The fuel consumption of a Harley-Davidson motorcycle can vary depending on several factors, including the specific model, engine size, riding conditions, and individual riding style. On average, Harley-Davidson motorcycles typically have a fuel efficiency range of around 35-45 miles per gallon (mpg) or approximately 14.9-19.1 kilometers per liter (km/l). However, it's important to note that this is a rough estimate, and the actual fuel economy may differ based on the factors mentioned above. It's always a good idea to consult the specific model's specifications or owner's manual for more precise information.