United States · U.S. first-production V-twin · one-year 1909 model

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.

Motorcycle pioneers

Exact museum-labeled 1909 Model 5-D; the crop emphasizes it but a small part of the adjacent 1906 Model 2 remains visible.

Left-side museum display · Photo shows Exact museum-labeled 1909 Model 5-D; the crop emphasizes it but a small part of the adjacent 1906 Model 2 remains visible..
1909 Harley-Davidson Model 5-D at the Harley-Davidson Museum · Michael Barera · CC BY-SA 4.0

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A place in vehicle history

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

Selected facts checked for this edition. Some source pages link to broader model families. Last reviewed September 30, 2026.

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