Reloading weed wacker string means replacing worn cutting line in the trimmer head so the tool can cut again. The method depends on head type: a rewindable spool you wind yourself, a pre-wound spool you swap in, or a fixed-line head that takes short pieces. Disconnect power first, match the line size the head is built for, load the line, and feed the ends out through the eyelets before you reassemble and test.

What reloading weed wacker string actually involves

A string trimmer, also called a weed wacker or weed eater, cuts grass and light weeds with polymer cutting line held in a spinning trimmer head. That line is a consumable. Sun, heat, rocks, fences, and ordinary wear snap it, fray it, or weld leftover wraps into a lump that will not feed. Reloading is the job of putting fresh trimmer line into the existing head so usable ends stick out through the eyelets again.

A successful reload looks simple from the outside: the cover is fully seated, any bump knob or spring is back in its place, and one or two equal lengths of line sit outside the head, short enough to clear the guard but long enough to cut. Inside, the line is seated the way that head was designed to hold it. On a rewindable spool, that means even wraps that can still unwind. On a cartridge-style head, it means a matching pre-wound spool with tails routed through the exits. On a fixed-line head, it means short pieces locked in holes, clamps, or channels.

This is not the same job as replacing the whole trimmer. You are not rebuilding the shaft, motor, or engine. You also are not automatically replacing the entire trimmer head. Many heads can be reloaded many times. You only need a new spool or a new head when the parts that retain or release line are cracked, rounded, missing, or melted.

The procedure changes by design because the line is stored differently. Some heads hide a rewindable inner spool. Some accept a drop-in factory-wound spool. Some have no spool at all. Brand-specific fastener styles, spring locations, and line capacity belong on the head markings or in the owner’s manual, not in a single universal winding ritual. Identify the head first, then follow the matching method.

Identify your trimmer head type first

Forcing a bump-feed rewind onto a fixed-line or cartridge head wastes time and can break clips that were never meant to come apart that way. Spend a minute looking at the head before you cut any line.

Bump-feed, auto-feed, and fixed-line heads

A bump-feed head is the most common consumer pattern. While the head is spinning, you tap the center knob on the ground and more line pays out through the eyelets. That knob, often called a bump knob, is a clue you are dealing with a spool inside a housing, not a ring of locked short pieces.

An auto-feed head also stores line on a spool, but it advances line without a deliberate bump. The outside may look similar to a bump-feed head, so the difference is how line is released in use, not only how the cap is shaped. Both types still need the inner line loaded correctly or they will not advance.

A fixed-line head uses discrete short pieces pushed through holes or locked in slots, clamps, or channels. There is no inner rewind spool to wind. You will usually see several insertion points around the rim instead of one or two eyelets feeding from a hidden reel. If leftover stubs sit in those holes and there is no removable disc of coiled line, treat it as fixed-line.

Rewindable spool versus pre-wound replacement spool

After you open a bump-feed or auto-feed head, look at the inner disc. A rewindable spool is meant to be reused. It typically has a slot, hole, or notch to catch the inner end of the line, molded arrows for winding direction, and often a divider wall if it is a dual-line design. You discard the old line and wind new line onto that same spool.

A pre-wound replacement spool is a cartridge or factory-wound disc you swap as a unit. It already has line on it and factory tails. Compare hub shape, divider, tail notches, and how the old disc sat in the housing. A similar-looking disc from a different head family may not seat, may not catch the drive dogs, or may send tails to the wrong exits.

Single-line and dual-line heads

A single-line head sends one cutting end out through one eyelet. A dual-line head sends two ends out opposite eyelets. Count the exits before you cut line. Dual-line rewindable spools often have a center divider and two winding channels so the wraps do not fight each other. Dual-line fixed heads usually take two or more separate pieces spaced around the rim.

Marks on the spool, cap, and housing

Do not guess the line path. Look for arrows, “this way” molding, line-size stamps, and simple diagrams on the spool face, the inside of the cap, or the housing. Those marks tell you winding direction, which notch holds a tail, and sometimes the diameter the eyelet can accept. Photograph the head before you take it apart so you can put springs, washers, and the bump knob back in the same order.

