Direct Answer: How to Change String on a Weed Wacker
To change the string on a weed wacker (string trimmer), first disconnect the power source, then remove the trimmer head or spool, clear out any old line, and cut a fresh piece of replacement line to the length recommended for your model (typically 10 to 25 feet depending on line diameter). Anchor the line in the spool’s slot, wind it tightly in the direction shown by the arrows, thread the ends through the eyelets, and reassemble the head before testing the feed mechanism. Always use the line diameter and type specified in your trimmer’s manual, because the wrong line can cause jamming, poor cutting, or damage to the motor.
Understanding Your Trimmer Head Type
Before you buy replacement line or start taking things apart, you need to know which type of trimmer head your weed wacker uses. The restringing procedure differs significantly between designs, and using the wrong method can waste line or break the head.
Common Types of Trimmer Heads
| Head Type | How It Works | How to Restring |
|---|---|---|
| Bump-feed (tap-feed) | You tap the head on the ground while running to release more line. | Remove the spool, wind line onto it, and thread both ends through the eyelets. The spring and bump knob must be aligned correctly. |
| Fixed-line (manual-feed) | Line is set to a fixed length and must be replaced or adjusted by hand when worn. | Open the head, insert a precut piece of line, and secure it in the locking slots. No spool winding is usually needed. |
| Auto-feed (automatic) | The trimmer automatically feeds line when the engine speed changes. | Wind the spool carefully with even tension and follow the arrow direction. Improper winding is the most common cause of auto-feed failure. |
How to Identify Your Head Type
Look at the trimmer head while it is off. A bump-feed head has a large knob or button on the bottom that you can press. A fixed-line head has small slots or holes on the sides where precut pieces of line are inserted. An auto-feed head usually has a smooth, enclosed design with no obvious release button. If you are unsure, check the manufacturer’s label on the shaft or the owner’s manual, and search for your exact model number online.
Tools and Materials Needed
Most restringing jobs require only a few basic supplies, and you likely already own most of them. Having everything ready before you start makes the process faster and prevents frustration.
- Replacement trimmer line in the correct diameter (usually 0.065, 0.080, 0.095, or 0.105 inches).
- Scissors or a sharp utility knife for cutting the line.
- Work gloves to protect your hands from sharp edges and old line fragments.
- Safety glasses to shield your eyes from debris and snapping line.
- A clean, flat work surface so small parts like springs and washers do not roll away.
- Your owner’s manual for model-specific line length and winding direction.
- Optional: a spool winder tool if your trimmer brand offers one, which makes winding faster and more even.
Choosing the Correct Line Diameter
Line diameter is measured in inches, and it directly affects cutting performance and engine strain. Thicker line cuts heavier weeds but requires more power and can overload a small electric trimmer. Thinner line is easier on the motor but breaks faster in dense growth. Check the trimmer head or the manual for the maximum diameter allowed. If no number is printed, a 0.080-inch line is a safe general choice for most residential gas and electric trimmers, but always verify with the manufacturer before use.
Step-by-Step Guide to Restringing Your Weed Wacker
The exact steps vary slightly by brand, but the following universal procedure works for the vast majority of bump-feed and auto-feed trimmer heads. Always start with the trimmer turned off and completely disconnected from its power source.
Step 1: Disconnect Power and Prepare the Work Area
Unplug the trimmer if it is electric, or remove the spark plug wire if it is gas-powered. This prevents accidental starting while your hands are near the cutting head. Lay the trimmer on a flat surface with the head facing up so you can see the spool and any release tabs.
Step 2: Remove the Trimmer Head or Access the Spool
Most bump-feed heads have two small tabs on the sides. Press both tabs and pull the spool cap straight off. Some models require you to unscrew a knob on the bottom of the head, while others use a small screwdriver to release a locking clip. If the head will not come apart, look for arrows or a diagram molded into the plastic that shows the release method. Never force the pieces apart, because the internal spring can pop out and be lost.
Step 3: Remove Old Line and Inspect the Spool
Pull out any remaining old line, and remove the spool from the housing. Check the spool for cracks, and inspect the spring and the bump knob for wear or damage. Clean out grass, dirt, and debris with a dry cloth. If the spring is stretched or the plastic is broken, replace the entire spool assembly instead of just the line.
Step 4: Measure and Cut the New Line
Cut a single piece of new line to the length specified in your manual. As a general rule, a 0.065-inch line needs about 15 to 25 feet, a 0.080-inch line needs about 12 to 20 feet, and a 0.095-inch or thicker line needs about 10 to 15 feet. If you do not know the exact length, wind the spool until it is full but not bulging, then leave about 6 inches of slack on each end for threading through the eyelets. It is better to use slightly less line than too much, because overfilling causes jams.
Step 5: Anchor the Line in the Spool
Look for a small slot or notch on the spool. Insert one end of the line into this anchor point, and hold it in place with your thumb. The line must be seated in the slot before you begin winding, or the tension will pull it free and the whole spool will unwind.
