Four-Cylinder

1939 Ariel Square Four 1939 ARIEL SQUARE FOUR BACKGROUND The original Square Four was conceived by legendary motorcycle designer, Edward Turner, who later created the game-changing Triumph parallel twin. His original design for the Square Four was an OHC (Overhead Cam) design with a displacement of 500cc when it debuted in 1931. However, constant overheating …

1957 Ariel Square Four 1957 ARIEL SQUARE FOUR – GETTING LONG IN THE TOOTH Alas, the world was changing, and with it the motorcycle market. The Ariel Square 4 designed decades before, was keyed to another age, one where acceleration and all-out top speed weren’t as important as smoothness and reliability. Hence the Square Four …

1950 Ariel Square Four 1950 ARIEL SQUARE FOUR BACKGROUND The original Ariel Square Four was created by legendary engine designer, Edward Turner in 1930. In its original form, it displaced 500cc and had four cylinders arranged in a ‘square’. It was unusual in that it had two crankshafts, one behind the other, each with two …

1948 Ariel Square Four 1948 ARIEL SQUARE FOUR BACKGROUND The Ariel Square Four engine was originally designed in 1928 by Edward Turner, the man who later came up with the vertical twin for Triumph. In original form, it started out as a 500cc and was quickly expanded to 601cc. The Square Four was essentially two …

1956 Ariel Square Four 1956 ARIEL SQUARE FOUR – NEW & IMPROVED The Square Four went through a major revision in 1953, with a new cylinder head and manifolds, prompting a new sub-model designation, Mark II, which ran from 1953 through Ariel’s final year, 1959. Prior to 1953, both cylinders on each side shared just …

1959 Ariel Square Four 1959 ARIEL SQUARE FOUR- IT’S FINAL YEAR Alas, the world was changing, and with it the motorcycle market. The Ariel Square Four designed decades before, was keyed to another age, one where acceleration and all-out top speed weren’t as important as smoothness and reliability. Hence the Square Four engine was built …

1953 Ariel Square Four 1953 ARIEL SQUARE FOUR BACKGROUND The original Ariel Square Four was created by legendary engine designer, Edward Turner in 1930. In its original form, it displaced 500cc and had four cylinders arranged in a ‘square’. It was unusual in that it had two crankshafts, one behind the other, each with two …

1955 Ariel Square Four 1955 ARIEL SQUARE FOUR – NEW & IMPROVED The Square Four went through a major revision in 1953, with a new cylinder head and manifolds, prompting a new sub-model designation, Mark II, which ran from 1953 through Ariel’s final year, 1959. Prior to 1953, both cylinders on each side shared just …

1951 Ariel Square Four 1951 ARIEL SQUARE FOUR BACKGROUND The original Ariel Square Four was created by legendary engine designer, Edward Turner in 1930. In its original form, it displaced 500cc and had four cylinders arranged in a ‘square’. It was unusual in that it had two crankshafts, one behind the other, each with two …

1932 Aerial Square Four 1932 ARIEL SQUARE FOUR GROWS TO 600cc The first production Ariel Square Four was the 1931 Model 4F and it displaced 500cc. For the 1932 model year, the bore was increased by 5mm, pushing displacement up to 601cc to accommodate the growing sidecar market in the UK. In its new form, …

1958 Ariel Square Four 1958 ARIEL SQUARE FOUR – GETTING LONG IN THE TOOTH Alas, the world was changing, and with it the motorcycle market. The Ariel Square 4 designed decades before, was keyed to another age, one where acceleration and all-out top speed weren’t as important as smoothness and reliability. Hence the Square Four …

1952 Ariel Square Four 1952 ARIEL SQUARE FOUR BACKGROUND The original Ariel Square Four was created by legendary engine designer, Edward Turner in 1930. In its original form, it displaced 500cc and had four cylinders arranged in a ‘square’. It was unusual in that it had two crankshafts, one behind the other, each with two …