Rear brake seals and Tight Valves

[humbucker88]

I've double checked, all valves are in spec apart from one intake valve on cylinder 3. The bike is burning coolant and pressure from cylinder 3 is getting into the cooling system. The spark plug on cylinder 3 was also rusted, it's carb was coated in oil on the outside, and the float chamber had brown powder on the inside but nothing is rusted. I've replaced the head gasket and cleaned the carbs, if the bike still burns coolant I'm assuming I need a new head?