Lawnmowers sputter and die out when they don't have the right mixture of air, fuel and spark to maintain optimal performance. Once this happens, restarting the lawnmower is often a difficult undertaking.
Moisture in any lawnmower tank or fuel line can cause sputtering. Once water has entered into the cylinder of a lawnmower, it keeps the gasoline from igniting properly. There are many things that can cause water to get into the tank or fuel line of a lawnmower, but the two most common causes are a loose gas cap or condensation forming inside the lawnmower. The best way to fix this problem is to completely drain the fuel tank and put in fresh gasoline. The gasoline removed from the lawnmower has to be disposed of properly.
A bad spark plug is another issue that causes lawnmowers to sputter. A lawnmower that has a bad spark plug is usually difficult to start, and once it is started, it runs poorly. Sometimes spark plugs can be cleaned with a wire brush instead of being replaced. If the owner chooses to clean the spark plug, the gap in the spark plug needs to be reset to manufacturer’s specifications to ensure proper functionality.