These bikes represent the end of the era of big British singles, as when AMC merged with Norton production concentrated on twins.

The AJS was updated when a springer frame rear suspension was made available for 1949, to become the Model 18S.

The engine was released just postwar with a compression ratio of 5.9:1, necessary because of the low quality fuel available in Britain immediately after the War.

Post war petrol rationing continued until 1950 and it was several years before performance fuels were generally available in the UK.

The earlier model did not have a magdyno - the separate magneto was directly above the dynamo behind the cylinder.