The first Ariel Square Four 4F was shown at the Olympia Motorcycle Show in 1930,[REF] in chain driven overhead-camshaft 500 cc form [REF]. Early Square Fours used a hand-change, four-speed Burman gearbox [REF].
In 1932, the cylinder bores were enlarged by 5 mm to give a capacity of 601 cc, specifically to accommodate owners who wanted a sidecar [REF].