The John Deere L120 features a powerful 22-horsepower, V-twin Briggs and Stratton engine, and a two-pedal hydrostatic transmission. The L120 is equipped with a three-blade, 48-inch cutting deck. The mower blades are attached to the three spindles that are mounted to the mower deck. The blades are made from aluminum, with an upper and lower bearing, and a steel shaft to which the mower blade bolts. If the spindle pulleys are bent or starting to pit from rust, it can cause the belt to break.
Remove all eight 10mm bolts from the two black plastic covers protecting the three spindles and pulleys found on top of the mower deck, using a 10mm wrench. This will expose the spindles and pulleys underneath.
Remove the large nut on top of one of the spindles. Turn on the air compressor and attach the air wrench to the compressor. Holding the spindle with one hand, place the air wrench on top of the nut, set the air wrench to the reverse setting and pull on the trigger. Once the nut is removed, slide the pulley off.
Inspect the pulley for pitting or wear. If damaged, slide a new pulley over top of the spindle, and reinstall the nut on top of the pulley with the air wrench. Repeat these steps for the other two identical spindles.
Reinstall the eight 10mm bolts to the two black protective covers, using the 10mm wrench.