Quick Answer: Disconnect the spark plug wire for safety, identify your trimmer type (bump feed, automatic, or fixed spool), remove the spool by twisting the center cap or pressing the release button, clear old line debris, wind new trimmer line tightly around the spool following the directional arrows, thread the ends through the eyelets, and reassemble. Test by gently tapping the spool on the ground to feed new line.
Safety First: Before You Start Restringing
Before touching your trimmer, always prioritize safety. Disconnect the spark plug wire from the spark plug—this prevents accidental engine start if the trigger is bumped. Work in a well-lit, clean area like a workbench or garage floor where you won’t lose small parts. Wear safety glasses to protect your eyes from old line debris and wear gloves to protect your hands from sharp line edges.
Never attempt to restring a trimmer while it’s running or still warm from recent use. Allow the engine to cool completely. If your trimmer uses a battery, remove it entirely during restringing. Keep your user manual nearby—manufacturer-specific guidance may differ from general procedures.
Identify Your Trimmer Type: Know What You’re Working With
Not all trimmers load line the same way. Identifying your trimmer type is the crucial first step.
Bump Feed Trimmers (Most Common)
Bump feed trimmers are the most widely used residential design. These have a spool that winds line manually, with a small bump button on the underside of the cutting head. When you tap the button against the ground during operation, the mechanism advances fresh line. The spool typically has two eyelets (line guides) on opposite sides. Look for a center cap with a release button or tab—pressing this releases the spool.
Automatic and Semi-Automatic Trimmers
Automatic trimmers advance new line without tapping. These use a spring-loaded spool or internal mechanism that extends line as it wears. Semi-automatic designs use a combination: you tap to feed, but the trimmer automatically maintains line tension. These are less common in residential models but popular in professional equipment. Check your manual to confirm which type you own.
Fixed Spool Trimmers
Fixed spool designs have a cutting head that doesn’t rotate—the line wraps around a stationary post. These are simpler to restring but less common in modern trimmers. Look for a fixed mounting post inside the cutting head with no removable spool.
Choosing the Right Trimmer Line: Size and Length Matter
Using the wrong line diameter or length causes performance problems and safety hazards.
Line Diameter
Trimmer line comes in standard diameters. The most common are:
- 0.065 inches: Lightweight trimmers and electric models. Good for light grass and weeds.
- 0.080 inches: Most common for residential gas trimmers. Handles typical lawn and light brush.
- 0.095 inches: Heavy-duty trimmers for thick weeds and brush. Professional-grade equipment.
Check your trimmer’s manual or the spool housing for the recommended diameter. Using line that’s too thick can strain the engine and cause binding. Line that’s too thin breaks frequently. When in doubt, 0.080 inches is the safe default for residential trimmers.
Line Material and Length
Standard nylon line works for most applications. Some specialty blends reduce noise or add durability, but standard nylon is cost-effective and widely available. For length, most residential spool capacities require 15–20 feet of line. Check your manual or the spool itself—it usually lists the recommended length. Buying pre-wound spools eliminates guesswork, but reloading your own spool saves money and is straightforward once you understand the process.
How to Remove the Spool: Accessing Your Trimmer Head
Accessing the spool is simple but varies slightly by design.
For Bump Feed and Automatic Trimmers
Look at the center of the cutting head. You’ll see a cap with either a release button (usually on the bottom or side) or a slot for a flathead screwdriver. If there’s a button, press it firmly while turning the cap counterclockwise. The cap should untwist or pop off. If the cap has a slot, insert a flathead screwdriver and turn counterclockwise. Some designs use a hex nut—use an appropriately sized wrench.
Once the cap is loose, unscrew it by hand and set it aside. The spool will either drop free or remain loosely attached by a center post. Gently pull the spool away from the head housing. You should now see the empty spool and the eyelet guides.
For Fixed Spool Designs
Fixed spools typically require no removal—the line wraps directly around the post. You may only need to unscrew a guard or cover plate to access the winding area. Check your manual for design-specific steps.
Clearing Old Line and Debris
Before loading new line, remove all old line scraps and debris. Use your fingers or needle-nose pliers to pull out tangled bits. Blow out dust with compressed air or a small brush. A clean spool winds new line evenly and prevents jams. Check the eyelets for damage or cracks—hairline cracks can snag new line during operation. If damage is visible, replace the spool.
