Can’t remive oringinal line head to put new one on my troybilt TB 525 EC trimmer. Can’t figure a way to lock it up so I can loosen head

SOURCE: line stuck inside head of troy-bilt trimmer

Take an awl or small diameter screw driver, same size or a bit smaller dia. than the line dia., and push it through the hole from the outside of the line head. This should push the piece of old line through the hole.
Recommendation: Leave at least one inch of line on the inside of the head, so you can grab it easily when you have to replace the line. I'll carry a pair of long nose pliers on me when I use my trimmer, so I can easily grab hold of the inside piece to pull it through.

SOURCE: Replacing the cutting head on Ryobi string trimmer.

There is a nut above the head, place a wrench on the nut then unscrew the head from the shaft, unless yours is different from mine this is how it works. I hope this helps.

SOURCE: I have a remington tap N go 12 weedeater. I

got to be a way to reload it

SOURCE: What is the fuel line size for Troy Bilt TB525CS Trimmer?

Yes, something special to know. If the new fuel line is going into the gas tank, be sure to cut a steep angle on the end of the line going into the gas tank. This will allow enough of the line to get into the tank where you will be able to grab it thru the gas fill opening with needle nose pliers and pull it thru.

Testimonial: "Thanks for the tip, I will try that when I find out the fuel line size."

SOURCE: Cannot disassemble Troy-bilt trimmer head

There is a round, rotary black part between the metal piece to which the cutting head attaches and the outer plastic seat of the cutting head. There are two square slots, each about a quarter inch wide, on opposites sides of the black piece. Slide an Allen wrench or something similar firmly into the slot. Holding the Allen wrench in a stable position, turn the outer plastic ring of the cutting head (it has scalloped edges that can be gripped firmly) counter clockwise to unscrew the cutting head from the bolt on which it is mounted. Be careful with the tool (e.g. Allen wrench) used to hold the black piece steady, as it is plastic and could be damaged by the edge of the tool.