If it sputters and hesitates when the throttle is advanced from idle, but runs smooth when full, the idle is rich.
Lean out the low needle in small increments until it idles for a long time without this 'loading-up'.
How do you know it's overly hot? Did you measure the temp some way?
Old fuel will cause a flame out as well as an old worn-out plug.
If the prop isn't balanced and the tank not cushioned, the fuel can foam from the vibs causing a leanout at full throttle.
Does the compression feel strong?

Kirk