Dock66 Motorcycle Parts offers gas caps in different styles and versions ? with bajonett and thread close. The gas caps match Dock66 gas tanks, custom motorcycles and Harley-Davidson® motorcycles from 1936. Tipp for H-D riders with stock gas tank: The company developed four different types. 1. bajonett 1936-72, 2. bajonett 1973-82, 3. thread 1982-95, 4. thread 1996 and up.