have a signed bill of sale but can buyer still sue me?

My boyfriend and I sold a used 2006 Kawasaki Vulcan motorcycle. It was listed on both craigs list and a motorcycle site that he frequents. We sold it to a man out of Phoenix but after purchase he decided he wasn't happy and started to harass us via phone and text. I filed a police report and it has helped stop the texts but if he sues would he have a case? He said we had a misleading ad but he signed a b.o.s that I specifically wrote sold "As Is" No warranty or guaranty. He was not happy that I would not let him have our License plate - which is the law to take off in the state of colorado. Then he said the ad stated there was a part included with the bike (which is not included and since I did not complete the ad's my boyfriend did, I'm not 100% sure if it did or did not) he is demanding we pay for half this part-we told him no sorry. It was our understanding it was on the bike and since we didn't have issues assumed all was fine. I'm worried now- not only about a suit but our safety