All pull start cords on lawn mowers, or any engine, will eventually break. It does seem to occur at the most inopportune time and can be very frustrating. Repairing the pull start cord will only take a few deep breaths and approximately 15 minutes to repair. Just a few hand tools are needed to rewind the cord back onto the spring mechanism. Of course, this repair maybe part of an annual ritual if you use the lawn mower quite often.
Use the 7/16" end wrench to remove the top, or side, pull cord starter housing. Typically the metal housing is held in place by three bolts. Two of those bolts are located on each side of the round portion of the housing. The third bolt is generally placed on the flat side, near the push handles of the lawn mower.
Lift the metal housing from the lawn mower engine. Turn it over so the spring loaded recoil pulley mechanism is facing upwards, towards you.
Wind the recoil mechanism, in a clockwise direction, to place tension on the spring as tight as you can.
Align the rope hole in the recoil pulley with the hole in the metal housing.
Place one of the hand spring clamps at the three o'clock position where the clamp will hold the pulley in place against the metal housing. Secure the second hand clamp in the nine o'clock position.
Cut the frayed end of the pull cord with the pocketknife. You will want a straight, clean edge to the rope.
Feed the newly cut end of the pull rope through the metal housing rope hole, and the hole in the recoil pulley.
Use the needle nose pliers to grab the end of the rope as you feed it through the pulley hole.
Pull enough of the rope through the pulley to tie a single knot in the end of the cord.
Pull the cord taunt, so the knot rests against the inside of the recoil pulley.
Hold onto the recoil pulley with your thumb, while removing the hand clamps. Allow the pulley to slowly recoil the rope. Reassemble the metal housing back onto the lawn mower in the reverse order from step 1.