First, take a motorcycle safety class by MSF. It will teach you a ton and may save your life, and you get to ride little Honda Rebels. I always recommend the Kawasaki Ninja 250 to everyone as a beginner bike because they're fun, cheap, readily available and you won't tire of it after after the first season. The smallest Yamaha sport bike is a 600. There are smaller V Star crusers like the 250 but it's air cooled and won't be able to withstand sustained speeds of over 70 without issues. The 650 is good. What do I know? I ride a Honda Shadow and have only owned 1 Yamaha, my favorite a 650 Special II, still miss it.
