How to Change the Line on a Troy-Bilt 4-Cycle Gas Trimmer

Turn off the Troy-Bilt trimmer and allow the engine to cool.

Disconnect the spark plug wire from the spark plug by pulling on the black rubber boot that covers the tip of the spark plug.

Turn the trimmer upside down, so that the cutting head is facing upward.

Rotate the inner spool counterclockwise until the arrow on the spool lines up with the arrow on the cutting head.

Grab onto one of the existing polypropylene lines where it is visible near the center of the spool with a pair of needle-nose pliers, and pull out the old line. Repeat with the other section of old line.

Insert one of the new pieces of polypropylene line into the hole in the side of the cutting head. Guide the line into the head until it appears in the opening near the center, and pull out a few inches with needle-nose pliers. Slip 1/2 inch of the end of the line into the line-locking hole located just slightly outward from the center of the spool from where the string is seated. Once the tip of the string is inserted into the line-locking hole, pull firmly on the length of line from outside the head to lock the line in place.

Repeat the previous step with the second section of new line on the other side of the trimmer head.

Hold the outer cutting head securely with one hand and rotate the inner spool counterclockwise to wind the exposed line onto the spool. Keep winding until only 6 inches of exposed lines remain outside the head. Pull tightly on the two lines to remove any slack around the spool, and rotate the spool again if more than 6 inches is exposed after pulling on the lines.

Turn the trimmer back over so that the cutting head is facing downward. Reconnect the spark plug wire to the spark plug. Start the engine and test the trimmer.