To troubleshoot common small engine problems, first ensure that the fuel tank is full of clean, fresh fuel and has an open shut-off valve. Next, remove dirt from the carburetor that can restrict the movement of air and fuel. Check for disconnected spark plugs; replace them if they are damaged, or after 25 hours of use. Also, check the valves and compression system to make sure that the valves have appropriate range of motion and there are no leaks present.
If an engine is stalling, check the freshness of the fuel, as stagnant gas begins to break down after a month. Replace the air filter if it is clogged or excessively dirty. Additionally, check the oil level and quality of the oil. Change the oil each season for best results.
If an engine begins to smoke, it can be caused by a dirty air filter in need of replacement. If the smoke is white or blue, the engine is burning oil. This can be caused by too much oil in the engine. Carefully remove some of the oil. If the engine is giving off black smoke, use a carburetor cleaner to remove debris from the carburetor and unclog any valves that may not be working properly.