made;  a notable change for 1920 was  the introduction of a dry multi-plate clutch on the gearbox. 
The 4HP disappeared from the range in 1924. 
This machine is unrestored and  with it comes a not-quite-complete sidecar ( with newly made body)  and ditto spare engine.  
Accessories are a pillion seat and a bulb horn.