Yardworks is a brand owned and operated by MTD Manufacturing, and is marketed primarily in Canada. Yardworks manufactures many of the same pieces of equipment manufactured in MTD plants, including push mowers. Yardworks mowers have a front driven self-propelled gear drive that works off a belt system. As the belt ages, the tensioner runs out of room to compensate. When this happens, you must replace the belt.
Run your Yardworks mower until it runs out of gas. With it out of gas, check the oil filler cap to ensure it is tight. Remove the spark plug wire so your mower cannot power on while you work on it.
Remove the screws that hold the front-drive cover onto your Yardworks mower deck and then pull the cover off the deck. Place it off to the side.
Turn the tension screw on the transmission counterclockwise to loosen tension on the drive belt. With tension loosened, remove the belt from the drive pulley on the transmission.
Place the mower on its side and then pull the belt though the housing on the deck. Remove the belt from the pulley mounted between the deck and the mower blade.
Place the new belt on the pulley, and then pull the belt through the housing and extend it to the drive gear. Place the belt around the drive gear.
Tighten the tensioning screw clockwise to tighten the belt in place.
Place the cover onto the mower deck and secure it with both screws.
These steps may vary slightly depending on the particular model of your Yardworks mower.