How to String a Weed Eater Without Any Trouble
As an Amazon Associate we earn from qualifying purchases.
Stringing weed eater heads means replacing the used cutting line on the trimmer head with new line, wound on a spool and fed out through the eyelets so the head can cut again. The job takes a few minutes once you have the right line. Start by switching the tool off and confirming it is fully powered down, then check the line diameter and length your head requires, wind the new line in the direction the spool arrows show, and reinstall the spool and cover. The steps below follow the general sequence in manufacturer guidance, and the exact details vary by head type, so your model’s instruction card or manual should always be the final reference.
Quick answer
- Power the trimmer fully off and let it cool before you open the head, and keep it off the ground while you work.
- Use only the line diameter and length your head is designed for. The manufacturer instruction card or manual lists both.
- Wind the line in the direction the arrows on the spool show, keep it even and tight, and leave both ends the same length.
- Reinstall the spool and cover, pull the line through until it is taut, then run the trimmer briefly to confirm it feeds.
Before you start: safety and tools
The first step is always to make the trimmer safe to handle. Manufacturer guidance for STIHL trimmers says that before any maintenance the equipment should be completely powered off and cleaned of dirt and debris. On a cordless model, that also means removing the battery from the tool before you touch the head, because a switch can be bumped even when the trigger is not pressed. Work on a stable, flat surface, and wear gloves, since the cutting head and any loose line can have sharp edges.
You need very few tools. Most heads come apart by hand, though some use a small key or a cap that twists off. Keep the old spool or the empty spool handy so you can match its shape and the arrows on the rim. Have the new line or a replacement spool ready before you open the head, so the trimmer is not left apart for longer than necessary.
Choosing the right line for your trimmer
Line is not interchangeable across every head, and the wrong size is one of the most common reasons a head will not feed. Two numbers matter most. The first is the diameter, usually given in inches or millimeters, such as 0.065 inch or 0.080 inch. The second is the length of line the head holds. The STIHL product guidance tells owners to refer to the trimmer head instruction card to find the correct diameter and length, and it notes that not every line is compatible with every head.
Diameter affects both the cutting action and the strain on the motor. A thinner line cuts light grass and edges well, while a heavier line suits thicker weeds, but it also demands more from the motor and the feed mechanism. Do not go up in size unless your manual allows it. If the spool or the head shows a size, match that size first.
Some heads are sold as a complete replacement head with the line already wound and the spool included. These are useful when the old head is cracked or the eyelets are worn, because you swap the whole head rather than rewinding a damaged one. Other heads take bulk line that you cut to length and wind yourself.
Step by step: restringing a standard spool head
Use these steps for a common spool-style head with a removable cap. Your head may differ slightly, so check the arrows and labels on your model before you begin.
- Power down and remove the battery or spark plug wire. Confirm the trimmer cannot start while you work.
- Remove the cap. Turn the cap or press the tabs as your head is designed to open, and lift it away from the spool.
- Take out the old spool. Remove any remaining line and note which way the spool sits in the head, along with the arrows and the line size printed on the spool.
- Cut new line to length. Use the length your manual gives. For a dual-line head, cut two pieces to the same length so the cutting heads stay balanced.
- Find the center and the wind channel. Many spools have a center hole or a slot. Insert the line at the anchor point the spool shows, and leave a short tail sticking out.
- Wind in the arrow direction. Follow the arrows on the spool, winding tightly and evenly in the same direction every time. Winding against the arrows is a common mistake that can keep the line from feeding.
- Thread the line through the eyelets. Pass each end out through the eyelet on the head, keeping the two ends even if the head uses two lines.
- Reinstall the spool and the cap. Line up the tabs or arrows on the head and press or turn the cap back into place until it seats.
- Check the line length. Pull the line until it is taut and make sure it reaches the guard or the line limiter, without going past it.
- Run the trimmer briefly. Start the tool in an open area and let it spin for a few seconds. Line should release from the head. If it does not, stop the tool and check the winding and the eyelets.
Bump-feed and auto-feed heads
Many modern trimmers use a bump-feed or automatic feed system so you can release a short length of line by tapping the head on the ground while the motor is running. That is different from fixed-line heads, where you load pre-cut strips. The pack data for this post includes several cordless trimmers that describe these systems in their listing bullets. The listing for one 20V model describes a bump auto feed head that releases line with a tap, while a 21V model describes an auto line feed system that extends line when more is needed. These are feature descriptions from the listings, not guarantees of how a specific head will perform, so confirm the behavior in your own manual.
