Introduction
If you have ever asked yourself Why Does Weed Eater String Keep Coming out? you are not alone. A bump‑feed trimmer head is designed to release line automatically when you tap the head on the ground, but several mechanical and user‑related factors can cause the line to feed continuously or jam. Understanding how the feed system works, recognizing the most common failure points, and learning how to adjust or maintain the head will save you time, money, and frustration. This guide walks you through the inner workings of a bump feed, the typical reasons line escapes uncontrollably, step‑by‑step diagnostics, proper adjustment procedures, line selection advice, maintenance best practices, common mistakes, and answers to frequently asked questions.
- How a Bump Feed Works
- Common Reasons String Keeps Coming Out
- Diagnosing the Problem
- Adjusting the Bump Feed
- Choosing the Right Trimmer Line
- Maintenance Tips to Prevent Future Issues
- Common Mistakes to Avoid
- When to Replace the Spool
- Professional vs. DIY Repair
- Frequently Asked Questions
- Conclusion
How a Bump Feed Works
A bump‑feed head contains a spool that holds the trimmer line, a spring‑loaded spindle, and a centrifugal clutch. When the head spins at operating speed, the clutch engages and the spool is locked in place. Tapping the head on the ground momentarily releases the clutch, allowing the spool to rotate freely. The spring then pushes a small amount of line out through the eyelets. Once you lift the head, the clutch re‑engages and the spool locks again. This mechanism relies on precise spring tension, correct line diameter, and a clean, undamaged feed path. Any deviation from the design specifications can cause the line to feed too much, too little, or not at all.
Common Reasons String Keeps Coming Out
Worn or Damaged Spool
Over time the spool’s internal ribs and the line‑guide channels wear down. A worn spool cannot grip the line securely, so the spring pushes line out continuously. Cracks or warping from heat also create gaps that let line slip past the retaining tabs.
Incorrect Line Diameter
Using a line that is thicker or thinner than the manufacturer’s specification changes the friction inside the feed channel. A thicker line jams the feed, causing the spring to over‑extend and release excess line. A thinner line offers too little resistance, so the spring ejects more line than needed.
Improper Winding Technique
Winding the line unevenly, crossing strands, or leaving slack creates loose loops that the spring can pull out in one motion. The line must be wound tightly, in the direction indicated on the spool, with each layer sitting flat against the previous one.
Damaged Feed Mechanism
The centrifugal clutch, spring, or retaining pawls can wear or break. A broken pawl cannot hold the spool, so every tap releases a large length of line. A weakened spring may not retract the line fully, leaving a permanent over‑feed condition.
Overheating During Extended Use
Continuous high‑speed operation generates heat that softens the plastic spool and the line itself. Softened components lose their grip, allowing the line to slide out more easily. Allowing the trimmer to cool periodically reduces this risk.
Debris and Grass Buildup
Grass clippings, dirt, and sap can accumulate in the feed eyelets and around the clutch. This debris acts as a lubricant, reducing friction and letting the line slip out. Regular cleaning keeps the feed path clear. (See Also:How To Start Weed Eater Stihl)
Diagnosing the Problem
Follow this ordered checklist to pinpoint why your trimmer line feeds excessively. Each step isolates a specific component.
- Inspect the spool visually. Remove the head and look for cracks, warping, or worn ribs. Replace if any damage is evident.
- Check line diameter. Measure the line with a caliper and compare to the spec printed on the head or in the manual. Swap to the correct size if needed.
- Examine the winding. Unwind a few feet and verify that the line lies flat, follows the arrow direction, and has no crossed loops. Re‑wind correctly if necessary.
- Test the clutch action. With the head off the shaft, spin the spool by hand. It should lock when spun quickly and release when you tap the head gently. If it stays locked or never locks, the clutch or spring may be faulty.
- Feel the spring tension. Press the spool inward; it should resist firmly and return smoothly. A weak or broken spring requires replacement.
- Clean the feed path. Use compressed air or a soft brush to remove grass, dirt, and sap from the eyelets and clutch area.
- Run a short test. Reassemble, start the trimmer, and tap the head on a hard surface. Observe whether a short, controlled length of line emerges. If line continues to feed, repeat the relevant step.
Adjusting the Bump Feed
Most bump‑feed heads allow a small adjustment of the spring preload or the clutch engagement point. Proper adjustment ensures the line feeds only the intended 1–2 inches per tap.
- Power off and disconnect the spark plug. Safety first.
- Remove the trimmer head. Usually a single bolt or a quick‑release collar.
- Locate the adjustment screw or nut. It is often on the side of the spool housing, marked with “+” and “–” or a small arrow.
- Turn the screw clockwise to increase tension (reduces feed length) or counter‑clockwise to decrease tension (increases feed length). Make quarter‑turn increments.
- Re‑install the head and test. Tap the head on concrete. If line still over‑feeds, increase tension another quarter turn. If line does not feed at all, back off a quarter turn.
- Lock the adjustment. Some models have a set screw to lock the position; tighten it once the desired feed is achieved.