How to Restring a Bump Feed Trimmer: Step-by-Step
Bump feed is the most common design and the best starting point for learning the process.
Step 1: Measure and Cut Your Line
Measure the recommended length (typically 15–20 feet) from your spool of trimmer line. Use scissors or a utility knife to cut cleanly. A clean cut prevents fraying and makes threading easier. Slightly melt the cut ends with a lighter or match—hold the end near (not in) the flame for a second. The melted nylon seals the fibers and prevents unraveling. Let it cool before handling.
Step 2: Find the Directional Arrows
Look at the spool’s surface. You’ll see arrows molded into the plastic showing the winding direction—always clockwise or counterclockwise depending on design. This matters: winding against the arrow causes the line to unwind during operation. The arrows are your guide; follow them exactly.
Step 3: Wind the Line Onto the Spool
Insert one end of the line into one of the two eyelets. Pull the line taut and begin winding around the spool, following the directional arrows. Keep tension as you wind—tight, even wraps prevent tangles and ensure smooth feeding. Don’t bunch the line in one spot; distribute it evenly across the spool width as you go. Wind until you’ve loaded most of the line, leaving about 6–12 inches of free line extending from the spool.
Step 4: Thread the Line Through the Eyelets
With the line wound, insert the free end into the opposite eyelet (the one you didn’t start with). Pull this end taut so both ends extend equally—typically 6–8 inches each. These extending ends are what does the actual cutting, so even length matters for balanced performance.
Step 5: Secure the Line and Reassemble
Most spools have small notches or slots near the eyelets. Fit each free line end into these notches to hold them in place during reassembly. This prevents the line from unwinding as you reattach the spool. Place the spool back into the cutting head, aligning any guide posts or tabs. Screw the center cap back on by turning clockwise until snug—don’t overtighten, as this can crack the cap.
How to Restring an Automatic or Semi-Automatic Trimmer
Automatic trimmers differ in that the line doesn’t wind onto the spool the same way.
Line Loading for Automatic Designs
Instead of hand-winding, automatic spools often have a straight spool chamber. Insert the line end into the chamber opening and feed it straight through until it exits the other side. Some designs have a guide post in the center—wrap the line once around this post, then feed the ends into the respective chambers. The internal spring mechanism handles tension and feeding.
Length and Testing
Load slightly less line than you would for a bump feed trimmer—typically 12–18 feet—since the automatic mechanism doesn’t require as much reserve. Once reassembled, start the engine (outdoors and with safety glasses on) and let it run for 10–15 seconds. The auto-feed should advance fresh line without tapping. If it doesn’t, check your manual for adjustment procedures—some automatic mechanisms have a tension screw that needs calibration.
How to Restring a Fixed Spool Trimmer
Fixed spool designs are the simplest but are uncommon in modern equipment.
The Winding Process
With the guard or cover removed, you’ll see a central post. Cut your line to the recommended length. Tie a knot around the post or use the design’s built-in anchor point. Wind the line tightly around the post, alternating passes to build layers evenly. Some designs use a figure-eight pattern to prevent line overlap. Continue until the spool is full, leaving 6–8 inches extending.
Threading and Securing
Thread one end through each eyelet guide. Secure the free ends in any provided slots or notches. The line on a fixed spool is less forgiving than on bump feed—uneven winding or loose knots cause poor cutting performance. Double-check all knots before reassembling.
Reassembling and Testing Your Trimmer
Proper reassembly ensures safe operation and prevents line jams.
Final Assembly Checklist
- Confirm the spool sits flush against the cutting head housing—no gaps or misalignment.
- Check that both line ends extend evenly and are seated in their eyelet slots.
- Screw the center cap firmly but not excessively tight—hand-tight plus a quarter turn is usually correct.
- Visually inspect the entire cutting head for cracks or damage before use.
Testing the Trimmer
Reconnect the spark plug wire. Take the trimmer outdoors to a clear area away from people and obstacles. Start the engine and let it idle for 10 seconds to warm up. Hold the trimmer at a slight angle and gently tap the spool bump button (if you have a bump feed) on the ground. You should see fresh line extend from the eyelets. If nothing happens, stop the engine, disconnect the spark plug, and check that the line is properly seated in the eyelets and notches. If you’ve loaded an automatic trimmer, the line should feed without tapping—start the engine and wait 5–10 seconds for auto-feed to activate.
