AJS 1931 S9 500cc 1 cyl sv



 AJS 1931   model “ S9 Light”  498 cc side valve  frame & engine #  S9L 133631

1928 is the last year that AJS motorcycles use flat tanks, in 1929 saddle tanks are introduced and consequently motorcycles suddenly get “modern” looks.  
The 1931 range  consists of  9  basic models, ranging from a 248 cc OHV single to a 996 cc V-twin machine intended for sidecar use. 
For the connoisseurs there are two OHC racing models  with capacities of 346 and 495 cc. 
Both inclined and vertical engines are available.  The “S9”  is available in two versions,  “ Light” and “ Heavy”. 
There are quite a few distinctions between the “L” and the “H”: different  gear ratios,  rear chain size, wheel base and petrol and oil tank capacity. 
These differences  make that the “L” is 15 lbs. lighter than the “H”.  
The engine is the same in both versions, it’s a sturdy design with bore x stroke of 84x 90 mm. 
The big end runs on roller bearings, the main shafts on ball bearings. 
The Amal carburettor is operated by twist grip control, a practical novelty in the early thirties.  
This machine is well-restored and a good runner.