- Reconnect the spark plug and resume work. Monitor the first few minutes to confirm consistent behavior.
Choosing the Right Trimmer Line
Line selection directly influences feed reliability. The table below compares the most common line profiles and their typical applications.
| Line Profile | Diameter Range | Best For | Feed Characteristics |
|---|---|---|---|
| Round | 0.065–0.095 in | General grass, light weeds | Smooth feed, low drag |
| Twisted | 0.080–0.105 in | Thicker weeds, moderate brush | Slightly higher drag, good cut quality |
| Serrated / Saw‑tooth | 0.080–0.115 in | Heavy brush, small saplings | Higher drag, may require stronger spring |
| Square / Star | 0.080–0.130 in | Commercial landscaping, dense vegetation | Aggressive cutting, higher feed resistance |
| Co‑polymer / Reinforced | 0.065–0.105 in | High‑heat environments, long runs | Retains stiffness, reduces melt‑back |
Match the line diameter to the head’s specification. Using a heavier profile than recommended often forces the spring to over‑extend, causing the exact symptom you are trying to solve.
Maintenance Tips to Prevent Future Issues
- Clean after each use. Blow out grass and debris from the head with compressed air.
- Lubricate the clutch sparingly. A drop of lightweight machine oil on the clutch pivot points reduces wear without attracting dirt.
- Inspect the spool monthly. Look for cracks, warping, or worn ribs; replace early.
- Store the trimmer upright. Prevents line from settling into a deformed shape on the spool.
- Rotate line stock. Use older line first; line that sits too long can become brittle.
- Check spring tension annually. Springs lose tension over time; a quick feel test can catch a weakening spring before it causes over‑feed.
- Follow the manufacturer’s winding direction. The arrow on the spool indicates the correct wind; reversing it creates immediate feed problems.
Common Mistakes to Avoid
- Over‑filling the spool. Packing too much line creates bulges that jam the feed eyelets.
- Using mismatched line diameter. Even a 0.005 in difference can change feed dynamics dramatically.
- Ignoring the winding arrow. Winding opposite to the arrow causes the line to unwind in the wrong direction, leading to snags.
- Tapping the head on soft soil. Soft ground does not provide the sharp impact needed to release the clutch cleanly; the head may bounce and release excess line.
- Running the trimmer at full throttle continuously. Sustained high RPM overheats the spool and softens the line.
- Neglecting to replace a worn clutch. A worn clutch slips unpredictably, causing both under‑feed and over‑feed.
When to Replace the Spool
Even with perfect maintenance, spools have a finite service life. Replace the spool when you observe any of the following: visible cracks or melting, ribs that no longer hold the line securely, a warped shape that prevents even winding, or a persistent over‑feed that cannot be corrected by spring adjustment. Most manufacturers sell replacement spools that are inexpensive and easy to install, often requiring only a single bolt.
Professional vs. DIY Repair
Many feed issues are resolved with the steps outlined above, which require only basic hand tools and a few minutes. However, if the centrifugal clutch assembly is damaged, the internal spring is broken, or the head housing is cracked, a professional repair shop can replace the entire head assembly quickly and guarantee proper torque specifications. Weigh the cost of a new head (typically $15–$30) against labor charges; for most homeowners, a DIY replacement is the most economical route.
Frequently Asked Questions
Why Does Weed Eater String Keep Coming out?
The most common cause is a worn spool or incorrect line diameter, which reduces friction and lets the spring push line out continuously. Cleaning the feed path and adjusting the spring tension usually resolves the issue. (See Also:How To Remove Weed Eater String)
How often should I replace trimmer line?
Replace the line whenever it becomes frayed, brittle, or when you notice a drop in cutting performance. For typical residential use, a fresh spool each season is sufficient.
Can I use any brand of line in my trimmer?
You can use any brand as long as the diameter and profile match the manufacturer’s specification. Using a different diameter will alter feed behavior and may damage the head.
What is the correct way to wind the line?
Follow the arrow on the spool, wind tightly in a single layer, avoid crossing strands, and leave a short tail (about 6 inches) for the initial feed.
Why does the line stop feeding after a few taps?
This usually indicates a weakened spring or a clutch that is not fully releasing. Inspect the spring tension and clean the clutch mechanism. (See Also:What Fuel Does Stihl Weed Eater Use)
Is it safe to adjust the spring tension myself?
Yes, provided the trimmer is powered off, the spark plug is disconnected, and you make small quarter‑turn adjustments. Over‑tightening can prevent any feed at all.
Conclusion
Understanding why your trimmer line feeds uncontrollably starts with knowing how the bump‑feed mechanism works and recognizing the most frequent culprits: worn spools, wrong line size, poor winding, damaged clutch parts, overheating, and debris. By systematically diagnosing each component, adjusting the spring preload, selecting the correct line profile, and following a regular maintenance routine, you can restore reliable, controlled line feed and extend the life of your equipment. Remember that the question Why Does Weed Eater String Keep Coming out? usually has a straightforward mechanical answer, and the steps outlined here will help you fix it quickly and keep your yard looking sharp.