Things You'll Need
3/8-inch ratchet driver
The upper drive belt on the 42-inch Troy-Bilt lawn mower is the only serviceable drive belt on the mower deck. It drives the mower blades via a pulley system mounted on the deck and under the engine. The belt is a Kevlar V-groove belt that will eventually wear out. This is evident by the cracking on the V-groove side of the belt. Fortunately, Troy-Bilt made it easy to replace the drive belt without taking off the mower deck.
Locate the lift lever on the right rear fender. Lower the lever to the bottom notch on the fender. This maximizes space between the bottom of the lawn tractor and the top of the mower deck.
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Remove the screws that hold the belt guards onto the mower deck with a screwdriver and place the guards to the side.
Move the belt keeper rod from the PTO pulley mounted under the engine. Use a wrench to loosen one bolt, then use the wrench to remove the second bolt. Rotate the rod out of the way.
Draw a diagram of how the belt routes around the pulleys on the mower deck. This will help to ensure you reinstall the belt correctly.
Locate the idler pulley on the left side of the mower deck. The pulley secures to a mounting plate with a square hole cut into it and a spring mounted to it. Place a 3/8-inch ratchet driver into the square hole and rotate the pulley away from the belt.
Pull the belt off the pulley system and install the new belt onto the pulley system. Remove the ratchet driver from the pulley.
Place the belt keeper rod over the PTO pulley and secure it with the bolts. Place the pulley guards onto the mower deck and secure them with the screws.