1939 Ariel Square Four

1939 ARIEL SQUARE FOUR BACKGROUND
The original Square Four was conceived by legendary motorcycle designer, Edward Turner, who later created the game-changing Triumph parallel twin. His original design for the Square Four was an OHC (Overhead Cam) design with a displacement of 500cc when it debuted in 1931. However, constant overheating problems with the rear set of cylinders forced two redesigns, the latter being a total clean-sheet design. This new Square Four ditched the OHC for simpler OHV (Overhead Valves, ie: pushrods and rocker arms) and pushed the displacement all the way out to 1000cc. It launched in 1936 as the model 4G, and this 1939 Ariel Square Four is a fine example of the 4G. It would also be the last year of civilian production until after the end of World War II.

1939 Ariel Square Four SPECIFICATIONS

Engine type Displacement Bore & Stroke Compression ratio Fuel system Engine output Top speed Wheelbase Length Dry weight Primary drive Clutch Gearbox Final drive Frame type Front suspension Rear suspension Brake, front Brake, rear Tire, front Tire, rear Air-cooled OHV square 4-cyl w/2 crankshafts 997cc / 60.84 ci 55.0mm X 78.0mm / 2.60" X 3.10" 6.0:1 Single carburetor, SU MC2 35 hp @ 5500 rpm 87 mph / 146 km/h 56.0" / 1422mm 82.0" / 2983 425 lbs / 193.0 kg Chain Multi-plate, wet 4-speed constant mesh, right-foot shifting chain Steel tube single loop Girder Austey-type plunger 7-inch (178mm) SLS drum 7-inch (178mm) SLS drum 3.25" X 19" (3.25-19) 4.00" X 18" (4.00-18)

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Check out these ARIEL BOOKS





Ariel: The Complete Story (Crowood Motoclassics)



Ariel Square Four 1948 Limited Edition Extra 1959



Ariel Square 4 (Super Profile)



The Modern Ariel Motor Cycle - 1939-47 Owners' Guide Single Cylinder Models



Ariel Motorcycles Workshop Manual 1933-1951



Book of the Ariel Leader and Arrow 1958-1966



115MPH ARIEL Motorcycle Conversion Article.: Motorcycle Mechanics March 1966.



Aurora to Ariel: The Motorcycling Exploits of J.Graham Oates, Pioneer Motorcyclist



BOOK OF THE ARIEL 4 STROKE SINGLES 1939-1960



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Back to top 1939 Ariel Square Four
Last updated 1/1/18

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