If there are no leaks and that's a big IF, it just sounds like the mixture is too lean and yes that will cause overheating. Richen both the high speed needle and low speed needle about half a turn and fly again. If this cures the problem then reset both needles to their optimum slightly rich settings and you should be all set. If the above doesn't work the you need to clean the engine and fuel system and check for leaks or blockages everywhere. When an engine and plane have not been used in a long time things get gummed up, fuel lines crack and gaskets get dry and start to leak.

Denis