BIG-HEARTED BEEZER
It’s a situation familiar to many motorcycle wrenchers: In one corner of the garage is a frame left over from a previous project, and hiding under the proverbial workbench is a similarly orphaned engine.
In Lyle Whitter’s case, the engine was a 1949 alloy two-pipe Ariel Square Four Mk1, and the frame was a 1957 BSA A10 Golden Flash. And the question uppermost in Whitter’s mind: would the two go together?
The eventual answer was … yes — but not without some considerable workshop skill and patience.
The engine
The engine that Whitter used for his BSA-framed custom bore little resemblance to Edward Turner’s original design — except for the “Square Four” cylinder layout.
In the 1920s, Turner owned a motorcycle dealership, but his goal was to become a designer for one of the big British motorcycle makers. His calling card was an elegant and innovative design for a 500cc 4-cylinder motorcycle engine. Only Ariel showed any serious interest, offering Turner a job in the engineering and design office working under Valentine Page.
Turner conceived a unit-construction powerplant with two crankshafts of 61mm stroke coupled by central bevel gears, the rear crankshaft also driving the integral 3-speed transmission. Each crankshaft ran on two main bearings inboard of the flywheels with “overhung”
