To restring a weed wacker, disconnect the power, open the head, wind new line of the size your manual specifies in the arrow direction, and reassemble.
What to do before you restring a weed wacker
Trimmer heads vary a lot, so the manual and the markings on your head outrank any general guide, this one included. That applies to line size, line length, the way your head opens and any safety limits. Take two minutes to set up first, because a spring-loaded spool can pop out when the head opens.
Disconnect the power source first:
- Gas: turn the engine off, let it cool, then pull the spark plug boot off the plug.
- Corded electric: unplug the cord from the outlet.
- Battery: remove the battery pack from the trimmer.
Gather these items:
- New trimmer line in the diameter your trimmer specifies
- Scissors or side cutters
- Work gloves and eye protection
- The manual, or the model number so you can look it up
Use only nylon trimmer line. Metal wire, rope and fishing line can break apart and throw fragments. Keep the cutting guard in place whenever you run the trimmer.
What size and how much line does your trimmer take?
Look for the maximum line diameter stamped on the head or printed in the manual. Common homeowner sizes are .080 in and .095 in, and heavy-duty heads take larger line. Line thicker than the head allows adds drag and strains the motor, so treat the stamped number as a ceiling. Thinner line fits, but it wears faster and cuts less, so match the stamped size when you can.
For length, use one rule: cut what your manual gives for your head. Spools differ in size and heads load differently, so no single number fits every trimmer. If you can’t find a length, wind until the line sits just below the rim of the spool flanges, leaving enough room for the head to close without pinching line.
| Head type | How you load it | What to check |
|---|---|---|
| Bump-feed (dual line) | Open the head and wind line onto the spool | Arrow direction, line length, and the notches that hold the ends |
| Fixed-line | Cut separate pieces and push each through a hole or slot | That both pieces are the same length |
| Quick-load (no disassembly) | Feed line through the eyelets and wind it by turning the knob or crank | Winding arrow on the head and how much line to leave outside |
Many dual-line bump heads take a single piece folded at its midpoint. If so, cut a piece twice the per-side length your manual gives, so each half matches the other.
Round, twisted or square line
Round line is the standard choice for light grass. Twisted line is a common pick when you want less noise. Square or shaped line has edges that cut tougher growth better. For dense weeds, a shaped line helps, but only within your head’s diameter limit.
How to restring a bump-feed head step by step
Most homeowner trimmers use a bump-feed head, where tapping the head on the ground releases more line. The release method differs by brand, but these nine steps cover the usual sequence.
- Disconnect power. Unplug, remove the battery, or pull the spark plug boot.
- Open the head. Squeeze the side tabs or unscrew the knob. Hold the housing while you lift the cap so the spring doesn’t launch.
- Remove the spool and old line. Note how the spring and any washer sit, and keep them inside the head so they don’t get lost. Brush out grass and debris.
- Cut the new line to the length in your manual, either as one piece to fold or as two equal pieces.
- Anchor the line. Hook the folded midpoint into the notch in the spool divider. With two pieces, push one end of each into its own anchor hole.
- Wind along the arrow. Turn the spool in the direction of the arrows printed on it or inside the head. Those arrows match the way the head spins, so the line pays out correctly. Keep the line tight, in neat side-by-side rows, with each half on its own side of the divider.
- Secure the ends. Push each end into a holding notch, leaving a few inches sticking out.
- Reassemble. Thread each end through its eyelet, set the spool and spring back in, and close the head until it clicks.
- Release and test. Gently pull the line out of the notches, reconnect power, and run the trimmer to confirm the line advances.
Rules for a clean wind
- Wind both lines in the same direction on a dual-line spool.
- Keep each line on its own side of the divider so they never cross.
- Pull the line snug as you wind, because loose coils trap the line later.
- Stop before the line passes the rim of the spool.
If the arrows are worn off, look in the manual or at the rotation arrow on the trimmer housing.
How to restring a fixed-line or quick-load head
Fixed-line heads
Fixed-line heads have no spool. Cut pieces of the length your manual gives, push each through its hole or slot, and pull so both ends stick out the same amount. Some heads hold the piece with a tab or a small knot, so follow the picture on the head. Uneven pieces make the head wobble, so compare the two lengths before closing it.
Quick-load heads
Quick-load heads let you skip disassembly. Feed one end of the line in one side eyelet and push it through until the same length comes out the other side. Then turn the knob or crank in the direction of the arrow to wind the line inside. Stop when a few inches remain outside on each side. The turning method is specific to each head, so check the markings on yours.
Check your work before you trim
Before you reconnect power, spin the head by hand to make sure it turns freely and nothing rubs. Compare the two line ends to confirm they stick out about the same amount. Make sure the cutting guard is attached and that neither end is trapped inside the head. A minute here saves reopening the head after a bad first pass.
Why trimmer line jams or won’t feed
Most feeding problems come from how the line was wound, not from a broken head. Match your symptom to the likely cause.
| Symptom | Likely cause | Fix |
|---|---|---|
| Line won’t come out when you bump | Line crossed or wound over itself, or too much line on the spool | Open the head, unwind, remove extra wraps so the line sits below the spool rim, and rewind neatly in the arrow direction |
| Line fused into a lump | Old or heat-softened line stuck together | Cut off the fused section or replace it with fresh line |
| Line is too short to reach | Ends pulled back inside the head | Open the head and pull the ends out through the eyelets |
| Line breaks constantly | Brittle old line, or worn eyelets with sharp edges | Install fresh line and inspect the eyelets for wear |
| Trimmer strains or bogs down | Line diameter above the head’s maximum | Switch to the diameter stamped on the head |
| Spool won’t spin or seat | Spring or washer out of place, or debris inside | Clean the head and reseat the spring and washer as they came out |
If the head is cracked, the eyelets are worn through, or the spool still won’t seat after cleaning, the head itself may be the problem. Our guide to weed trimmer replacement heads explains what to look for.
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Frequently Asked Questions
How often should I replace trimmer line?
Replace it when it turns brittle, frays, or gets too short to cut with, not on a set schedule. Rule: if it still bends without snapping and reaches past the guard, keep using it.
Can I use thicker line to cut tougher weeds?
Only up to the maximum diameter stamped on the head or listed in the manual. Thicker line adds drag and strains the motor. If you need more cutting power, switch to shaped line in the allowed size rather than a bigger diameter.
Why does my line keep breaking?
Hard surfaces such as concrete, fences and rocks wear line down quickly, so trim near them with a lighter touch. If it breaks even in open grass, check for brittle line or sharp, worn eyelets.
Can I use leftover line from a different brand?
Yes, if it is nylon trimmer line in the diameter your head allows. Brand matters less than diameter and condition. Use the same size for both lines on a dual-line head so the head stays balanced.
Do I restring a battery or electric trimmer the same way as a gas one?
Usually yes, because the head and spool work the same way. Only the power disconnect differs. Rule: if your head has a spool with arrows, follow the bump-feed steps.
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