Changing the blade on a Yard Man lawn mower is one way to help promote a healthy lawn. Dull and bent blades tear the grass blades, which invites disease and pests. Sharp blades cut the grass blades evenly, without undue stress to the grass. The Yard Man mower uses an adapter to help lock the blade into place upon installation. You can purchase new blades at home-improvement centers.
Place the Yard Man mower on a flat surface. Pull the boot off the spark plug. The boot is the portion that connects to the spark plug, and it will pull off with your fingers.
Tilt the mower on its side, with the carburetor, fuel-fill neck and air filter pointing to the sky. This will prevent fuel spillage.
Wedge the piece of board between the blade and the deck of the Mower. Put on a pair of leather work gloves, if you have not already done so.
Grab the mower blade between the cutting edge and the center bolt with one hand. Remove the center bolt, which secures the blade to the mower, with a socket wrench.
Pull the bolt and the blade bell support away from the mower blade. The bell support is the oblong, metal washer between the bolt head and the blade. Pull the blade off the engine shaft, and remove the blade adapter from the engine shaft.
Place some motor oil on a rag, and lightly lubricate the mower shaft with the oil on the rag. Lubricate the inner surface of the blade adapter with the oily rag.
Place the blade adapter over the mower shaft, with the star portion pointing away from the deck. Place the blade over the mower shaft, with the side marked "bottom" pointing away from the deck. Some blades will have the model numbers stamped on them rather than "bottom." The model number should point away from the deck.
Place the blade bell support over the shaft, flush against the mower blade. Thread the retaining bolt into the shaft until the bolt is hand-tight. Tighten the bolt securely with the socket wrench.
Place the mower back on all four wheels, and push the boot of the plug wire back over the spark plug.