Maintaining and Troubleshooting a Line Trimmer

by Nancy Ondra

Because line trimmers look so simple, it’s easy to forget they need routine maintenance just like your other lawn tools. Taking a few basic steps goes a long way toward keeping your trimmer ready for action.

Maintenance Checklist

Trimming under trees with a line trimmer

Hang a calendar in your garage or storage shed so you can easily keep track of when you use your line trimmer and for how long. Refer to the owner’s manual for recommended maintenance intervals. Here are typical guidelines.

At the beginning of each season, put fresh fuel into your gas-powered trimmer and check the cords on your electric trimmer. Replace the trimmer line, too. Old line can become brittle and break easily.

Before each use, fill the tank with a gas–oil mix of 40 parts unleaded gasoline to one part 2-cycle engine oil or whichever mix the owner’s manual for your gas-powered trimmer specifies. If you have an electric trimmer, check the cords. In either case, make sure you have plenty of replacement trimmer line on hand. If you’re using a blade, inspect it carefully and replace it if it’s bent or broken.

After each use, let your trimmer cool for several minutes (if it’s electric, unplug it) and then use a soft brush and cloth to scrub and wipe off grass clippings, dirt and other debris. Pay special attention to clearing the air intake vents on gasoline-powered trimmers. Also refill the trimmer head with line if it’s running low, so you won’t run out in the middle of your next trimming session. Last, inspect the trimmer for loose or damaged parts and repair them before you put the machine away.

After every 10 hours of use, clean your trimmer’s air filter to ensure efficient engine performance. Wash the filter in detergent and water, then rinse it and let it dry. Work a few drops of oil into the clean, dry filter if recommended for your trimmer, and then reinsert it.

After every 25 hours of use, remove and inspect the spark plug on your gas-powered trimmer. Clean or replace it if it’s dirty.

After every 40 hours, or at least once a year, inspect the entire trimmer for signs of wear or damage and make necessary replacements and repairs. Tighten loose bolts, nuts and screws. Replace the air filter and the spark plug.

Preparing for Storage

Before you put your trimmer away for the season, give it a thorough cleaning and lightly oil the metal surfaces to prevent rust.

You also need to empty or stabilize any fuel remaining in your trimmer. To get rid of the fuel, drain the tank into a US Department of Transportation-approved gas can, then start the engine and let the machine run until it stops on its own. To store your trimmer with a full tank, add a fuel stabilizer to the gasoline–oil mix in your gas can, shake it, and use the new mixture to top off your trimmer’s tank. Run the engine for about 5 minutes to circulate the treated fuel through the engine. If you already use a 2-cycle engine oil formulated with a stabilizer, you don’t need to add a separate stabilizer.

Troubleshooting Your Line Trimmer

Here are some common trimmer problems and solutions. For additional and more specific information, refer to the owner’s manual that came with your trimmer.

Line Breaks Frequently

Age, use and design can compromise the durability of your trimmer’s cutting line.

  • It’s normal for the line to wear down as you use it, but it may wear faster than you expect if you’re cutting tough or thick weeds, if you’re cutting against hard surfaces such as rocks and walls, or if the line is spinning too fast.
  • Old trimmer line can become brittle and prone to breaking.
  • Square and star-shaped lines tend to wear faster than round line.

If you find yourself replacing trimmer line frequently, make sure you’re using fresh round line and reduce the throttle speed on your trimmer. Also avoid crowding the trimmer head into the areas where you’re cutting; let the tip of the line do the work.

Cutting Line Doesn’t Advance

If you have to keep stopping your trimming because new line isn’t feeding out, you most likely have a problem with your trimmer head or spool of nylon line. Stop the engine and disconnect the spark plug on a gas-powered trimmer or unplug an electric trimmer to make sure the machine doesn’t turn on while you’re repairing it. Then take a close look at the trimmer head:

  • If the spool has emptied, replace it.
  • If the ports on the trimmer are clogged with grass or dirt, clean them out and wipe any debris from the line remaining on the spool.
  • If the cutting line is twisted, pull it off of the spool and rewind it carefully, making sure the loops don’t cross.
  • If the line has stuck to itself, or “welded,” due to the build up of heat, unwind the line, cut away the section that has melted or fused together, and then rewind the remaining line. If the problem keeps recurring, try using a higher-quality line labeled as “anti-weld” or “anti-fuse.” Those lines have higher melting temperatures.
  • If you see no line sticking out of the ports on the trimmer head, you may not have bump fed the line often enough. To correct for this, push the bump head down with one hand and pull out line with your other hand until you can touch the cutting guard with the tip of the line. You may have to remove the trimmer head cover and manually feed line through the port.

Cutting Line Advances Too Much

Each bump-feed and automatic-feed line trimmer has a small blade set into its guard that prevents the cutting line from getting too long. That blade eventually gets dull, and it can sometimes break off. If either of those things happens, the line feeds out farther than you expect, possibly slicing into fences, flowerbeds, trees or your shins. Fortunately, it’s usually a simple matter to replace a dull or broken cut-off blade.

Freelance writer Nancy Ondra gardens in Pennsylvania and blogs about her favorite plants at

Copyright 2010, Sears Brands, LLC. All Rights Reserved.

ShopYourWay Post Email icon

      • San Jose, CA

    Drain the gas out of the thing, between uses and run the engine till the tank is dry.

    Not only does the gas get stale in these machines, but, sometimes the plastic fuel lines are attacked by the ethanol mixed in with the gasoline, purchased from gas stations.

    Sears sells small cans of a 40:1 premixed fuel to oil, that does NOT contain ethanol, too.


The Community Blog is a place where you can discover countless posts about the things that interest you. So go ahead.

Explore. Comment. Repeat.