If you have any assets - money in bank, house, etc. - if you are going to sell something like motorized bicycles you built you need a good lawyer on the string and good insurance. If you are successful, you will be sued. Tort claims are not about right or wrong or fair. Tort claims are about a lawyer being able to convice a jury of people the lawyer picks that the injured dude is a sad case and really should get some free money; or can convince the insurance company that it would be cheaper for them to settle out-of-court than defend in court. I worked for a power utility once. Two guys got drunk, stole a long chain from a parked 18-wheeler, took their 4x4, pulled down the fence plastered with DANGER HIGH VOLTAGE KEEP OUT signs at one of the electrical substations, and heaved the chain over the buss work in the station to cause a fault and shut off the power. It worked, except one of them was fried dead. The families sued the utility and got several million. In America, there is NO SUCH THING as 'not liable.' Talk to a lawyer and get good insurance.