Yeah, that does sound like an air leak, it wont rev up because it isn't getting enough fuel. Is the rubber boot between the reed and the carb ripped? Sometimes the tear in invisible but can cause this. Also, is the gasket to the reed cage and the engine block in good shape and seated correctly?
I would say it also sounds like a carb problem, but you cleaned it all out. If the floats are set to factory settings, I wouldn't set them to dump more fuel, as you may end up making it piss gas out the overflow. But, have you cleaned the float jet hole where the fuel actually flows into the carb from? Sometimes that is that culprit. If you can easily blow air through it than your all set there. If not, that clean that part out. It sounds like the bike is being is starved of fuel by either an air leak or insufficient fuel flow in the carb.