sticky throttle cable + rough road? try rev'ing engine in that rpm range with bike stopped and in neutral, see how smooth throttle response is.
frozen link in chain? I expect this would affect 4800-5400 rpm only in a single gear.
2014 CB500F: GSXR600 rear shock, Traxxion fork emulators+springs, Kuryakyn Throttle Boss, IDEA Gear Indicator, Slipstreamer S-06 windscreen, SW-Motech handlebar risers, LED tail light, rubber tank side pads.