Lawn Tractor: Blades Don't Spin When Engaged

The belt in your lawn tractor is driven by the drive shaft pulley, and is routed around all the spindle pulleys and the idler pulleys. A badly worn or stretched belt can slip, causing the blades to turn very slowly or not at all. This is relatively common, as belts tend to stretch over time and need to be replaced regularly. A seized shaft on a spindle can cause the pulley not to rotate, and this can cause the belt to snap. To replace the belt, lower the deck to its lowest setting and remove the belt guard by the drive pulley. Remove the belt from the pulley, and remove the pins that support the deck at the rear. Remove the front deck attachment point, and remove the pin that secures the PTO cable, then pull back on it to remove the spring. Now you should be able to slide the deck out from under the mower. At this point you can remove the covers from the blade spindles, and loosen the bolts on the idler pulleys so it is easier to slip the belt off between pulley and belt guard. If the belt has broken completely, make sure all the pulleys spin freely to avoid a second broken belt. To install a new belt, wrap it around the belt pulleys first, then back around the idler pulleys and tighten them down. Re-install the spindle pulley guards, and slide the mower deck underneath the mower itself. Re-install the PTO cable, re-attach the front deck, then the rear deck, and re-install the belt guard.

A seized pulley can cause the belt not to spin and therefore stop belt movement. This can also cause a belt to move, smoke and fail. To check for a seized pulley, first remove the drive belt from the engine pulley and lift the lever to engage the blades. When you engage the deck lever, it releases the brakes, allowing the spindles and pulleys to be spun by hand. At this point, check all pulleys for a growling sound, and determine if any of them feel tight. If so, you will likely need to replace the pulley. You can replace the bad pulley by simply removing the hold down nut on the top with a ratchet. If it is a mandrel, use a piece of wood on the blade to stop movement. If it is an idler, use an open-end box wrench to grip the nut underneath. Once the pulley has been removed and replaced, re-install each part in reverse order and re-attach the mower deck.

The spring’s job is to provide tension on one of the idler pulleys, and keep pressure on the belt to avoid slippage. Over time this spring can become weak, or break off from corrosion. To replace the spring, first remove the mower deck (follow instructions in the section regarding belt replacement if needed). With the deck off, locate the spring on the idler pulley assembly and pull off by looping a small rope around the end and pulling it off. Next, re-install the spring by using the rope to pull it back into position. Finally, re-attach the mower deck and your repair is complete.

To asses your lawn tractor’s cables, first put the mower deck in its lowest position and the clutch lever in the off position. You will need to access the clutch actuator assembly under the dashboard under the hood. There may be a fuel tank blocking access and, depending on your model, it may need to be removed and set aside. Once you have located the clutch actuator assembly, remove the hold down nuts and pull the handle off to remove the actuator from the steering housing. Remove the spring from the pin and detach the washer and cable. Using pliers, remove the tabs on the cable and detach it from the assembly. Remove the retaining pins that secure the support arms, and release the arms to detach the mower deck from the mower. Next, remove the belt from the drive pulley and belt guides, detach the clutch cable from the retainer, and pull the mower deck out. Use pliers to release the tabs on the clutch cable, and unhook the spring and remove the old cable. To install the new cable, hook the spring onto the idler arm and re-attach the cable onto the bracket. Slide the mower deck back under the tractor, re-attach the clutch cable and wrap the belt around the drive pulley and the belt guides. Re-attach all the support arms and re-connect the cable to the actuator using the spring and pin. Finally, re-attach the actuator to the dash and install the handle.

The mandrel is a unit with a shaft supported by bearings that transfers power from the pulley through the mower deck to the blades. If this shaft becomes seized it can cause the belt to break. To check for a seized mandrel, remove the drive belt from the engine pulley and lift the lever to engage the blades. When you engage the deck lever, it releases the brakes, allowing the spindles to be spun by hand. If any one of them is seized, it must be replaced. To replace the mandrels, start by removing the cover over the spindle. Using a piece of wood to hold the blade in place so it does not rotate, remove the spindle mounting nut, pull back the idler arm, and remove the pulley. Turn the deck over and remove the blade, before turning the deck back again, and removing the spindle mounting nuts. Remove the old spindle and install a new one with new mounting bolts. Turn over and re-install the blade, then turn the deck back and install the washer over the spindle shaft. Re-install the belt over the pulley. As you install the belt over the spindle shaft, tighten the spindle shaft bolt down, and secure the blade with wood to re-tighten, then re-install the spindle cover. Slide the mower deck back under the lawn mower and re-install PTO cable and spring. Finally, re-install all mounting pins and the drive belt.