Easy, Illustrated Instructions on How to fix the pullcord on a Weed Eater
Attach and wind string
The string follows a path. You need to recreate this path with the new pink string. Start with a long piece of string, about four feet long. Loosen the black screw on the outside of the spool and remove the broken fragment of the white starter string.
You can use its stiffened form to remind you of what path the new string should take... or you can refer to the photo above. Wrap the new string along that same path and thread the string through the hole in the spool. Then wind the string around the spool until the string fills the spool. It doesn't have to be overflowing. Even with this thicker string, there is plenty of room on the spool for an appropriate amount of pulling string. Honestly, only about a foot (12 inches) of string is involved in the operation.
Looking at the spool from the black screw side, the string is wrapped clockwise.
Thread string through housing. Re-attach spool.
Replace the spool. The spool locks into the steel plate below it and onto a squared shaft for the motor. It isn't difficult to tell if it is seated properly. Push the end of the string through the starter cord hole, so that one end of the string will be hanging out when you re-assemble the green plastic housing.
My pink cord was frayed, which made threading difficult, so I used a piece of scotch tape to make the cut end a little sharper. Basically I made my own aglet.
Swivel the tiny black tabs back into place, holding the spool. Tighten those screws. I don't think it is possible for those screws to be so tight that they prevent the spool from turning, but check that it turns before you re-assemble the housing.
Push the green and black halves of this engine housing back together, taking care that the spool is still seated correctly. The torx screws go back in the black side, the hex screws go back into the green side.
These are the instructions for attaching the Weed Eater handle, the big one you use to hold the Weed Eater. The handle and trigger work together to yank on the steel throttle cable. It looks like a brake cable for a bicycle. Making sure that the trigger is arranged to pull the throttle cable, screw the halves of the handle back together.
Test string tension
You should now have a long string dangling out of the housing. Before you tie the little T-shaped pull handle on there, give the string a pull to see if it is turning the motor.
If it is, you can tie on the T handle and cut off the extra string. Ideally, your goal is to have the cord under a little tension at all times, so that the T handle is snug against the green housing before you pull it. The starting cord is most effective when it can be pulled about 16 inches, the difference between an outstreched arm and a bent one.
When you decide on a good place for the T handle, slip it onto the string and make a knot behind it. If it doesn't sit against the housing at rest, untie the knot and move the handle closer to the Weed Eater body. If you can't pull the cord out far enough to engage your whole arm in the pull, untie the knot and move the handle further from the Weed Eater body.
When you've got it set in a place you like, take it outside and start her up. The incredibly loud motor will signal your success to scores of your closest neighbors! Congratulations!