Safety steps before you open the head

Never open or load a head while the tool can still start. A spinning head can cut fingers, fling a loose cap, and throw cut line or grit toward your face. Work on a stable surface, keep bystanders and pets away, and treat the cutting path as live until power is isolated.

  • Battery models: remove the battery and keep it away from the tool until the head is closed and the guard is on.
  • Corded electric models: unplug the cord at the tool or the outlet so a bumped switch cannot start the motor.
  • Gas models: switch the tool off and disconnect the spark-plug lead so an accidental pull of the starter cannot fire the engine. That is a consumer precaution, not a full shop lockout procedure.

Let a recently used gas trimmer cool. The muffler, engine shroud, and even a head that has been rubbing the guard can be hot enough to burn skin. Wear eye protection. Cut line ends, spring-loaded caps, and packed debris can jump when the cover comes off. Gloves help with frayed polymer and sharp eyelet edges. Do not assume the debris guard makes eye protection unnecessary.

If the head is jammed with melted line, the housing is cracked, or you cannot tell how the cap retains the spool, stop and check the manual for that head. If fasteners are seized, plastic is crumbling, or the drive connection to the shaft looks damaged, a qualified small-engine or outdoor-power technician is the safer next step. Do not start, trigger, or bump-test the trimmer while the head is open or the guard is off.

Choose compatible line diameter, length, and shape

The correct line diameter is the one specified on the head, the spool, the packaging of the original line, or in the owner’s manual. There is no single size that fits every consumer string trimmer. Using a much thicker line than the head is built for can bind in the eyelets, refuse to feed, or load the motor and drive more heavily than the design expects. Line that is far too thin may whip, break at the eyelet, or slip through the feed mechanism.

Read the stamp before you buy or cut. If the head and the leftover packaging disagree, trust the head and the manual for that tool. Do not mix badly swollen, brittle, or heat-welded old line with new line on the same wind. Old fused wraps act like a brake inside the spool.

How much line to cut

A rewindable spool has a limited cavity. Overfilling is one of the most common causes of later jams. Without a model-specific chart, estimate conservatively: cut less than you think you need, wind it, and stop while the wraps still sit below the rim of the spool and can still move. Dual-line heads need two equal lengths or one long piece folded as that spool’s divider requires. Follow any fold-or-split diagram on the spool rather than inventing a third path.

Fixed-line piece length is also head-specific. The housing, a molded ruler on the guard, or the manual usually shows how long each short piece should be. Pieces that are much too long slap the guard. Pieces that are too short may not reach the lock or may disappear into the hole when the head spins.

Round line and shaped line

Round line is the common default and feeds through most eyelets without a special orientation. Some heads also accept shaped line, such as twisted, serrated, or multi-sided profiles. Shape can change how the line feels in the eyelet and how it wears, but compatibility is still a head-and-manual question. If the eyelet is a simple round hole sized for a listed diameter, stay with that diameter first. Do not assume a specialty profile is required, approved, or universally better.

Reload a rewindable spool head

This is the most common DIY reload on consumer bump-feed and many auto-feed heads. The exact clips and springs vary, so treat every fastener detail as head-specific and keep parts in order as they come off.

