The specific amount of oil required for a Harley-Davidson motorcycle can vary depending on the model and year. Generally, most Harley-Davidson Big Twin models, such as the Harley-Davidson Softail, Dyna, and Touring motorcycles, have an oil capacity of approximately 4 to 5 quarts (3.8 to 4.7 liters). It's always recommended to consult the owner's manual or service manual for your specific Harley-Davidson model to get the accurate oil capacity information. Additionally, it's important to follow the manufacturer's recommendations regarding oil type and viscosity for optimal performance and to ensure proper maintenance of your motorcycle.