I think most people CAN ride. Here are some things, in no particular order that I’ve seen over the years that might “preclude” people from being safe riders:
1) Right mental attitude, which includes accepting and managing risk, understanding their respective personal limits, and accepting 100% responsiblity for everything that happens to them on a motorcycle. It sounds funny, but you will be safest on a motorcycle when believe that everything that occurs when you’re riding is YOUR responsibility. Otherwise, you’re toast.
2) Situational awareness. Part of this is described above, but there are a lot of things that are happening when you ride a motorcycle, and you need to be aware of all of them. Many people struggle with this..they can’t seem to process all of the information that they are revieving as they ride (or drive) and get into trouble because of this. If you know someone who has a lot of car accidents, whether it’s their fault or not, they might not be good candidates for motorcycling.
3) Coordination. Lack of coordination alone shouldn’t preclude someone from taking the class and learning, but the skills needed to safely operate a motorcycle are perishable. If you don’t right often enough, and you don’t practice ALL of your skills, EACH time you ride, then you’re going to get in trouble. If you lack the coordination neccesary to manipulate all of the controls, you’re going to have problems. Not everyone can dribble a basketball or play ping pong. Having said that, everyone SHOULD be able to learn, but then those who struggle the most must practice the most.
I can think of few physical limitations (legal blindness, paraplegics, quadraplegics) that would preclude a person from riding. I know of people with missing limbs for instance that ride, and I know of one who won a national flat track championship…with one arm!
Hope that helps…