The Early Single-Cylinder gasoline engine was underpowered and inefficient, though Harley’s singles were among the best available. The “atmospheric” inlet valve relied on a light spring to keep it closed and was forced open by the pressure created from the falling piston. The system was simple, but it couldn’t work properly at anything other than slow engine speeds. Increasing capacity boosted the power output, but it was no substitute for improved efficiency.
The Наrley single was just a good solid dependable motorcycle at a time when most of them were not.
Richard Rosenthal (Motorcycle Historian)
Rugged and dependable
In an era of unreliable and uncomfortable motorcycles, the Harley single stood out as a solid workhorse capable of covering long distances. The well-made engine got some of the credit, but Harley’s sprung seat-post was a welcome feature for the often appalling road conditions.
The Competition. 1911 EXCELSIOR MODEL K
The Chicago Excelsior company was the third-biggest motorcycle manufacturer in the US until its closure in 1931. Like the Harley, this machine had belt-drive, but used the engine cases as part of the frame, as opposed to Harley s loop-frame system.
Single with Bosch magneto
A magneto was introduced as an option in 1909. This simple electric generator provided a spark for the ignition system and made the early Harley a more useable machine.
No female frills
Some European manufacturers offered “ladies’ models” with special frames and skirt-guards. Harley women didn’t need these luxuries.
The inlet valve was kept closed with the exposed spring on the top of the cylinder. As the piston fell, it created a vacuum in the cylinder, resulting in the valve being forced open by atmospheric pressure. A charge of fuel and air mix was then sucked in through the carburetor.