Turn off the mower. Locate the self-propelled drive cable support bracket. It is mounted on the mower handle near the deck.
Loosen the cable support nut, using an adjustable wrench. Turn the nut counter-clockwise until it is loose.
Pull down on the cable with your fingers, toward the mower deck. When the cable is tight, tighten the cable support nut, using an adjustable wrench. Turn the nut clockwise and tighten securely.
Start the mower to test the self-propel function. If the self-propel drive does not work as expected, repeat the adjustment procedure.