  1. With power disconnected and the tool cool, note how the cover sits on the housing. Some caps unscrew. Others unclip when you press tabs. Do not pry against thin plastic until you have found the intended release.
  2. Remove the bump knob or cover and lift out the spool. Watch for a spring, washer, or small clip under or over the spool. Set those parts aside in the order they came out.
  3. Pull off leftover line. If wraps are welded into a solid ring, cut them free rather than forcing the spool. Discard line that is brittle, flattened, or heat-glazed.
  4. Check the empty spool. Confirm winding arrows, the inner catch slot or hole, and, on a dual-line spool, the divider and opposite channels.
  5. Cut fresh line to a conservative length that will fill the cavity without stacking above the rim. For dual-line designs, prepare two equal pieces or one folded piece exactly as the spool diagram shows.
  6. Secure the inner end in the spool’s slot or hole if one exists so the first wrap cannot slip. On a divided dual-line spool, start each side in its own channel.
  7. Wind tightly and evenly in the marked direction. Keep wraps flat, side by side, not heaped in the middle. Crossed or loose wraps are a frequent cause of later feed failure. Do not bury the inner end under a messy pile.
  8. Stop winding while you still have tails long enough to reach through the eyelets with extra to hold. Many spools have temporary holding notches on the rim; park the tails there so the coil cannot spring loose while you handle the disc.
  9. Seat the spool back in the housing in the same orientation it came out. Route each tail through its eyelet before you close the cover, or immediately after, depending on whether the head wants tails pre-staged in the rim notches.
  10. Reinstall the spring, washer, and bump knob or cap in the original order. The cover should sit fully home. If it will not close, the spool is overfilled, a tail is trapped under the rim, or a spring is out of place. Open it and correct that instead of forcing the cap.

There is no universal wrap count, soak-in-water requirement, or single rule that every cap unscrews versus every cap unclips. If the spool has no arrows, wind so that line will pay out when the head rotates in its normal cutting direction, then confirm on a brief test after the head is fully closed.

Install a pre-wound replacement spool

Some heads are faster to service with a matching pre-wound spool than with a full rewind. The new spool must match the head family and the line-exit layout, not merely look like a round disc of similar size.

  1. Disconnect power and remove the cover as you would for a rewindable spool. Keep the spring and any drive dogs or washers.
  2. Compare the old spool with the new one: hub shape, center hole, divider, tail notches, and which face sat toward the bump knob. If those features do not match, do not force the part in.
  3. Drop the new spool into the housing in the same orientation. Align any slots with the housing lugs or drive features.
  4. Pull the factory tails out and seat them in the eyelets so they cannot slip back inside when the cap goes on. Opposite tails on a dual-line head should exit opposite eyelets.
  5. Close the cap fully. Tails should remain visible and movable. If a tail disappears as you snap the cover, reopen and recapture it.

A pre-wound spool does not remove the need to match diameter and exit layout. It only skips the winding step. If the replacement uses a different line size than the head stamp, treat that as a mismatch even if the plastic disc fits the cup.

Reload a fixed-line head

Fixed-line heads do not rewind. They hold short locked pieces. The locking feature may be a molded channel, a cam, a clamp, or a through-hole that grips the line when you pull it back. Insertion direction matters. Follow arrows or a diagram on the head when they are present.

  1. Disconnect power. Pull remaining short pieces out. If an end is fused or mushroomed, cut it flush and push or pull the stub out rather than hammering it through the hole.
  2. Cut replacement pieces to the length shown on the head, guard, or manual. Keep pieces equal if the head uses more than one at a time.
  3. Insert each piece in the marked direction until it is fully seated in the lock. You should feel or see the line catch. A piece that slides freely both ways is not locked and can fly out when the head spins.
  4. Tug each piece from the cutting side to confirm it is retained. Trim only if the manual or a molded mark on the guard shows a maximum exposed length.
  5. Confirm every station that should hold line actually holds a seated piece. Running a multi-piece head with empty locks can unbalance the head and wear the remaining line faster.

Do not assume any line shape will lock in every fixed head. A profile that is too slick, too thick, or too thin for that clamp may never catch. If the lock is cracked or the hole is egg-shaped from wear, new pieces will not stay put and the head itself needs attention.

Reassemble, feed the line out, and check the cut

Put the head back together before anyone restores power. Covers, springs, and bump knobs go on in the same order they came off. The debris guard must be in place. An open head or a missing guard is not a test setup.

Pull the tails so equal, usable ends sit outside the eyelets. On a dual-line head, even them up. Exposed ends should be long enough to cut vegetation and short enough that they do not constantly slap the guard. There is no single correct measurement for every trimmer; use the guard as the practical limit. If a blade or cutoff slot is built into the guard, that feature is there to trim overlong line after the head is spinning, not a reason to skip the guard.

