Unscrew the recoil starter cover from the trimmer. Turn the cover over to fix the starter. Press down on the pulley and cut the old rope off the pulley and starter handle.
Let your thumb off the pulley slowly to unwind the recoil starter spring. Unwind the old rope and discard. Unscrew the pulley mechanism and remove it from the cover.
Flip the pulley over and take the recoil spring out of the pulley. Inspect both pieces for any damage and replace if necessary. Coat the starter post with a small amount of engine grease.
Set the recoil spring into the pulley and put both back onto the starter post. Fit the new starter rope into the center of the pulley. Thread the rope through the starter cover and the starter handle.
Tie two knots, one at each end. Wind all but 10 inches of rope onto the pulley. Twist the unwound section into a loop and pinch it. Wiggle the loop back and forth to hook the recoil spring back onto the pulley.
Rotate the loop and pulley about five times or until the recoil spring feels tight. Unwind the starter rope while maintaining pressure on the pulley. Let go of the pulley to allow the rope to rewind onto the pulley. Reattach the starter cover to the trimmer.