Direct Answer: How to Replace Bump Feed Trimmer Line
To replace trimmer line in a bump feed head, first disconnect power (unplug electric trimmers or remove the spark plug wire from gas models). Remove the bump feed head by unthreading it from the shaft or unscrewing fasteners, depending on your trimmer model. Clean out old line debris from the spool, then wind new line onto the spool in the direction indicated by arrows on the spool (typically counterclockwise). Thread the line ends through the eyelets on the head, secure them in the notches, and reassemble the head back onto the shaft. The entire process takes 10–20 minutes for most trimmers.
Understanding Bump Feed Mechanisms
A bump feed trimmer head automatically advances line as it wears or breaks. When you tap (bump) the head on the ground during operation, a spring-loaded spool mechanism releases a small amount of new line. This design eliminates manual line adjustment and keeps the trimmer running longer between full line replacements.
The core components include:
- Spool: A cylindrical chamber that holds wound trimmer line
- Spring mechanism: Pushes the spool upward to advance line when bumped
- Eyelets: Small holes on the head guard where line exits and cuts grass
- Centrifugal clutch: In gas trimmers, this prevents the head from spinning when the engine is off
- Head assembly: The plastic or metal housing that holds all components together
Over time, the spool spring weakens, the plastic housing cracks, or the line wears down completely. Knowing which component is failing helps you decide whether to replace just the line or the entire head.
Safety Considerations Before You Start
Always disconnect power before servicing any trimmer. For electric models, unplug the trimmer from the outlet. For cordless electric trimmers, remove the battery. For gas trimmers, remove the spark plug wire by twisting and pulling the wire cap off the spark plug—this prevents accidental engine start.
Bump feed heads contain a centrifugal clutch mechanism (on gas models) or a spring-loaded spool (all models) under tension. If you reassemble incorrectly or fail to secure fasteners, the head can suddenly spin or release line unexpectedly. Always wear eye protection when testing the trimmer after reassembly.
If your trimmer is still under warranty, check the manual or manufacturer website before servicing. Some manufacturers void warranties for independent repairs. Professional service may be covered if the head is defective.
Tools and Materials You’ll Need
Gather these items before you begin:
- Replacement trimmer line: Match the gauge (diameter) and material type to your trimmer’s specifications. Common gauges are 0.065″, 0.080″, and 0.095″. Check your manual or the head housing for the correct size.
- Screwdrivers: Phillips and flathead, depending on your trimmer model
- Adjustable wrench or socket set: For removing the head from the shaft
- Needle-nose pliers: For manipulating small springs or clips
- Wire cutters or scissors: For cutting new line to length
- Clean cloth or brush: For removing debris from the spool and head
- Owner’s manual: Most critical—it specifies line type, gauge, winding direction, and line length for your model
If you don’t have your manual, search online for the trimmer brand and model number (usually printed on the motor housing or near the handle).
Removing the Bump Feed Head
The method for removing the head depends on your trimmer design:
Threaded Head (Most Common)
Many trimmers have heads that screw onto the shaft. To remove:
- Place the trimmer on a flat surface with the head facing up
- Hold the shaft steady with one hand (or use a wrench on the shaft collar if available)
- Rotate the head counterclockwise with your other hand until it loosens
- Continue unscrewing by hand until the head separates from the shaft
Bolted Head
Some models secure the head with bolts or set screws:
- Locate the fasteners on the underside or sides of the head
- Use the appropriate screwdriver or wrench to remove all fasteners
- Gently pull the head straight up to separate it from the shaft
Tip: If the head is stuck, spray penetrating oil (like WD-40) around the connection point and wait 15 minutes before attempting removal again.
Clearing Old Line and Preparing the Spool
Once the head is off:
- Remove old line: Use needle-nose pliers to pull out any remaining line wrapped around the spool. If line is tightly wound, carefully cut it with scissors and unwrap it.
- Clean the spool: Use a dry cloth or soft brush to wipe away dirt, grass clippings, and old line debris. If buildup is heavy, rinse the spool under running water and allow it to dry completely.
- Inspect the spring: Look at the spring mechanism beneath or around the spool. It should be intact, not bent or broken. If the spring is damaged, the bump feed won’t work properly even with new line, and you should replace the entire head.
- Check the spool housing: Look for cracks in the plastic spool or housing. Minor hairline cracks may not require replacement, but large cracks or missing pieces mean the head should be replaced rather than reused.
Winding New Line on the Spool
This is the critical step where mistakes cause the bump feed to fail. Follow these guidelines:
Determine Winding Direction
Most spools have arrows molded into the plastic showing the correct winding direction. Look carefully—the arrow indicates which way line should wrap around the spool. If no arrow is visible, consult your manual. If the manual isn’t available, the most common direction is counterclockwise, but this varies by brand.
Calculate Line Length
Your manual specifies the total line length needed (typically 15–25 feet depending on spool size). If you don’t have the manual, measure your spool diameter and consult online specifications for your trimmer model. It’s better to use slightly less line than too much—excess line won’t fit and won’t wind evenly.
Wind the Line
- Find the line anchor notch or slot on the spool (usually a small groove or hole on the edge)
- Insert one end of the line into the notch and hold it in place with your thumb
- Begin winding the line around the spool in the correct direction, keeping tension moderate—tight enough to prevent loose coils, but not so tight that you strain the line or spool
- Wind in neat, overlapping rows, working from one end of the spool to the other
- When you reach the end of your measured length, cut the line and secure the end in another notch or under the final coil
Common error: Winding line in the wrong direction causes the bump feed to advance line continuously (not just when bumped) or not advance at all. If this happens after reassembly, unwind and rewind in the opposite direction.
