Norton 1939 Big Four 633cc 1 cyl sv



Norton 1939  633 cc sv single   “ Big Four”   frame #  100351  engine # 91089

The model name Big Four was used from 1907 till 1954, when production of all side valve Nortons stopped. 
The model was mainly designed as a strong and reliable sidecar machine. 
In World War I many were supplied to the Russian army, and in World War II  the further developed Big Four did excellent service in the British army. 
Reliability and fuel economy are keywords for this Norton. 
It has the biggest capacity (with bore x stroke of 82×120 mm) and the lowest compression ratio( 1:4.5) in the pre-war  Norton range. 
Some of the new features  for 1939 are an improved oil control ring, more effective silencer, more comfortable saddle position, bigger saddle and polished engine and gearbox covers. 
This machine is a well maintained older restoration.