Harley-Davidson models. In the late summer of 1929, Harley-Davidson introduced its 45 cubic inches (737 cm³) flathead V-Twin to compete with the Indian 101 Scout and the Excelsior Super X. This was the "D" model, produced from 1929 to 1931. Riders of Indian motorcycles derisively referred to this model as the "three cylinder Harley" because the generator was upright and parallel to the front cylinder. The Great Depression began a few months after the introduction of their 45 cubic inch (737 cm³) model. Harley-Davidson's sales fell from 21,000 in 1929 to 3,703 in 1933. Despite this, Harley-Davidson unveiled a new lineup
Harley-Davidson operated intake valves, as opposed to the "automatic" intake valves used on earlier V-Twins that opened by engine vacuum. With a displacement of 49.48 cubic inches (811 cm³), the 1911 V-Twin was smaller than earlier twins, but gave better performance. After 1913 the majority of bikes produced by Harley-Davidson would be V-Twin models. In 1912, Harley-Davidson introduced their patented "Ful-Floteing Seat", which was suspended by a coil spring inside the seat tube. The spring tension could be adjusted to suit the rider's weight. More than of travel was available. Harley-Davidson would use seats of this type until 1958. By 1913,