Spark and Ignition Problems

• A new spark plug often is a simple solution to many starting problems. If the spark is misfiring, you will have difficulty starting the trimmer and keeping it running. