Troy-Bilt is a leading manufacturer of lawn equipment, and it offers a line of gas-powered string trimmers, including heavy-duty models with four-stroke engines and lightweight ones with two-stroke engines. As you do with any string trimmer, you periodically have to replace the line, and the method for doing this varies with the model. If you have a model with a fixed line head or a Click N Trim head, you can restring without disassembling the head to remove a spool, which is an convenience offered by few other trimmer manufacturers. If you have a standard bump-feed model, you do have to remove the spool to restring it.
When you go to the store to buy string, you'll find that it comes in various cross-sectional diameters, ranging from a dainty 0.080 inches, which is good for mowing short grass, all the way up to 0.155 inches, which you need for tough jobs, like brush clearing. It's important to check your user manual to make sure you get the right string for your model because if you overdo the diameter, you can damage the trimmer motor.
Replacing String on a Fixed-Line Head
The fixed head trimmer takes only a single short length of string, and unlike other heads that continuously feed string as you work, a fixed head has to be restrung each time the ends of the string wear short. The line is a beefy 0.105 inches in diameter, and it has a long reach, making it easier to trim in tight places.
String comes in precut short lengths rather than on a spool. To restring a fixed line head, you grasp the old string and pull it out. Then, you feed a new precut length through one of the holes on the side of the head, push until it comes out the other side and pull on the other end until both sides are even.
Restringing a Click N Trim Head
To restring a Click N Trim head, you'll need two equal lengths of string about 10 feet long. After disabling the trimmer by removing the spark plug wire, feed the end of one length through one of the holes on the side of the trimmer head and push until it comes out a hole on the opposite side of the head. Bend the end over and insert it into the hole next to the one from which the end just emerged to lock the string in place.
Install the other length of string in the same way and then hold the head cover with one hand while you crank the head counterclockwise to wind the string onto the head. Leave about 6 inches of string protruding from both sides. This is a bump-feed head, so the string will advance whenever you tap the head on the ground while the trimmer is running.
Restringing a Standard Bump-Feed Head
To restring a standard bump-feed model, you have to remove the spool, which you do by unscrewing and removing the bump knob and taking out the spool and spring. Feed a 10-foot length of string through each of the two holes in the top of the spool and pull them through until about 3 inches are left. Bend over the short end of each line and insert it into the adjacent anchor hole. Then, wind both strings around the spool in the direction of the arrow until about 6 inches remain.
When you replace the spool, feed the end of each string through the hole in the trimmer head and pull the string all the way through. Maintain tension as you set the spring and spool in place and screw the bump knob back on.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.