Back to Bike FinderYears: 1959 · 1958 · 1957 · 1956 · 1955 · 1954 · 1953
Ariel 4G Square Four Mark II
1956Allround

Ariel 4G Square Four Mark II

Key specifications

Engine
995 cc
Power
45 HP
Weight
193 kg
Fuel type
petrol
Fuel capacity
4.2 L
Transmission
4-speed
Front brakes
Expanding brake (drum brake)
Rear brakes
Expanding brake (drum brake)

Overview

The 1956 Ariel 4G Square Four Mark II, affectionately known as the "Squariel," stands as a remarkable testament to the engineering prowess of mid-20th century motorcycling. Launched by the British motorcycle manufacturer Ariel, this model epitomizes the allround category, blending performance, style, and innovative technology into a single, iconic machine. Designed by the legendary Edward Turner, the Square Four Mark II was aimed at riders seeking a capable, versatile motorcycle that could handle both city commutes and long-distance touring with ease. With its striking red and chrome design, it not only delivers in function but also makes a bold aesthetic statement on the road. At the heart of the 4G Square Four Mark II lies its distinctive square four-cylinder engine, boasting a displacement of 995 ccm and generating a robust 45 horsepower at 5,500 RPM. This unique configuration not only enhances the bike's performance capabilities but also delivers an exhilarating riding experience. With a top speed of 160 km/h (99.4 mph), riders can expect spirited acceleration that makes overtaking and highway cruising a pleasure. The 4-speed gearbox paired with a chain final drive ensures smooth power delivery, while the air-cooled design keeps the engine running efficiently, even on warm summer days. The low compression ratio of 6.0:1 strikes a balance between performance and reliability, making it suitable for a variety of riding conditions. The engineering innovations of the Mark II extend beyond its engine. One of its standout features is the re-designed cylinder head with separate barrels, allowing for four distinct exhaust pipes that contribute to a unique sound signature. The full cradle frame provides excellent stability and handling, complemented by an oil-damped telescopic front fork and a plunger-link rear suspension that offers a comfortable ride over rough terrain. The braking system, featuring expanding drum brakes front and rear, ensures adequate stopping power, while the generous fuel capacity of 16 liters (4.23 gallons) means fewer stops at the pump for longer journeys. With thoughtful design elements like a kick starter and a ground clearance of 140 mm, the 4G Square Four Mark II embodies both practicality and flair. In summary, the 1956 Ariel 4G Square Four Mark II is a classic motorcycle that combines unique engineering, solid performance, and timeless design. It remains a beloved choice among vintage motorcycle enthusiasts who appreciate its character and capabilities on the open road.

Pros

  • Unique Engine Design: The square four-cylinder configuration offers a distinctive performance profile and sound that stands out in the motorcycle market.
  • Comfortable Ride: The combination of a well-designed suspension system and an ergonomic frame provides a smooth and enjoyable riding experience.
  • Versatile Performance: With its capable engine and solid brakes, the Mark II is adept at handling both urban commuting and extended touring.

Cons

  • Weight: At 193 kg (425.5 pounds), the bike may feel a bit cumbersome for newer riders or those looking for a more nimble motorcycle.
  • Drum Brakes: While effective, the drum brake system may not offer the same level of stopping power and responsiveness as modern disc brakes.
  • Kick Starter: The traditional kick starter may be less convenient for riders accustomed to electric start systems, especially in challenging conditions.

Technical details

Source specification data

Make
Ariel
Model
4G Square Four Mark II
Category
Allround
Light
7.5 inch, 30 Watt headlamp.
Starter
Kick
Comments
Also
called ´
Squariel
´.
Designed
by
Edward Turner
.
I
has separate barrels, a re-designed cylinder head with four separate exhaust pipes from two cast-aluminium manifolds and a rocker-box combined with the inlet manifold.
Color Options
Red/chrome
Power
45.00 HP (32.8 kW)) @ 5500 RPM
Gearbox
4-speed
Top Speed
160.0 km/h (99.4 mph)
Engine Type
Double twin cylinder arranged as a square.
Fuel System
Carburettor
.
C2
carburettor with air cleaner
Bore X Stroke
65.0 x 78.0 mm (2.6 x 3.1 inches)
Compression
6.0:1
Displacement
995.00 ccm (60.71 cubic inches)
Cooling System
Air
Engine Details
Square four cylinder
Lubrication System
Dry sump with dual oil pump.
Valves Per Cylinder
2
Transmission Type Final Drive
Chain
Dry Weight
193.0 kg (425.5 pounds)
Oil Capacity
3.40 litres (0.22 quarts)
Fuel Capacity
16.00 litres (4.23 gallons)
Overall Width
686 mm (27.0 inches)
Overall Length
2,184 mm (86.0 inches)
Ground Clearance
140 mm (5.5 inches)
Power Weight Ratio
0.2332 HP/kg
Wheels
Wire spoked. Dunlop tyres.
Rear Tyre
4.00-18
Frame Type
Full cradle
Front Tyre
3.25-19
Rear Brakes
Expanding brake (drum brake)
Front Brakes
Expanding brake (drum brake)
Rear Suspension
Plunger-link spring
Front Suspension
Oil damped telescopic fork
Rear Brakes Diameter
203 mm (8.0 inches)
Front Brakes Diameter
178 mm (7.0 inches)

Available colors

Red/chrome