You can find pull rope starting mechanisms on dirt bikes, mini-bikes, pocket bikes, snowmobiles, go karts and quad-runners. The pull starter assembly consists of a rope spool, spring, rope and ratchet mechanism. Once pulled, the engine turns over and ignites from the spark and fuel mixture. Unfortunately, the rope gets pulled too hard sometimes and snaps at the handle or spool location. Sometimes the spring band become unhooked or breaks at its connection point. Any dirt bike owner can easily repair his pull start by using a few basic tools and following some repair steps.
Set the dirt bike upright and engage it in first gear to immobilise it. Locate the side cowl, also called the pull-rope case, on the side of the engine. It will be either plastic or metal and have a circular profile. Look for the three or four mounting bolts that hold the cowl to the engine. Loosen and remove the bolts with a socket and wrench. Pull the cowl away and set it on a work bench, inside facing up.
Locate the end of the rope. If the rope sits inside the cowl case in disarray, it means the rope has snapped from the handle end. Coil the rope back around the spool. Take the end of the rope and cut it cleanly with scissors. Melt some wax on the end of it to keep it from fraying, with a lighter and candle.
Turn the spring-loaded spool against the spring pressure and hold it when it won't wind anymore. If the rope has snapped at the spool end, run the prepared rope end through the spool hole, knot it and rewind it around the spool.
Lock a pair of locking vice grips onto the winding spool lip, while you hold the spring pressure with the other hand. Wedge the vice grips inside the casing so the spool will not turn. Place the waxed end of the rope through the casing hole. Thread the rope through the pull handle and knot the end twice. Place the cowl back onto the engine and insert the mounting bolts. Tighten the cowl bolts with a socket and wrench. Pull the rope to start the engine.
Remove the two screws on the screen with a screwdriver or small socket to access a defective ratchet spinner. Pull the spinner cap off. Use WD-40 lubricating spray and a rag to clean the ratchet assembly, the shaft and the ball bearings inside and out. Replace the ball bearings in the exact slot they came out of. Replace any mashed or deformed ball bearings.
Replace the spinner cap over the shaft and place the screen back into position. Insert the screen screws into their threads and tighten them with a screwdriver or small socket. Place the cowl back onto the engine and insert the mounting bolts. Tighten the mounting bolts with a socket and wrench. Pull the rope to start the engine.
If the band spring has broken inside the cowl, you will have to order one or pick one up at a dirt bike or lawnmower shop. Coil the spring back onto the spool and connect the spring end to the anchor notch in the case. Coil the rope around the spool and wind the mechanism.