Back to Bike FinderYears: 1953 · 1952 · 1951 · 1950 · 1949
Ariel MK1 Square Four
1949Allround

Ariel MK1 Square Four

Key specifications

Engine
997 cc
Power
40 HP
Weight
193 kg
Fuel type
petrol
Fuel capacity
6.1 L
Front brakes
Expanding brake (drum brake)
Rear brakes
Expanding brake (drum brake)

Overview

Introducing the 1949 Ariel MK1 Square Four, a motorcycle that embodies the spirit of post-war innovation and craftsmanship. As part of Ariel’s celebrated lineup, the MK1 Square Four carved out its niche in the allround category, appealing to riders who sought a blend of performance, comfort, and classic style. With its robust design and sophisticated engineering, this motorcycle quickly gained a dedicated following among enthusiasts who appreciated its unique features and powerful presence on the road. At the heart of the Ariel MK1 Square Four is an impressive 997 cc single-cylinder four-stroke engine that delivers a spirited 40 horsepower at 5800 RPM. This power, combined with its lightweight frame, results in a delightful riding experience that balances speed and agility. Riders will appreciate the smooth acceleration and steady handling, thanks in part to the air-cooled engine and efficient carburettor fuel system. Whether navigating winding country roads or cruising through city streets, the MK1 Square Four offers a thrilling ride that captures the essence of motorcycling freedom. The MK1 Square Four boasts several standout features that showcase Ariel's engineering prowess. Its tubular single-loop frame provides exceptional rigidity while keeping the weight down to a manageable 193 kg (425.5 lbs), ensuring nimble maneuverability. The motorcycle is equipped with expanding drum brakes at both the front and rear, measuring 178 mm and 203 mm, respectively, providing reliable stopping power. With a fuel capacity of 23 liters (6.08 gallons), riders can embark on longer journeys without the frequent need to refuel, all while enjoying the undeniable charm of its classic design, which features elegant lines and a distinctive silhouette. **

Pros

  • Performance: The 997 cc engine offers a lively power output, delivering a thrilling ride that is both responsive and enjoyable.
  • Comfort: Designed for versatility, the MK1 Square Four is comfortable for both short commutes and long-distance rides, making it a great allround motorcycle.
  • Classic Appeal: Its timeless design and unique engineering make it an eye-catching choice for vintage motorcycle enthusiasts.

Cons

  • Weight: At 193 kg, it may be heavier than some competitors in the allround category, which could affect handling for novice riders.
  • Braking System: While the drum brakes are reliable, they may not provide the same stopping power as modern disc brakes, particularly in emergency situations.
  • Maintenance: As with many vintage motorcycles, sourcing parts and maintaining the MK1 Square Four can pose challenges, requiring dedicated care from its owner.

Technical details

Source specification data

Make
Ariel
Model
MK1 Square Four
Category
Allround
Power
40.00 HP (29.2 kW)) @ 5800 RPM
Fuel System
Carburettor
Displacement
997.00 ccm (60.84 cubic inches)
Cooling System
Air
Engine Details
Single cylinder, four-stroke
Transmission Type Final Drive
Chain
Dry Weight
193.0 kg (425.5 pounds)
Fuel Capacity
23.00 litres (6.08 gallons)
Overall Length
2,100 mm (82.7 inches)
Power Weight Ratio
0.2073 HP/kg
Seat
Dual
Wheels
Spoked
Rear Tyre
4-18
Frame Type
Tubular single loop
Front Tyre
3.25-19
Rear Brakes
Expanding brake (drum brake)
Front Brakes
Expanding brake (drum brake)
Rear Brakes Diameter
203 mm (8.0 inches)
Front Brakes Diameter
178 mm (7.0 inches)