MTD manufactures several different models of rotary mowers, often called push mowers. MTD push mowers use a recoil pulley and a rope to start the engine. When you pull the rope, centrifugal force engages the recoil pulley on the main-shaft of the engine. This centrifugal force in conjunction with the main-shaft forces the engine to start. If the pull cord breaks, you have no way to start the engine.
Remove the metal recoil pulley-cover plate from the top of the mower with a socket set. This exposes the recoil pulley. If the rope is frayed but still intact, cut the rope into two pieces before you remove the cover. Place the piece of rope with the handle attached to it off to the side.
Slide the pulley off the main-shaft. If you cannot pull the pulley off the main-shaft, look for a setscrew located on the pulley. If you locate a setscrew, use a screwdriver to remove it and then pull the pulley of the main-shaft.
Pull the remaining portion of the pull cord out of the pulley. The pulley has a hole on the bottom of it. To remove the rope, pull it out of that hole.
Tie a knot into one end of the replacement nylon rope and then thread the rope up through the hole in the pulley. Wrap the rope around the pulley until you have approximately six-inches left unwound.
Slide the pulley back onto the main-shaft and secure it with the setscrew if necessary.
Thread the rope through the eyelet hole on the metal cover and then bolt the metal cover back onto the engine.
Pull the old rope out of the handle and then slide the new rope up through the handle. Tie a knot on the end of the rope and then tug on the handle to seat the knot into the hole in the top of the handle.