To change a mower belt in a riding lawn mower, use a wrench and pliers. Move the lawn mower to a flat surface, and put the parking brake in place. Wear work gloves to keep your hands safe.
Allow the engine to cool, and unhook the spark plug. Place the mower deck in the lowest position, and turn the blade engagement lever off. Take the belt off of the engine pulley. With pliers, detach the bow-tie pins holding the right and left arms of the mower deck in place, and discard the other bow-tie pin attached to the front suspension arm.
To slide the mower deck out, turn the front wheels, and shift the mower deck lift lever to a higher position. Move the mower deck to the left, and after detaching the blade engagement cable, slide the mower deck to the right and pull out.
Unscrew the bolts from the pulley covers, and take the covers off. With a wrench, remove the nuts atop the pulleys, and pull the belt out of the mower deck. Slide a new belt through the belt guides, and re-screw the nuts to the pulleys. Reattach the pulley covers, and slip the mower deck back into the mower. Restore the blade engagement cable, and put the bow-tie pins back in place. Place the mower deck in the middle of the belt guide and the engine pulley. After testing the mower deck to make sure that it lifts properly, rewire the spark plug, and turn the mower on to check for proper installation.