1959 Ariel Square Four MKII

The Ariel Square Four was a British motorcycle built between 1931 and 1959. The Square Four’s Mark II production model, also known as the MKII, was manufactured from 1953 to 1959 by motorcycle designer Edward Turner, who would later become well-known for his work with Triumph motorcycle engines. The Square Four MKII is known for its uniquely designed 997cc four-stroke engine that utilizes transverse crankshafts, as well as its “plunger” style rear suspension.

Capable of exerting 40 horsepower and reaching speeds of up to 100 mph, the MKII differs from its predecessor models with a redesigned frame to provide clearance for its high-mounted SU carburetor. The MKII’s unique design also utilizes separate barrels, a redesigned cylinder head with four separate exhaust pipes extending out from two cast-aluminum manifolds, and a rocker-box combined with the inlet manifold.

The Square Four was designed to be more of a cruiser more than a racing bike. The dual-crankshaft system made for a smoother ride and also made it capable of maintaining cruising speeds for longer distances. 3,828 of these ingenious Square Four MKII models were manufactured during their six-year production period. This specific MKII has been painstakingly restored from the ground up by the experts at Retrospeed in Belgium, WI and is now available for viewing at Throttlestop's Motorcycle Museum. It is believed to be one of the very last Square Four MKII models imported into the United States.

Located in Elkhart Lake, Wi, just a few miles outside of Road America Racetrack, Throttlestop is a premier destination for car and motorcycle enthusiasts of all backgrounds. Whether there to buy luxury cars or take in the incredibly rare pieces of the Motorcycle Museum, all visitors are welcome to experience how Throttlestop is Driven By Passion.