Ariel Motorcycles

The Ariel Square Four with a 500 cc engine designed by Edward Turner first appeared for the 1931 season. Around this time the company went into receivership and then a new company was formed. The Square Four displacement was increased to 600cc. Throughout their history, the Square Fours had overheating problems with the rear cylinders which resulted in distorted heads. A redesign in 1937 resulted in a 995 cc OHV version designated the 4G. In 1939 Anstey-link plunger rear suspension was an option. It was still available when production restarted in 1946, with telescopic forks replacing the girder forks.