Roll the Poulan riding mower onto a flat surface. Set the parking brake to prevent the mower from rolling.
Lift the cover for the engine and remove the spark plug, using a socket wrench. This prevents the engine from starting while you are working on the unit.
Lower the mower deck.
Push in on the idler pulley underneath the engine. Pull the belt out from the pulley.
Remove the bolt from the housing on the deck. Remove the housing.
Push in on the pulley on the deck belt and pull out on the belt. Pay attention to the orientation of the belt so that you can place the new belt in the same position.
Wrap the new belt around the clutch pulley underneath the engine. Starting on the right side, feed the belt through the pulleys on the deck belt until tight.