Kawasaki Forums - 2006 ninja 250 stalling problem

Sorry if this is in the wrong discussion room but I couldn't find a mechanical help forum. I let my bike sit during the winter this past year and don't have a garage so unfortunately it weathered the storm, rain or shine. Now it's bike season I can't seem to fix the problem. It starts fine. It only idles if I turn the idle adjustment to the highest but it's not idling rough at all.

The problem is that when I try and give it any gas it only gets up to about 3k rpm before bogging down and dying out. I've taken the carbs apart and cleaned them, I've adjusted the air/fuel ratio screw and still nothing.

In the beginning it used to do this but sometimes would let me rev it all the way, but once I try taking off once it seemed fine it wouldn't go anywhere and just stalled out again. It hasn't been able to go over 3k rpm since I've messed with the jets but I really have no clue what it could be. I've replaced then cdi box and still no luck. Any suggestions at all? The spark plugs are black but from the research I've been doing it seems that it's not getting enough air?? Any suggestions will be greatly appreciated. I just wanna get back on the road before I miss the entire bike season!