When you restring an auto-feed head, the spool still must be wound in the direction the arrows show, and the line still must match the size on the spool or in the instruction card. The feed system depends on the line moving freely, so a tangled or kinked wind will cause the feed to stick no matter how often you tap the head.
Common mistakes that stop the line from feeding
Most restringing problems come from a few avoidable errors. The first is winding in the wrong direction, which can leave the line jammed or prevent it from releasing. The second is using a line diameter the head was not built for, which can slip or break at the eyelet. The third is leaving the two ends uneven on a dual-line head, which causes the trimmer to vibrate and wear faster.
Another frequent error is overfilling the spool. If you wind too much line, the spool may not close, and the line will rub the cap and fail to release. Wind to the capacity shown on the spool, and stop before the spool is full. A fourth mistake is skipping the check at the end. Always run the trimmer briefly after reassembly, because a loose cap or a crossed line is much easier to fix on the bench than with the trimmer in the grass.
Watch the cutting head for damage as well. Cracks around the eyelets, worn holes, or a broken guard are reasons to replace the head instead of restringing it. A damaged head can throw line or fail under load, so inspect it each time you open it.
Safety while you cut
Once the trimmer is strung, wear safety glasses or goggles, long pants, closed-toe shoes, and gloves. Clear stones, sticks and debris from the area before you start, and keep bystanders and pets well back, because thrown debris can cause injury. Do not use the tool when you are tired or distracted. If you notice unusual vibration after restringing, stop the tool and recheck the head and the line before you continue.
Where to buy line and heads
When you buy replacement line, match the diameter and the spool type to your trimmer, and check the compatibility statement in each listing. The listings below are from our product data for this post. Each description reflects only what the listing states about the product, and you should confirm the diameter in your own manual before ordering.
-
An automatic feed trimmer in the pack describes “Auto Line Feed System” that senses line length and extends the line when more is needed, with two 2.5Ah lithium batteries and a 12-inch cutting path. The listing states a runtime of 40 minutes.
-
A 20V cordless trimmer in the pack lists a bump auto feed head that releases line with a tap, a 14-inch cutting width and a 4000mAh battery. The listing gives up to 60 minutes of runtime on low speed and 36 minutes on high speed.
-
A 24V cordless trimmer in the pack lists two 2000mAh lithium batteries, three replaceable blade types, and a telescopic shaft that adjusts from 33 to 47 inches according to its bullets.
Sources
STIHL: Wind and Replace String Trimmer Line
FAQ
Do I need to remove the battery before stringing a cordless weed eater?
Yes, on a cordless model you should remove the battery before you open the head or touch the cutting parts. The STIHL guidance in our source says the equipment should be completely powered off and cleaned before maintenance, and removing the battery is the simplest way to make sure the tool cannot start while your hands are near the head. Keep the battery and the charger away from the work area while you restring.
How do I know which line diameter to buy?
Check the instruction card that came with the trimmer head, the printed label on the spool, or the owner’s manual. The STIHL guidance points owners to the head instruction card for the correct diameter and length, and notes that not every line is compatible with every head. If you cannot find the information, look up your model number on the manufacturer’s support site before buying line.
Which direction should the line wind?
Wind the line in the direction the arrows on the spool show. Winding against the arrows is a common cause of line that will not feed. Keep the winding tight and even, and make sure both ends of a dual-line head are the same length before you reinstall the spool.
Can I use the same line in a gas and an electric trimmer?
Sometimes, but not always. Many heads accept a range of diameters, and the head and spool determine what fits. Check the instruction card or manual for your specific head rather than relying on a general statement that a line is universal. Our pack data includes listings that describe compatibility with several brands, and the listing wording is the only source we use for those claims.
Why does the line not come out after I restring the head?
The most common reasons are wrong winding direction, a line that is too thick for the eyelet, a spool that is overfilled, or a cap that is not seated. Open the head again, check each of these, and rewind the spool carefully. If the eyelets are cracked or worn, replace the head instead of continuing to restring it.
How often should I restring my weed eater?
Restring when the line is worn short, when the feed stops releasing line, or when the cutting becomes ragged. There is no fixed schedule because use, grass type, and line diameter all change how quickly line wears. Keep a spare spool of the correct size on hand so you can restring quickly when needed.
Bottom line
To string a weed eater reliably, power it off and remove the battery, match the line diameter and length to your head, wind the line in the direction the arrows show, and check the feed before you go back to work. If the head is damaged or the eyelets are worn, replace the head. For more background on choosing trimmers, you can read our guide to battery lawn mowers that are compared by features, and for setup help on matching gear to your yard, see how to match an electric mower to your lawn size.
