Can you return a private party sale motorcycle?

I bought a Motorcycle through a private sale 2 days ago. I was informed the bike ran, and only needed a battery. The bike started that day. I went to pick it up yesterday, and the bike would not run, even on a battery charger, which tells me there is something else wrong with the motorcycle. I have not registered the bike, I never signed the title, and I never took the motorcycle from the man's home that I sold it to. I am trying to return it but he refuses to give me my money back. What legal recourse do I have if any?