Threading Line Through Eyelets and Reassembling
Once the spool is wound:
- Identify the eyelets: Look for small holes or slots on the outer edge of the head housing where line exits. Most heads have two eyelets positioned opposite each other.
- Thread the line: Pull one end of line from the spool and thread it through one eyelet. Pull the other end through the second eyelet. Ensure line sits flat and isn’t twisted.
- Secure line ends: Most heads have small notches or clips that hold the line ends in place. Insert each line end into its corresponding notch. The line should be taut but not over-stretched.
- Check for interference: Rotate the spool by hand and verify that the line doesn’t rub against the housing or spring mechanism.
- Reassemble the head: If your head has a cover or cap, snap or screw it back into place.
- Reattach to the trimmer shaft: Align the head with the shaft and screw it on (clockwise for threaded models) or insert and secure bolts. Tighten firmly but don’t over-torque, which can crack the plastic.
Model-Specific Variations
While bump feed principles are universal, details vary across brands:
Ryobi Trimmers
Most Ryobi bump feed heads unscrew counterclockwise and wind line counterclockwise onto the spool. Ryobi typically uses 0.080″ or 0.095″ line. The spool has two eyelet slots and two line anchor notches. Consult your specific model manual, as some newer Ryobi models use semi-automatic heads that differ slightly.
DeWalt Trimmers
DeWalt heads often feature a snap-on design rather than threading. The spool typically winds clockwise. DeWalt recommends 0.080″ line for most models. The manual usually provides a winding diagram showing the exact path for line placement.
Echo and Stihl (Gas Trimmers)
Professional-grade gas trimmers from Echo and Stihl use robust bump feed heads designed for extended use. Line direction and spool capacity vary by model. Echo and Stihl provide detailed winding diagrams with each trimmer. These heads are more durable and often use reinforced spools, but the basic replacement process is the same.
Generic Electric Trimmers
Budget electric trimmers sold under various brands often use simpler spool designs. Check whether your model uses automatic bump feed or manual advance—the replacement process differs slightly.
Always consult your specific manual or search “[Brand] [Model] bump feed replacement” online for winding diagrams and line specifications.
Troubleshooting: When Replacement Isn’t the Answer
Before assuming the head needs replacement, diagnose the actual problem:
Bump Feed Stops Advancing Line
Possible causes and fixes:
- Spring weakened or broken: If the spring feels loose or doesn’t push the spool upward, replace the entire head. Springs cannot be replaced separately in most designs.
- Spool clogged with debris: Clean the spool and housing thoroughly. Dried grass or dirt can prevent the spring from moving freely.
- Line wound too tightly: Remove and rewind the line with less tension.
- Wrong line type or gauge: Using line that’s too thick or too thin for your spool can jam the mechanism. Replace with the exact gauge specified in your manual.
Line Tangles or Bunches
Possible causes and fixes:
- Line wound in wrong direction: Unwind and rewind counterclockwise (or according to your manual).
- Line not secured in eyelets: Ensure both line ends are fully threaded through eyelets and seated in the anchor notches.
- Spool deformed: If the spool is warped or cracked, replace the head.
Head Leaks or Loses Line During Operation
Possible causes and fixes:
- Housing cracked: Small cracks can sometimes be sealed temporarily with epoxy, but a cracked head should eventually be replaced.
- Line improperly seated: Recheck that line ends are in the eyelet slots and anchor notches.
- Too much line wound on spool: Remove excess line. Overpacking causes line to slip out during operation.
Testing and Breaking In the Trimmer
After reassembly, test the bump feed before full-use operation:
- Visual inspection: Hold the trimmer upside down and gently tap the head on your palm. You should see a tiny amount of line advance (typically 1/4″) with each bump. If no line advances, recheck winding direction and spool tension.
- Power-on test (low speed): Plug in or install the battery, then start the trimmer at low speed without engaging the cutting head near grass. Listen for unusual sounds and watch for line ejection. Turn off immediately if the head vibrates excessively or line tangles.
- First cutting session (outdoors): Use the trimmer outdoors on light grass for 2–3 minutes. Bump the head once or twice to test line advancement. If line advances smoothly and cuts normally, the job is complete.
- Check tension after initial use: Stop the trimmer and allow it to cool. Inspect the line length—it may have shortened as the spool settles. Tap the head once or twice to advance a bit more line if needed.
Expected behavior: New line should feel slightly stiff for the first few minutes of use. If the line remains tangled or refuses to advance after the test above, stop and review the winding direction and spool tension.
Frequently Asked Questions
Can I use any trimmer line in my bump feed head?
No. Always use the exact gauge (diameter) and material specified in your trimmer’s manual. Common gauges are 0.065″, 0.080″, and 0.095″. Using the wrong gauge causes the spool to jam, the bump feed to malfunction, or the line to break prematurely. If your manual is lost, contact the trimmer manufacturer with your model number or search online for specifications.
Why does my bump feed only advance line halfway?
The most common cause is line wound in the wrong direction. Unwrap the line completely and rewind it in the direction shown by the spool arrow (consult your manual if no arrow is visible). If line still doesn’t advance after rewinding, the spring mechanism may be weak or broken, and the head should be replaced.
Is it cheaper to replace the line or the entire bump feed head?
Replacing line is much cheaper—typically $3–8 for a spool of line versus $15–50 for a new head. Replace only the line unless the spring is broken, the spool is cracked, or the housing is damaged. If the head fails repeatedly after line replacement, then replacement is justified.
How often should I replace bump feed line?
Line life depends on usage, grass type, and obstacles. A typical spool lasts 1–3 seasons of regular use. If you trim weekly, you may need to wind a new spool or replace the head 2–3 times per year. Keep spare line on hand so you’re never without a trimmer when a spool runs out.
