Ryobi has made changing the line on its weed trimmers fairly easy. Whether the single-line or the dual-line trimmer, both models share the same design technology, which allows you to follow a few simple steps and change the trimming line in just a few minutes. No hand tools are required, and the process is quite easy to master.
Release the trigger to allow the trimmer head to stop rotating. Unplug or shut off the engine to the trimmer (depending on the model). Grasp the bump knob -- that's the line advance knob on the bottom of the cutting head -- in one hand and the trimmer head in the other, then twist the bump knob counterclockwise to remove it.
Remove the empty line spool located inside the trimmer head after the bump knob has been removed. Clean the trimmer head with a damp rag to remove any debris. Inspect the trimmer head and the line spool for any cracks or excessively worn parts. Replace if necessary.
Cut two pieces of replacement trimmer line approximately 2.4 m (8 feet) in length. Insert the end of the first piece of new line into the hole in the upper threaded part of the spool. Follow the small arrows on the spool to wind that line counterclockwise onto the spool, Secure the line temporarily by pushing it onto one of the slotted tabs on the upper spool.
Repeat the same process for the lower (empty) threaded area of the spool, but wind the line clockwise. Secure the line in the slotted tab directly opposite the first secured line.
Insert both lines into the small eyelets located in the trimmer head. Place the spool on the driveshaft. Release the two lines from their tabs by pulling each line out while pressing down on the spool.
Push down firmly on the spool to expose the threads located inside the driveshaft. Connect the bump knob to the threads located inside the driveshaft while still pushing down. Twist the bump knob clockwise to attach it securely. Test the trimmer to make sure it's operating properly.