SPECIFICATION. ENGINE.
Bore 86.4 m.m. Stroke 95 m.m. Capacity 557 c.cs. Detachable cylinder head. Double roller bearing big end. Ball bearings on both sides of main shaft. Aluminium alloy piston. Ground timing gears. Engine shaft shock absorber. Dry sump lubrication as described below.

Courtesy Howard Burrows

Ariel Motorcycles of the 1930s