Place the tiller on a hard, level surface. Pull the wire from the spark plug by grasping the boot of the wire with your fingers and pulling it away from the plug. Do not pull by the wire or you will damage it.
Push the drive lever on the pulley into the neutral position. Push on the belt pulley to create slack. Remove the belt from the drive pulley if it is still on the machine. Move the drive lever back into the forward drive position.
Squeeze the center of the new belt together to form a loop. Push the loop in between the pulleys and push forward on it. Push the loop over onto the bottom pulley of the Troy-Bilt tiller. Use a long screwdriver to assist in pushing the belt on the pulley.
Pull the top part of the belt up and loop it over the reversing disc. Put the drive lever into the neutral position on the tiller. Loop the top part of the belt onto the top engine pulley. Pull the belt over and loop it onto the lower engine pulley once you have it on the top pulley.