String

• The weed trimmer utilizes a spool of string to cut weeds down to size. As you use the trimmer, the string wears down and eventually you will run out of string. Replacing the string is a relatively simple process. Take care to unplug the unit from power or remove the spark plug from a gas unit, then follow the manufacturer's instructions to remove the spool cap and replace the line. Be aware that not all weed trimmer string is the same gauge and purchase string sized for your unit to ensure proper operation. Avoid downtime by keeping a spool of string on hand because it is hard to judge when you will need to replace the line.
  
  

Clean

• A clogged head can prevent your weed trimmer from operating properly and lead to uneven cutting. The area you are cutting may end up with more grass bent over than actually cut. After each usage, make sure the unit is unplugged, then clean grass and debris out from under the head before storing the unit. The best way to clean it is with an air compressor, and you can use a small putty knife to scrape away anything that the air leaves behind.
  
  

Filter

• Just like your car has an air filter that needs to be replaced periodically to ensure your car runs smoothly, your weed trimmer does, too. A clogged air filter can lead to a sputtering engine and eventually to the unit not starting at all. The filter is located on the carburetor and can typically be removed by removing a couple of knobs or nuts. Use the air compressor to blow the filter clean or purchase a new one.
  
  

Fuel

• Gas weed trimmers operate on a mixture of oil and gas. Follow the manufacturer's instructions regarding what type of oil to use and in what proportions. An improper mixture can lead to permanent motor damage and may even burn it out. Keep a special container of the mixture on hand, labeled for the weed trimmer to ensure you don't accidentally use it in the lawnmower instead.
  
  

Moisture

• It is important to wait until your lawn is dry before using a grass trimmer. Wet grass can lead to major buildup under the head of the unit, which can interfere with the string's path. The string can tangle into a knot and stop cutting. If this happens, you will have to stop, remove the debris and open the cap to the string to remove the tangle. You may even have to cut off a significant amount of string and rewind the remaining string before you get your trimmer back into working order. Be proactive and wait until the grass is dry before trimming.