A McCulloch chain saw that won't keep running may have a major problem. Or it may be something fairly simple that a user can diagnose and correct on his own. Troubleshooting starts with checking fundamentals -- such as switches, fuel and spark plug -- and then perhaps making some corrections or adjustments. Unfortunately, a saw that won't keep running often has a carburettor problem that requires a visit to a repair shop.
Check basic components. Check the ignition switch to ensure it is in the "on" position and stays in that position. Ensure the gas tank is at least half full and that the fuel is properly mixed and not old. Fuel disintegrates when the saw sits for a prolonged period. If you are uncertain about the age or mixture of the fuel, empty the tank and refill it with a proper mixture.
Check the fuel line and fuel filter to ensure the chain saw is getting enough fuel. If the fuel line from the tank to the carburettor is kinked or split, replace it. Locate the fuel filter inside the tank and replace it.
Check the air filter inside the saw cover. If it is dirty, clean or replace it. Remove the muffler cover to check the spark screen arrester. Clean it gently with a wire brush and replace it if damaged.
Check your spark plug. If the spark plug is fouled or the plug wire is not properly connected, the engine will not fire. Remove the plug wire by pulling it straight off. Unscrew the plug with your scrench. If it is fouled with gasoline or carbon, either clean or replace it. If it is wet, it may indicate a serious carburettor problem that requires a professional.
Check the idle speed to ensure it is not too low. The idle adjustment screw is near the pull chain, marked "T." Turn it clockwise to increase idle speed. A properly idling saw will run smoothly but without causing the chain to move.