Cylinder not firing under 2 to 3000rpm

Having some trouble with my ZX6 01. Cylinder 4 is not firing bellow 2 to 3000rpm, once it gets above that is goes unreal.

I have checked spark plugs, electrics, valve clearance, engine compression, carby looks ok.

Anyone have any ideas what I can look for? Much appreciated.

Sounds like the idle circuit is blocked. I would take the carbs out and remove the idle jet (you take the float bowl off for this) and give it a good clean out (soak it in carby cleaner and poke at the inside with the finest nylon fishing line you can get your hands on) and if that doesn't help then clean the fuel's path inside the carby out. Which entails removing the idle adjustment screw (the one that is usually 1.5ish turns out) and its spring/o ring and give it a good cleanout once you have taken all the all rubber peices off as carby cleaner can destroy them.