Engine heating on CB550

Hi, 

I am working on 1974 cb550, i am seeing there is lot of heat coming from engine 1 and 2 and also from the exhaust connecting to these two engines within a couple of minutes of idle run. I cleaned the carbs, changed the spark plugs, got new engine oil, checked the timing, and also adjusted the air screw as per the guide and youtube videos. Not sure what is going on with it. Need suggestions on what needs to be checked.