Maintaining a gorgeous lawn begins with the maintenance of the equipment you use. Change or sharpen your mower blade yearly to offer the best cut possible. A dull blade tears at grass blades rather than cuts them. This damages the grass, leaving bare spots and an unhealthy looking lawn.
Disengage the engine by removing the spark plug wire from the plug. The mower will not accidentally start without a spark to the engine. Disengage the engine before beginning to safely change the mower blade.
Drain the oil and gas from the mower. Use a siphon to remove both the oil and gas. Use a separate siphon for each to prevent the two liquids from becoming combined. If the liquids become mixed and are re-entered in the engine, it will result in engine trouble. Remove gas without a siphon; simply mow the lawn until the tank is empty and the engine stops running. When you tilt the mower during the removal of the blade, these liquids will leak out if you don't remove them beforehand.
Place the mower onto its side on a workbench or the ground. Place a concrete block or garden paver behind the mower to prevent it from tipping over, and secure it in one location. Place a block of wood by the blade to prevent it from moving. Remove old grass and debris from under the mower using a gloved hand or a putty knife. Scrape the bottom of the mower with the putty knife to remove all the buildup from prior mowing sessions.
Turn the nut at the middle of the blade with a wrench until loose. Apply Liquid Wrench if the nut has become lodged and will not turn. Remove the block of wood, and hold the blade steady with a gloved hand. Continue to turn the nut while holding the blade steady until it is completely loose. Remove the nut and washers from the crank shaft holding the blade. Pull the blade off of the crankshaft. Make note of the placement of the blade, so you can install the new blade with the correct side up.
Position the new blade of the same size over the crank shaft, with the sharp edge turned in the same direction as the removed blade. Replace the nut and washers onto the crank shaft and tighten by hand, making sure the nut is snug. Turn the blade by hand several times to ensure it is securely attached. The blade should not waiver up and down.
Place the mower in an upright position on the ground. Clean any spillage from the painted surfaces of the mower. If any remaining gas or oil has leaked from the engine, it will peel the paint on the mower. Wipe with a degreasing cleanser. Fill the gas tank on the mower, and replace the removed engine oil. Attach the spark plug wire to the plug securely. Start the mower, and feel refreshed that the job is complete for another year.