The Stihl FS 55 trimmer's starter rope is attached to a rotor inside the starter housing area. The rotor is also connected to the flywheel, which causes the engine to turn over. If the starter rope becomes "stiff," or doesn't rewind completely, you will need to replace it to get the flywheel turning again. You should also inspect the rotor, spring and other starter parts for signs of heavy wearing when you replace the starter rope.
Locate the starter rope at the rear of the engine, sitting directly under the starter housing cover. Loosen the cover's three retaining screws with the screwdriver. Pull off the cover and the starter rope will be connected to it on the reverse side. Clean the cover's vents and the rotor with the rag.
Pull about 6 inches of starter rope off the rotor. Push the starter rope into the notch on the side of the rotor. Hold the rotor with one hand and make a loop with the starter rope using your other hand. Twist the loop and the rotor clockwise until the recoil tension spring disengages from the rotor.
Unravel and snip off the starter rope with the scissors where it is knotted onto the rotor. Cut the rope just below the starter handle. Remove any remaining rope from the rotor and starter handle and throw it away. Inspect the rotor and recoil spring for any damage and replace them if necessary.
Push the new rope through the hole on the rotor, the starter housing cover and the starter handle. Tie the rope onto the rotor using an overhand knot tied just above the rotor hole. Tie another overhand knot above the starter handle.
Wrap the new starter rope around the rotor. Leave about 6 inches remaining. Push the starter rope up into the notch on the rotor. Make the end of the rope into a loop. Hold the cover while you wind the rotor counterclockwise seven times to engage the recoil spring.
Straighten out the starter rope while continuing to hold the rotor. Hold the starter handle. Release the rotor and slowly release the starter rope, which should retract automatically. If it doesn't retract, you will need to repeat the tensioning process.
Set the cover and starter rope in place over the starter housing area. Tighten the screws with the screwdriver to secure the cover and rope in place over the engine.
Always wear eye protection when installing or removing the recoil tension spring.