4G Square Four Mark I

1951 Ariel 4G Square Four Mark I Technical Analysis & Specification Breakdown

Engineered by Ariel for the allround motorcycle segment, the 1951 Ariel 4G Square Four Mark I utilizes a 995 cc (60.7 cu in) air-cooled square four cylinder layout. In factory specification, peak output is rated at 35 HP (25.5 kW) at 5,500 rpm, transferring power to the rear wheel through a 4-speed gearbox and chain final drive. With a specific output of 35.2 HP per liter, the engine character is prioritizing low-RPM tractability, mechanical longevity and relaxed throttle response over peak redline numbers.

On the scales, the 4G Square Four Mark I measures 197 kg (434 lbs) dry, translating to a power-to-weight ratio of 0.18 HP/kg (5.63 kg per horsepower). Rider ergonomics and chassis geometry center around a 1,422 mm (56 in) wheelbase engineered for balanced agility and highway composure. The 16-liter (4.2 US gal) fuel tank supports practical everyday commuting and weekend road stints, while factory top speed is listed at 145 km/h (90 mph).

Within MotoLibrary's Ariel archive, this model family spans 5 indexed model years from 1949 to 1953, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.