Ariel Square Four (4G:1936-48MkI:1949-53MkII:1953-58)

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The Ariel Square Four was produced in three different versions, 4G, Mark I, and Mark II, from 1936 to 1958. The production numbers were 4,288 for 4G, 3,922 for Mark I, and 3,828 for Mark II. It had a four-stroke, vertical square four, overhead valve engine with eight valves and a capacity of 997cc. The compression ratio was 6.0:1, and the induction was through an SU carburetor. The bike had a kick start and a maximum power output of 26 kW / 35 hp at 5500 rpm for the 4G and Mark I versions and 34 kW / 45 hp at 5500 rpm for the Mark II version. The transmission was four-speed, and the final drive was through a chain. The bike had a single down tube frame, telescopic fork front suspension, and plunger-link spring rear suspension. The front and rear brakes were drum brakes, and the wheels were made of steel with laced wire spokes. The dimensions were length 2100 mm / 82 in and wheelbase 1422 mm / 56 in. The dry weight was 211 kg / 465 lbs for the 4G, 197 kg / 435 lbs for the Mark I, and 193 kg / 425 lbs for the Mark II. The fuel capacity was 23 L / 6.0 US gal, and the top speeds were 141 km/h / 87 mph for the 4G, 145 km/h / 90 mph for the Mark I, and 160 km/h / 100 mph for the Mark II.

Technical specifications:

Make Model: Ariel Square Four 4G 1000, Mark I, Mark II

Year: 4G: 1936 – 48 Mk I: 1949 – 53 Mk II: 1953 – 58


Production: 4G: 4 288 Mk I: 3 922 Mk II: 3 828
Engine: Four stroke, vertical square four, OHV, 8 valves
Capacity: 997 cc / 60.8 cu in
Bore x Stroke: 65 x 78 mm
Cooling System: Air cooled
Compression Ratio: 6.0:1
Exhaust: Mk I, Mk II: 2 x 2-into-1
Induction: SU carburetor
Starting: Kick start
Max Power: F4 G, Mk I: 26 kW / 35 hp @ 5500 rpm Mk II: 34 kW / 45 hp @ 5500 rpm
Transmission: 4-Speed
Final Drive: Chain
Frame: Single down tube
Front Suspension: Telescopic fork
Rear Suspension: Plunger-link spring

Front Brakes: Drum
Rear Brakes: Drum
Wheels: Steel, laced wire spokes
Dimensions: Length: 2100 mm / 82 in
Wheelbase: 1422 mm / 56 in
Dry Weight: 4G: 211 kg / 465 lbs Mk I: 197 kg / 435 lbs Mk II: 193 lg: 425 lbs
Fuel Capacity: 23 L / 6.0 US gal
Top Speed: 4G: 141 km/h / 87 mph Mk I: 145 km/h / 90 mph Mk II: 160 km/h / 100 mph

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