To answer this question, it's not going to be hard. You can get a motorcycle from several places actually, from survivor camps to gas stations and roads. Basically, you can loot your way to a motorcycle, but you can also buy spare parts. If you are well on the money part, however, you can buy the whole motorcycle without having to make it from scrap. By visiting the in-game store you can purchase a fully functional motorcycle for 5000 coins.