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 Protection Agency conducted emissions-certification and representative emissions test in Ann Arbor, Michigan, in 2005. Subsequently, Harley-Davidson produced an "environmental warranty". The warranty ensures each owner that the vehicle is designed and built free of any defects in materials and workmanship that would cause the vehicle to not meet EPA standards. In 2005, the EPA and the Pennsylvania Department of Environmental Protection (PADEP) confirmed Harley-Davidson to be the first corporation to voluntarily enroll in the One Clean-Up Program. This program is designed for the clean-up of the affected soil and groundwater at the former York Naval Ordnance Plant. The program is