Yes, Harley-Davidson motorcycles do require oil in the crankcase. The crankcase is an integral part of the engine and houses the crankshaft, connecting rods, and other components. Oil is necessary to lubricate these moving parts and to reduce friction, heat, and wear within the engine. Proper lubrication is essential for the smooth operation and longevity of the engine.
Harley-Davidson motorcycles typically use a V-twin engine design, and like most internal combustion engines, they require regular oil changes and maintenance to ensure optimal performance and reliability. It's important to follow the manufacturer's guidelines regarding oil type, viscosity, and change intervals to maintain the engine's health and performance.