Harley-Davidson motorcycles typically use halogen bulbs for their headlights and turn signals. Halogen bulbs are commonly used in many motorcycles and automobiles due to their brightness, longevity, and affordability. However, it's worth noting that Harley-Davidson has produced a wide range of motorcycle models over the years, and different models may have different lighting setups. It's always a good idea to consult the specific owner's manual or contact a Harley-Davidson dealership for accurate and up-to-date information on the bulb types used in a particular model.