A string trimmer that is clogged with grass, has worn line, or a dull cut-off blade will work harder and cut less cleanly. Regular maintenance not only extends the life of the tool but also reduces safety risks, according to the Ohio State University Extension. Whether you own a battery-powered model like the one described in the Greenworks 24V manual or a gas trimmer, a few simple care steps can keep it running efficiently. If you’re still choosing a trimmer, see our string trimmer buying guide.
Why Maintenance Matters
The Ohio State University Extension states that proper maintenance will increase the life of the equipment and decrease the likelihood of safety risks due to equipment malfunction.
Safety First: Disconnect the Power
Both the Greenworks manual and the Ohio State University Extension emphasize removing the battery pack or shutting off the engine and disconnecting the spark plug wire before doing any work on the trimmer. The Greenworks manual specifically instructs you to remove the battery pack before cleaning, adjusting, or storing the machine. Ohio State adds that you should allow the engine to cool before refueling a gas model and never smoke around fuel sources.
Cleaning the Trimmer Head and Guard
The Greenworks manual recommends cleaning the machine after use with a moist cloth dipped in neutral detergent. Avoid aggressive detergents or solvents on plastic parts. Keep the trimmer head free of grass, leaves, or excessive grease, and keep the air vents clean to prevent overheating and motor or battery damage. Do not spray water onto the motor and electrical components. The University of Illinois Extension, in its mower maintenance guide, suggests using a leaf blower or air compressor to blow off clippings and debris, and scraping accumulated material with a putty knife, always after disconnecting the power. These practices apply to trimmers as well: after each use, wipe down the guard and head, and clear any wrapped grass from the motor shaft. The Greenworks troubleshooting section notes that grass winding around the motor shaft or trimmer head can cause the machine to stop.
Replacing Trimmer Line and Spool
The Greenworks manual provides detailed steps for replacing the spool and cutting line. Push the tabs on the sides of the trimmer head at the same time, then remove the spool cover and spool. Take off the coil protection and remove any remaining line. When installing new line, use only 0.065-inch (1.65 mm) nylon cutting line. Cut two pieces approximately 3 meters long, bend one end 1/4 inch (6.35 mm), and anchor the lines in the spool holes. Wind the cutting lines tightly around the spool in the direction indicated, place them in the guide slots, and do not wind beyond the edge of the spool. Reassemble by putting the spring in the spool housing, threading the line ends through the holes, and snapping the spool cover into position. For more on line types and diameters, see our trimmer line guide.
Adjusting the Cutting Diameter
The Greenworks manual notes that the trimmer is factory-set to a 12-inch (305 mm) cutting path, but you can adjust it to 10 inches (254 mm) by turning the cut-off blade 180 degrees. The choice involves a trade-off: a 10-inch setting gives greater runtime, while 12 inches covers a larger cutting area. The table below summarizes this.
| Cutting Diameter | Runtime | Cutting Area |
|---|---|---|
| 10 in. (254 mm) | Greater runtime | Smaller area per pass |
| 12 in. (305 mm) | Standard runtime | Larger area per pass |
To change the setting, remove the battery, unscrew the blade screws, rotate the cut-off blade 180°, and retighten the screws.
Caring for the Line Cut-Off Blade
The guard houses a small cut-off blade that automatically trims the line to a consistent length during operation, as described in the Greenworks manual. If the line no longer cuts cleanly, the blade may be dull. The troubleshooting section advises sharpening the cut-off blade with a file or replacing it. This simple step keeps the bump-feed system working correctly.
Battery Care and Storage
For battery-powered trimmers, the Greenworks manual says to remove the battery pack before storage and keep the machine in a cool, dry place away from corrosive agents such as garden chemicals and de-icing salts. If the battery or machine overheats, let it cool until normal function returns. Secure the trimmer during transport to prevent damage. Ohio State adds that for gas models, you should drain the fuel tank in a safe area and run the engine at idle until it stops before storing for extended periods. Always store equipment where children cannot access it.
Gas Engine Maintenance (If Applicable)
If you use a gas string trimmer, the small-engine care principles from the University of Illinois Extension’s mower maintenance guide apply. Air filters should be changed at least once per year to keep dust out of the engine. Fuel filters are typically replaced annually. Spark plugs need inspection: ensure contacts are clean and free of scoring, and replace them every two years, using the correct plug and gap specified in your owner’s manual. Avoid cross-threading when installing a spark plug. Ohio State also recommends maintaining proper oil levels and lubricating moving parts as per the operator’s manual. For a broader look at power source trade-offs, read our battery vs gas vs corded comparison.
Personal Protective Equipment
The Ohio State University Extension stresses that anyone operating a string trimmer should wear safety glasses with side shields or goggles, and a face shield for additional protection. Ear protection is needed because of high noise levels. Leather gloves protect hands from debris and sharp edges. Sturdy leather work boots or hard-soled shoes, ideally steel-toed, shield the feet. Wear long pants and a snug-fitting long-sleeved shirt to guard against flying clippings.
Routine Maintenance Schedule
The following table lists common maintenance tasks, how to perform them, and when, based on the Greenworks manual, Ohio State University Extension, and University of Illinois Extension guidance.
| Task | How to Do It | When |
|---|---|---|
| Clean trimmer head and guard | Wipe with a damp cloth and neutral detergent; clear grass from head and air vents; do not spray water on motor. | After each use |
| Inspect and sharpen cut-off blade | Sharpen with a file or replace if dull. | As needed |
| Replace trimmer line | Follow spool replacement steps; use 0.065 in. line for the Greenworks model; wind tightly. | When line wears short or breaks |
| Check and clean air filter (gas models) | Replace per manufacturer; at least once per year. | Annually |
| Change fuel filter (gas models) | Replace. | Annually |
| Inspect spark plug (gas models) | Clean, check gap, replace every two years. | Every two years |
| Drain fuel and run engine dry (gas models) | Drain tank, idle until engine stops. | Before extended storage |
| Remove battery for storage | Remove battery pack; store in cool, dry place. | Before storage |
| Inspect guards and safety features | Ensure deflector guards are in place and not overridden. | Before each use |
Always consult your owner’s manual for model-specific intervals. For a broader yard tool care overview, see our yard tool maintenance guide.
Frequently asked questions
How often should I replace the trimmer line?
The Greenworks manual indicates that you should advance the line whenever the engine sounds faster than normal or trimming efficiency drops. Replace the spool or rewind line when the line becomes too short to advance properly. There is no set time interval; it depends on usage and the type of vegetation you cut.
Can I use any diameter line in my trimmer?
No. The Greenworks 24V trimmer manual specifies only 0.065-inch (1.65 mm) nylon cutting line. Always check your owner’s manual for the correct line diameter for your model. Our trimmer line guide explains how diameter and shape affect performance.
Do I need to sharpen the cut-off blade?
According to the Greenworks manual, if the line is not cutting well, the cut-off blade may be dull. You can sharpen it with a file or replace it. This blade sits on the guard and trims the line to a consistent length.
For more on choosing and using string trimmers, visit our string trimmers category page.
