4G Square Four Mark II

1957 Ariel 4G Square Four Mark II Technical Analysis & Specification Breakdown

Built around Ariel's allround motorcycle platform, the 1957 Ariel 4G Square Four Mark II relies on a 995 cc (60.7 cu in) air-cooled square four cylinder powerplant. In factory specification, peak output is rated at 45 HP (32.8 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 45.2 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 II measures 197.3 kg (435 lbs) wet (curb), translating to a power-to-weight ratio of 0.23 HP/kg (4.38 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 18.93-liter (5 US gal) fuel tank paired with a rated consumption of 3.04 L/100 km provides an estimated theoretical range of roughly 623 km (387 miles) between fill-ups, while factory top speed is listed at 160 km/h (99 mph).

Within MotoLibrary's Ariel archive, this model family spans 7 indexed model years from 1953 to 1959, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.