Performing routine maintenance on your mower will ensure that it will last for many years. Most manufacturers recommend changing or sharpening the mower blade every two years. Mowing with a sharp blade will keep your lawn healthy and lush, especially if there are new seedlings planted. Dull blades will rip and tear the grass rather than provide a clear cut.
Siphon the gas from the tank using a siphon, or simply mow until the tank runs dry. The mower will tilt during the blade replacement, and the fluids will leak if they are not removed beforehand.
Detach the spark plug cord by firmly grasping the spark plug wire and twisting it while pulling it apart from the spark plug. This will ensure the mower cannot start while performing maintenance.
Turn the mower onto its side. Immobilize the blade with a block of wood by pressing the block of wood against the blade to ensure it cannot turn. Clean dead grass and debris from the bottom of the mower with a putty knife.
Disconnect the blade by removing the nut in the center of the blade. Turn with a wrench to loosen. Apply the wrench to the nut, and tap the end with a rubber mallet to loosen the nut if it is too difficult to turn. Remove the block of wood once the nut is loose. Holding the blade with your hand, continue to turn the nut to completely remove it. Slide the nut off the bolt. Remove the blade from the bolt. Make note of the blade direction in order to correctly replace it.
Change the blade with a new one of the same size. Position the blade onto the bolt, facing the same direction as the removed blade. Replace the nut on the bolt, and securely tighten it by hand.
Turn the mower upright. Place fresh gasoline in the tank. Reattach the spark plug cord to the spark plug by sliding the end of the wire over the plug. Press firmly to ensure a good connection. Your lawn mower is ready for a new cutting season with a fresh, sharp blade.