Harley-Davidson® DL Model

As automobiles became the preferred option for day-to-day transportation, motorcycle sales suffered. In response, Harley-Davidson heavily promoted motorcycling as a "pleasure and sporting" activity. To make the bikes more appealing, the company experimented with muscular engine types, including an inline four cylinder and a 90 cubic inch shaft drive. In the end, the winner was the 45 cubic inch, side-valve Flathead engine that powered the Model DL. It holds the distinction as the longest-lived engine in Harley-Davidson history.