Yes, Harley-Davidson has produced 4-cylinder motorcycles in its history. One notable example is the Harley-Davidson VR1000, which was a high-performance sportbike produced from 1994 to 2001. The VR1000 was designed for competition in the Superbike World Championship and featured a liquid-cooled 996cc V4 engine. The VR1000 incorporated advanced technology for its time, including fuel injection, overhead cams, and four valves per cylinder.
Although the VR1000 was not as successful in racing as Harley-Davidson had hoped, it marked an important milestone for the company as their first foray into the world of 4-cylinder motorcycles. The VR1000 models are relatively rare and sought after by collectors.
It's worth noting that while the VR1000 was Harley-Davidson's most prominent 4-cylinder motorcycle, there have been a few other instances of prototype or concept bikes with 4-cylinder engines in Harley-Davidson's history. However, these prototypes were not mass-produced or brought to market.