Though the Harley-Davison X9A's 4.3 horsepower doesn't sound like much, it represented a lot of muscle for 1912.

1912 Harley-Davidson X8A Pictures

While many companies had gone to a mechanical intake valve by this time, the 1912 Harley-Davidson X8A motorcycle stuck with an atmospheric intake valve.

A tall lever on the left side of the tank activated the "Free Wheel Control," Harley's early clutch system.

The atmospheric intake valve was located beneath the small dome at the top of the engine's right side.

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