Weed eaters do overheat in some cases, especially if the airflow to the weed heater is restricted.
Even excessive strain on the weed eater engine and improper fuel mixtures can also result in a weed eater overheating.
Common causes of weed eaters overheating are debris, grass and other materials that clog the air intakes and cooling fins of the weed eater engine.
And having an incorrect fuel to oil mixture for the 2 stroke weed eater engine can result in the weed eater overheating and also using fuel that has too much ethanol can also result in the weed eater overheating
If there's not enough oil mixed with the gasoline then the weed eater motors internal parts won't get the proper lubrication and cause it to overheat.
And using the wrong size of weed eater string or running the weed eater engine at too high of speeds or trying to trim down dense vegetation can also result in undue stress on the engine and cause it to overheat.
Even a clogged spark arrestor on a weed eater can restrict the exhaust flow and result in overheating of the weed eater.