How the Harley-Davidson Knucklehead Defined the American V-Twin Sound

In 1936, Harley-Davidson bet its future on an engine nobody had asked for. The country was still climbing out of the worst motorcycle sales slump in American history, and the company’s big twins were still running on decades-old flathead technology. Into that uncertain moment, Harley introduced the 61 OHV, complete with a new frame, a new fork and an entirely new overhead-valve V-twin. Nobody called it the Knucklehead yet. That name was still a decade away. What riders got, whether they realized it or not, was the engine that would define what a Harley-Davidson sounds like to this day.

Why Harley Needed a New Engine

By 1933, the US motorcycle market had fallen to its lowest point on record, and it stayed there for years. Harley-Davidson and its longtime rival Indian were fighting over a shrinking pool of buyers, and neither company had much room for a costly misstep. Harley’s big twins ran on flathead engines, a side-valve design with total-loss oiling that let oil burn off or drip onto the road instead of recirculating through the engine.