The John Deere SB14 is a walk-behind push mower equipped with a self-propelled rear wheel drive transmission. The transmission works off a reduction pulley mounted between the mower blade and the bottom of the mower deck. A lever on the deck engages the clutch in the transmission and forces the mower to move forward. As the belt ages, the belt starts to slip, and the wheels do not move properly. When this happens, you can easily replace the belt with a new one.
Remove the black belt guard from the rear top of the mower deck by removing the two Phillips screws that hold it in place with a screwdriver. Place the cover off to the side.
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Loosen the tensioner bolt on the transmission with a screwdriver to increase the amount of slack in the drive belt.
Slip the drive belt off the pulley, and force it through the hole in the mower deck.
Place the John Deere mower on its side so that the air filter faces upward.
Pull the belt through the remainder of the deck, and pull the belt off the pulley mounted under the deck.
Place the new belt over the pulley. Place it as far as you can through the hole in the deck.
Place the mower on its wheels, and then pull the belt completely through the deck.
Place the belt over the pulley on the transmission. Tighten the tensioner screw with the screwdriver.
Place the cover onto the mower deck, and secure it with the screws and screwdriver.