c1956 Ariel Square Four Mk II 1000cc Motorcycle

Description

Ariel's legendary Square Four is the model most often associated with the Birmingham motorcycle manufacturer and its unique configuration set it apart from contemporary rivals. Tracing its origins back to the early 1930s, the Square Four was designed by the talented Edward Turner, who joined the company as a technician and went on to achieve even greater success with Triumph. After receiving approval from his boss Jack Sangster, Turner's radical new creation first entered production in 1931 and with four vertical cylinders arranged in a square configuration, air-cooling and overhead cams, this was no ordinary motorcycle. Initially of 500cc capacity, this was enlarged to 600cc for sidecar use in 1932 but the Depression hit Ariel hard and forced a major rationalisation of the model range, with both the overhead-valve Red Hunter and Square Fours sharing a common frame design thereafter. By the late 1930s further development saw the Square Four switch to an ohv design with the 1000cc Model 4G model of 1937. Once hostilities ceased after World War Two, the Square Four was put back into production and in 1949 the engine was further developed with cast alloy used for the block and cylinder head to reduce weight. Retrospectively dubbed the Mark I, these early post-war Square Fours were in turn superseded by the 'four pipe' Mark II in 1953, with a redesigned cylinder head and two separate exhaust pipes on either side of the motorcycle. These changes elevated the Square Four into the big league - the Ariel was now a genuine 100 mph motorcycle. Throughout the 1950s the Square Four continued to use the somewhat antiquated plunger frame before production ceased in 1959. Any Ariel Square Four is a highly desirable motorcycle and prized collectors piece, but the Mark II is particularly coveted for its fabulous performance.