Does the bike have any modifications to the engine or exhaust?
Could you have filled up with gas with too low an octane rating? Not a problem in most countries.
When I first got my CB500F I shifted gears to run the engine around 3000 rpm. I found the engine was not happy accelerating from 3000 rpm, though it would do it. Now I ride around 4000 rpm (or higher) and the engine is happy.
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.