I am having a similar problem with my vf750s. Around 5,000 rpm it hesitates almost like it is not receiving enough fuel or air or something. The problem began (from what I remember) after my bike fell over being backed out of the driveway. It has not resolved itself after putting different carb cleaners through the fuel system. I am thinking about taking off the carbs and cleaning them out, but as you know that is a big job on this bike and I will probably damage parts.