Step 6: Wind the Line in the Direction of the Arrows
Wind the line onto the spool in the direction indicated by the arrows molded into the plastic. This is usually clockwise, but it can be counterclockwise on some models. Wind tightly and evenly, keeping the coils side by side without overlapping. Overlapping coils cause the line to tangle and jam inside the head. If your spool has two separate chambers, wind the line in each chamber according to the arrows, and leave the ends loose enough to thread through the corresponding eyelets.
Step 7: Thread the Line Through the Eyelets
After winding, pull the loose ends of the line out of the spool and insert each end through the eyelet or hole on the outside of the trimmer head. The eyelets may be located on opposite sides of the head, or on the same side depending on the model. Pull the line through until you feel resistance from the wound spool, leaving about 4 to 6 inches sticking out on each side. This exposed length is what actually cuts the weeds.
Step 8: Reassemble the Head
Align the spool with the housing, making sure the spring, washer, and bump knob are all in their correct positions. Press the pieces together until the tabs click into place, or tighten the bottom knob firmly by hand. Do not overtighten, because that can make the head difficult to turn or the bump-feed mechanism impossible to press.
Step 9: Test the Trimmer
Reconnect the power source, hold the trimmer away from your body, and start it. Run it at full speed for a few seconds, then stop and check that the line is still properly exposed. For bump-feed heads, tap the head gently on the ground while the trimmer is running to confirm that new line advances. If the line does not feed, or if it flies out entirely, you likely wound it in the wrong direction or failed to anchor it correctly.
Troubleshooting Common Issues
Even experienced users run into problems after restringing. Here are the most common issues and how to fix them.
Why Does My New Line Keep Jamming or Not Feeding?
Jamming usually means the line was wound in the wrong direction, the coils overlap, or the spool is overfilled. Remove the spool, unwind the line, and rewind it carefully in the arrow direction with even tension. Also check that the eyelets are not clogged with melted plastic or debris, and that the spring inside the head is seated properly.
What Should I Do If the Line Breaks Immediately After Installation?
If the line snaps right away, you are probably using line that is too thin for the job, or the line is catching on a sharp edge inside the eyelet. Use the largest diameter line your trimmer allows, and smooth any burrs on the eyelet with fine sandpaper. Also make sure you are not cutting against hard surfaces like concrete or stone, which shatter the line quickly.
How Can I Prevent the Line from Tangling Inside the Spool?
Tangling is almost always caused by loose or overlapping winding. Keep constant tension on the line as you wind, and guide each coil next to the previous one. Never let the line cross over itself. Using a spool winder tool also helps maintain even tension.
What Does It Mean If the Trimmer Head Is Difficult to Turn After Restringing?
A head that is hard to turn usually indicates the spool is overfilled, the line is too thick for the housing, or the head was reassembled incorrectly. Remove the spool, trim a few feet of line off, and check that all internal parts are aligned. If the problem persists, the head may have a damaged bearing or gear, and the assembly may need replacement.
Tips for Line Selection and Maintenance
Choosing the right line and taking care of it will save you time and money over the life of your trimmer.
Round, Square, or Twisted Line?
| Line Shape | Best For | Trade-Offs |
|---|---|---|
| Round | General-purpose trimming around lawns and gardens | Smooth and quiet, but less aggressive on thick weeds |
| Square or star | Heavy weeds and overgrown brush | Cuts faster but wears quicker and is noisier |
| Twisted | All-purpose use with better air flow | Good balance of durability and cutting power |
How Line Diameter Affects Performance
Thicker line cuts heavier vegetation and lasts longer, but it also increases the load on the motor, reduces runtime on battery trimmers, and can overheat small electric models. Thinner line is easier on the machine but breaks more often. Match the line to both the trimmer’s power rating and the typical vegetation in your yard. When in doubt, consult the trimmer’s manual or the chart printed on the original spool.
Storage and Care
Store replacement line in a cool, dry place away from direct sunlight, because UV rays and heat make nylon brittle. Keep extra line in its original packaging or a sealed bag so it does not absorb moisture. Before each use, inspect the exposed line for cracks or fraying, and replace it at the first sign of wear. Clean the trimmer head after every few uses to prevent grass buildup from blocking the feed mechanism.
Frequently Asked Questions
How often should I change the string on my weed wacker?
There is no fixed schedule. Replace the line when the exposed ends become shorter than about 3 to 4 inches, or when the line breaks repeatedly. Heavy-duty trimming against fences and curbs wears line much faster than light grass trimming, so check the line before every session.
Can I use any brand of trimmer line in my weed wacker?
Yes, trimmer line is largely universal as long as the diameter and shape fit your trimmer head. However, some brands offer spools designed only for their own heads, so if you buy a pre-wound spool, confirm that it is compatible with your model. For loose line, any reputable brand with the correct diameter will work.
Do I need to remove the entire trimmer head to change the string?
Usually not. On most bump-feed and auto-feed heads, you only remove the spool cap or the bottom knob to access the spool. You rarely need to unbolt the entire head from the shaft unless you are replacing the head assembly itself.
Why does my weed wacker only feed line when I stop and restart it?
This is normal for auto-feed heads, which are designed to advance line when the engine speed drops. If the line does not advance during normal operation, the spool may be wound too tightly or in the wrong direction. Rewind the spool with slightly less tension and verify the arrow direction.
