Motorcycle: Sportsters - The First Twins
Date: Sunday, October 31 @ 22:56:37 UTC
Topic: Motorcycle, Motorcycles, Motor Cycle
The First Twins
From a modem perspective, the expressions "Harley-Davidson" and "V-twin" are practically synonymous, yet it was not always so. Expanding the Harley range from singles to twins was a logical progression as Harley attempted to broaden its share in the rapidly expanding American market. The first American V-twin was the 695cc Curtiss of 1903 and Harley's first prototype was built three years later, making its first public appearance at the Chicago motorcycle show in 1907.
Exactly two years later, the Model 5-D twin was offered for sale, with the 45-degree configuration that is now a Harley hallmark. In almost every other respect, however, the engine was entirely different. As with the contemporary singles on which it was based, the F-head valve layout was inlet-over-exhaust, with the inlets of the "automatic" type, in which the valve was simply "sucked" open by the falling piston rather than being moved mechanically by a cam. After almost two decades of painstaking evolution, the F-head layout culminated in the legendary JH and JDH twin-cam models, the "superbike" race replica machines of their day.
As the 1920s drew to a close, side-valve engines became the Milwaukee norm, heralding an era dominated by flatheads such as the enduring "45" and the mammoth 80-inch VL - machines that put the muscle into Milwaukee.
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