When Chief Designer Phil Walker started work on a parallel twin for Britain’s Associated Motor Cycles, he seemed determined to better the competition.
By 1949, every major British motorcycle manufacturer had announced a parallel twin, including BSA, Ariel, Norton and Royal Enfield. (Velocette and Vincent, as usual, went their own way.) Edward Turner’s Big Idea had become ubiquitous in the industry, and represented modern thinking and sporting performance. Suddenly, singles and V-twins looked stodgy and dated.
Compared with a single-cylinder 4-stroke of the same capacity, power delivery was smoother, thanks to twice the power strokes for the same revs. That also allowed for lighter flywheels, so pickup was faster. Compared with a V-twin, parallel twins were more compact and typically lighter, too.
Stylishly late
Associated Motor Cycles (AMC), AJS and…