Once line feeds successfully, test cutting on light grass. Listen for even cutting sound and watch for balanced line length. If one side cuts differently than the other, the lines are uneven—stop, disconnect the spark plug, and trim the longer side to match.
Troubleshooting Common Restringing Issues
Line Won’t Feed After Restringing
The most common cause is improper seating in the eyelet slots. Stop the engine, disconnect the spark plug, and check that each line end is fully inserted into its slot—they should be seated snugly, not just resting loosely. If the lines look seated correctly, the notches may be damaged or the line may be wound too tightly. Try unwinding slightly and rewinding with less tension.
Line Tangles or Jams During Use
Tangling usually means the line was wound unevenly or against the directional arrow. Stop immediately, disconnect the spark plug, and remove the spool. Unwind and inspect for bunching or backwards winding. Rewind carefully, following the arrows and maintaining even tension throughout.
Line Breaks Frequently
Frequent breakage suggests the wrong diameter line or lines of unequal length. Confirm your trimmer’s recommended diameter on the manual or spool. If you’re using the correct size, check for sharp edges or cracks inside the cutting head or eyelets—these cut line during operation. Smooth any rough spots with sandpaper. Also ensure both line ends are equal length—unequal lengths cause one side to fray first and break.
Uneven Line Length After Initial Use
One side wearing faster than the other usually means you’re cutting at an angle rather than horizontally. Hold the trimmer level and use smooth, even passes. If both lines fray equally but unevenly, one eyelet may be higher than the other—a sign of spool misalignment. Reinstall the spool, ensuring it seats flush against the head housing.
Maintenance Tips to Extend Trimmer Life
How Often to Restring
Restring when line becomes noticeably short (typically 2–3 inches on each side) or breaks frequently. Regular residential use (mowing 1–2 times weekly) usually requires restringing every 3–4 weeks during the growing season. Heavy use or thick brush increases frequency. Keep spare spools loaded and ready so you can swap them quickly instead of restringing mid-season.
Storage and Care
Store trimmer line indoors in a cool, dry place—exposure to sun and heat degrades nylon. Keep line away from moisture and extreme temperatures. Store your trimmer in a dry garage or shed, not outdoors where rain and humidity accelerate corrosion. Before long-term storage (fall/winter), run your trimmer for 30 seconds to clear fuel from the carburetor, which prevents gum buildup.
Other Maintenance
Clean the cutting head regularly—remove grass clippings and debris after each use with a brush or compressed air. Check the spark plug annually and replace if fouled or worn. Keep the air filter clean; a clogged filter reduces power and makes the engine work harder. Change the oil as recommended (for gas-powered trimmers). These simple steps keep your trimmer performing and extend the time between restringing.
Frequently Asked Questions
What diameter trimmer line should I use?
Check your trimmer’s manual or the spool housing—it specifies the correct diameter. The most common sizes are 0.065 inches (lightweight electric), 0.080 inches (standard residential), and 0.095 inches (heavy-duty). Using the wrong size causes poor performance or engine strain. When unsure, 0.080 inches is the safe default for residential gas trimmers.
Can I wind the line in either direction on the spool?
No—always follow the directional arrows molded into the spool. Winding backward causes the line to unwind during operation, creating a safety hazard and rendering the trimmer unusable. The arrows show the correct direction for your specific design. Take 10 seconds to identify them before winding.
How do I know if my trimmer is bump feed or automatic?
Check your manual first. If unavailable, look at the cutting head: bump feed designs have a small raised button on the underside of the head (you tap this on the ground to feed line). Automatic designs lack this button. Also, automatic feed advances line without tapping when the engine runs, while bump feed requires manual ground contact.
My trimmer line keeps breaking. What am I doing wrong?
Check three things: (1) confirm you’re using the correct diameter line—using oversized line strains the mechanism; (2) ensure both line ends are equal length and extend evenly from the eyelets; and (3) inspect the cutting head and eyelets for sharp edges or cracks that cut the line during use. If all three check out, the line may be old or damaged—buy fresh line and try again.
