The speed of any motorcycle, regardless of displacement, is controled by the right hand of the rider. It is easy to say that a new rider should start off on smaller bikes, but the bottem line is that it is the rider and their experience that controls the speed and actions of the motorcycle in opperation. I think that if a person is approraitly cautious and gets a proper grounding in motorcycle operation through a MSF class should be able to handle a 600cc sport bike with no problem.