A Weed Eater lawn trimmer burns fuel to create power, which also creates an enormous amount of heat. Through several engine processes during normal operation, this engine heats gets vented away from the block and into the outside air. If the Weed Eater can't vent gases, it will quickly overheat.
Clean Air Passages
The air passages on a Weed Eater lawn trimmer regulate the breathing function of the engine. The air filter helps bring clean, cool air into the engine, and the muffler helps push heated gases away from the engine. If either of these passages get blocked or dirty, the engine won't regulate the incoming and outgoing air and will overheat. Remove the pad part of the air filter, and wash it in soapy water. Rinse under cool water, and let it dry thoroughly. Clean out the muffler and spark arrester screen with a wire brush.
Clean Cooling System
The cooling system on a Weed Eater engine also helps heat escape. Heat radiates outward, and cool air gets pulled in through the flywheel. Most Weed Eater lawn trimmer cooling systems are accessed through drive shaft removal. The cylinder cover on top of the engine also acts as part of the air-cooling system. All of these areas, including the starter system and flywheel, need regular cleaning to prevent trapped particles from blocking the air supply.
A Weed Eater lawn trimmer operates on a two-cycle engine, which requires a pre-mixed fuel. This fuel combines the engine oil to keep the crankcase and piston adequately lubricated. If this mixture is off and there's too much gas in the mixture, the fuel will burn at a higher temperature, causing the engine to overheat. Mixed fuel can also separate and go bad after 30 days. As the oil separates from the gas, it will float to the bottom of the mix and the mixture will be too lean. Follow a strict 40-to-1 gas-to-oil ratio.
After cleaning the air and cooling systems and checking the fuel supply, it may be time to readjust the carburetor, especially if the engine is still overheating. The carburetor on a Weed Eater brand lawn trimmer uses three adjustable screws to regulate the amount of gas at a given engine speed. If too much gas is being used, the engine will speed up and run hot. Weed Eater requires that carburetor adjustments be performed by a service professional.