When your MTD Yardmaster lawn mower continually dies while it is running even though the air filter is clean, the spark plug is good and there is plenty of gas in the gas tank, then the carburetor is usually gummed up with old gas and debris. All the gummed-up gas in the carburetor prevents any clean gas in your gas tank from being injected into the engine's piston. Cleaning the carburetor yourself will save you the mechanic fee.
Pinch the spring-loaded clamp holding the fuel line onto the carburetor with pliers and slide it down the hose 3 inches. The fuel line runs from the bottom of the gas tank to the carburetor.
Unscrew the gas cap on the MTD Yardmaster engine's gas tank. Pull the fuel hose off of the carburetor and direct it into the gas tank to prevent any gas from running out.
Point the carburetor cleaner spray can into the side of the carburetor on the engine and spray for 7 to 9 seconds.
Grab the bolt on the base of the carburetor with the pliers. Rotate it counterclockwise until it comes out. Pull the small can off the base of the carburetor. This can is the fuel bowl. Dump out any gummy gas in it and spray carburetor cleaner into the can and onto the flat above the can. Tighten the can back onto the base of the carburetor.
Push the fuel line back onto the carburetor. Pinch and slide the clamp back onto the end of the hose to secure it in place.