Harley-Davidson Model 5-D
Harley-Davidson's first production V-twin arrived in 1909, adding a second cylinder to make more power—but also teaching the young company hard lessons about reliability.
1909 Harley-Davidson Model 5-D at the Harley-Davidson Museum · Michael Barera · CC BY-SA 4.0
More than a set of wheels.
Only 27 Model 5-D motorcycles were built in 1909. This page follows that first 45-degree V-twin with automatic intake valves, not the improved mechanically operated V-twins that followed after a one-year pause.
Look a little closer.
Its uneven 315-degree and 405-degree firing gaps helped create the loping rhythm people later associated with Harley V-twins.
Photos show an example of the model or generation. The pictured vehicle’s year, equipment, or modifications can differ from the specification described here.
A bold first try that needed a rethink
The 5-D roughly doubled the company's single-cylinder power, but its automatic intake valves and direct belt drive were difficult to start and control. Harley-Davidson withdrew the design after 1909 and returned with a much better V-twin in 1911.
Source: Harley-Davidson · Engine types through history ↗The 45-degree idea stayed
Although the first engine was short-lived, its narrow V angle made the twin fit a bicycle-like frame. Later Harley engines kept the basic 45-degree arrangement while replacing the troublesome valve and drive details.
Source: Harley-Davidson Insurance · Motorcycles that changed Harley-Davidson ↗Where these facts come from
- Harley-Davidson · Engine types through history
- Harley-Davidson Insurance · Motorcycles that changed Harley-Davidson
- Harley Clásica · 1909 Model 5 technical history
Selected facts checked for this edition. Some source pages link to broader model families. Last reviewed September 30, 2026.