Ignition

• Ignition problems are common when the trimmer starts to age. The ignition system connects the "On/Off" switch to the starter, and the starter is connected to the flywheel and the flywheel key. Problems can arise throughout the system, but common problems are loose lead and ground ignition wires, a wire that's pre-grounded before it can spark and a faulty spark plug. You can use a voltmeter to check that the system is making a full circuit. Spark plugs should be replaced seasonally, at a minimum.
  
  

Compression

• Low compression results when too much air is getting into the carburetor, which causes an imbalance in the fuel mixture. Compression problems can be minor, including a dirty muffler or air filter, or more serious, like damage in the piston or crankshaft. The seals for both of these parts can also be worn out. You can use a compression gauge tool to make sure the engine can hold the proper amount of pressure.
  
  

Fuel Delivery

• Fuel problems are the most common problems experienced on these trimmers. If you've left gas in the tank or stored the tool improperly, you will notice a lot of gas delivery problems. Fuel filters and fuel lines should be replaced on regular basis and checked to make sure they aren't clogged. Dirty gas tanks or plugged gas caps can also cause gas-related problems.
  
  

Carburetor

• The carburetor is responsible for mixing and pumping the gas to the chamber for ignition. When the carburetor gets old, it can function improperly; when it gets dirty because of dried gas deposits, the deposits will choke the chamber and lead to improper firing. This can cause a wide variety of common indicators, like hard or erratic starts and poor running or stalling. Cleaning and servicing the carburetor can greatly extend its life. Installation of a simple carburetor kit can make the trimmer perform at its peak level again.
  
  

Trimmer Head

• Problems in the head will be easily noticed. Grass and weed clippings can jam up the internal head motor. Rocks or hard ground can also cause damage. The auto-feed springs under the bump knob can also get knocked loose or wear out. Rplacement parts are inexpensive and easy to find, and you should replace these parts as soon as they start going bad.