Carburetor Problems? 1981 KZ440

I have a 1981 KZ440 which ran great last year but now will only idle good, well fair, not really good but will not rev up at all. It will rev up if I gently give it a little more throttle. It will only rev up so much then it will stall. This is all just sitting in my garage, wouldn't dare try to ride it like this. Also when I do try and rev it up the engine makes a loud knocking sound. I think this might be in the carburetors but I wanted to see if anyone had any thoughts on this problem as I am not very familiar with these bikes. It has electronic ignition, good spark, thats about all I know so far.

Clean the carbs and fuel system and all will probably be good.

Thats what I figured. I will just do that now. Won't hurt anything anyways.