Yes, Harley-Davidson has produced motorcycles with four-cylinder engines in the past. One notable example is the Harley-Davidson VR1000, which was a sportbike designed for racing in the Superbike World Championship. The VR1000 was introduced in the early 1990s and featured a liquid-cooled 996cc V-twin engine with four valves per cylinder. However, the VR1000 project was discontinued in 2001, and Harley-Davidson has primarily focused on producing motorcycles with their signature V-twin engines since then.