Restore power only after the head is closed. On many bump-feed heads, line advances only while the head is spinning, so tapping a still head may not click more line out. For a brief test, stand in a clear area, keep the cutting path away from people, pets, and hard objects, and bring the head up to speed. Confirm the head is balanced enough not to shake violently, the ends cut, and nothing is grinding or smoking.

If you need another adjustment, return the tool to the same power-disconnect state before you open the head again. A successful feed check means the line is coming out and the head is closed. It does not prove the whole machine is in specification.

When the head or spool needs replacement instead of just line

New line cannot fix a head that no longer retains or releases line. Stop reloading and look at the parts if you see any of the following.

  • Cracked housing or cover, especially around the eyelets, tabs, or bump-knob well.
  • Rounded or stripped spool hub that no longer turns with the head or no longer indexes in the cup.
  • Enlarged, grooved, or razor-sharp eyelets that fray every new end at the same spot.
  • A missing or collapsed spring under a bump-feed knob, so the mechanism cannot release or cannot reset.
  • Line melted into a solid mass that has also deformed the spool walls or welded itself to the housing.
  • Fixed-line locks that no longer catch, or holes worn so oval that pieces walk out.

A matching replacement spool is enough when only the inner disc is chewed up and the housing is sound. Replacing the whole head is more practical when the eyelets, cover tabs, and bump well are worn together, or when you can no longer keep the assembly closed. There is no set number of reloads after which a head “must” be discarded. Judge the parts in front of you. Compatibility is not universal across brands, so match the replacement to that head family rather than to a generic shape.

Troubleshooting if the line will not feed, stay wound, or cut cleanly

Most post-reload failures come from tails that were never captured, wraps that cannot unwind, or damage at the eyelet. Work through the simple mechanical causes before you assume the motor or engine is at fault.

Line snaps back inside after you close the head

The tails were not seated in the eyelets, or they were not parked in the rim notches while the cap went on. Open the head, recapture each end, and close it again. On a dual-line head, confirm each tail has its own exit. A single long loop stuffed through one hole will retract as soon as the coil relaxes.

A bump-feed head will not release more line

Common causes are an overfilled spool, crossed wraps, line welded from heat, a missing spring, or a still head that cannot advance until it is spinning. Disconnect power, open the head, and look for a solid lump or a wrap that climbed over the divider. Clear fused line, rewind flatter and a little looser in bulk, and confirm the spring is present and seated. Do not bump-test an open head to “see if it clicks.”

Line keeps breaking at the eyelet

The eyelet may be grooved or sharp. The line may be much too thin for that exit, or you may be cutting against chain-link, concrete, or stone that batters the same spot. Inspect the metal or plastic eyelet with a fingertip (power still disconnected). A ruined eyelet needs a new insert or a new head. Fresh line of the stamped diameter is the right first correction if the eyelet is still smooth.

The head chatters, will not spin up, or smells like hot plastic

Stop. Disconnect power and reopen the head. An overfilled or welded spool can lock the head so the motor or clutch works against a brick. Continuing to run it can overheat plastic and the drive. The head should turn freely by hand with the tool isolated. If it does not, remove line until it does. Smell of overloaded plastic, smoke, or a head that will not come up to speed is a reason to inspect, not to keep squeezing the trigger.

Carburetor, clutch, and electrical diagnosis are outside a string reload. If the head turns freely with new line installed and the tool still will not run normally, have the machine checked by someone who services that class of trimmer. Homemade metal cutting substitutes, removed guards, and defeated interlocks are not a fix for feed problems.

Quick recap

Reloading weed wacker string is a head-level consumable job. Identify bump-feed, auto-feed, or fixed-line design, and whether you have a rewindable spool, a pre-wound spool, or short locked pieces. Isolate power, let hot parts cool, and wear eye protection. Use the line diameter stamped on the head or listed in the manual, avoid overfilling, and get the tails through the eyelets before you close the cover. Replace a cracked head, ruined eyelets, or a missing spring instead of winding another coil into a mechanism that can no longer hold or release line.