There are three common belts on a mower deck. Because these belts are often exposed to the environment and then in storage for a couple of seasons out of use, these belts tend to dry and crack quickly. Unfortunately, we often take these belts for granted until one breaks and renders the riding lawn mower useless until we replace the belt. Checking the belts at the beginning of the mowing season is a better idea than at the end. Although these belts are pretty durable, they will start to show signs of wear after a couple seasons, depending on usage.
The top belt is the power clutch belt, also known as the PTO (power takeoff) belt. This is the easier one to replace because it's on top and has a spring-loaded hand lever to remove the belt from the lawn mower for deck removal.
The lower belt on the deck is called the arbor belt. This belt engages the pulleys on the deck and activates the blades. It is powered by the PTO belt and the upper pulley of the lawn mower.
The last belt and hardest one to replace the the tractor drive belt, located on the undercarriage of the lawn mower. Although there are too many models and makes to describe the removal process of every riding lawn mower, the principle of removing them would be similar. Removal of the deck would be extremely helpful when replacing any belt on the lawn mower. On some models you may not have to for the two lower belts, but it would still make the replacement procedure quicker and easier.
The Tractor Drive Belt
This belt is located on the undercarriage of the lawn mower and extends from the front motor pulley (which also powers the PTO belt) all the way back to the transaxle pulley at the rear of the lawn mower where the transmission is located. To replace this belt, the deck should be off the lawn mower. You'll crawl underneath and locate the idler pulley(s) and loosen the cap screw at the center of the pulley to allow a wiggling movement in the pulley. When loose enough, you'll be able to manipulate the belt off of the pulley and between the belt stop next to each idler pulley. Then, remove the belt from the transaxle pulley as well. To remove the front of the belt from the engine pulley, you may have to remove the cap screw from the center of the pulley and PTO to the engine crankshaft. (make sure the keys are not in the ignition, or unplug the PTO wire) and slide the belt up over the top of the engine pulley. Replacement would reverse the procedure.
The PTO Belt
The PTO belt is absolutely the easiest belt to change on your tractor. With the deck removed from the lawn mower (easier because the belt would already be removed from the PTO pulley) disassemble the idler pulley arm and remove the belt. Replacement of the belt would reverse the procedure.
The Arbor Belt
The arbor belt will require the removal of the upstop, the pulley shields or arbor covers and the tension spring from the idler pulley. Loosening the cap screw of the idler pulley to give it that same wiggling motion will allow you to slip the belt off of the pulley and remove it. Replacement of the belt is by reversing the procedure.