You are responsible for your passenger. Plain and simple. You had better have insurance if you're taking passengers, otherwise, you could be held legally liable for all damages and medical bills that arise. You are on very dangerous ground taking passengers without insurance. At least get insurance and make them wear gear and make them sign a waiver. I don't know if the waiver will hold any water in court, but it will at least show that the passenger was aware of the dangers and chose to ride in spite of them.