A self-propelled lawn mower moves forward on its own, providing a useful feature for people who have hilly yards, since the mower will do much of the work for them. A belt inside the engine spins around a series of pulleys that drive the cutting blades and forward motion. Check the condition of the belt every few months. If you notice your Sears self-propelled lawn mower belt looking frayed, it is time to replace it.
Disconnect the spark plug. Unscrew the screws holding the drive cover in place. Lift the cover off.
Pull the drive cable away from the anchor and unhook the return spring from the idler arm assembly.
Remove the hex bolt from the idler arm assembly. The idler arm should now be free to lift away. Remove the belt from around the drive pulley and idler arm assembly.
Lay the lawn mower on its side with the air filter and carburetor on the side facing up. Remove the screw securing the debris shield to the lawn mower.
Hold the cutting blade in place with a block of wood. Remove the bolt holding the cutting blade in place. Pull off the washers, cutting blade, adapter and debris shield. Remove the belt from around the engine pulley.
Wrap the new belt around the engine pulley and push the other end through the hole in the housing. Stand the mower back upright.
Wrap the belt around the idler arm assembly and the drive pulley, keeping the belt underneath the belt-keeper tabs.
Place the idler arm back on the assembly and secure it with the previously removed hex nuts. Lay the mower back on its side.
Put the debris shield tab back into its slot. Place the cutting blade onto the adapter, lining up the holes in each. Place the blade and adapter on the crankshaft. Put the washers on the bolt and secure the bolt tightly to the shaft. Stand the mower back up.
Attach the drive cable to the anchor. Hook the spring back up to the idler arm assembly. Place the cover back on and secure it with the previously removed screws.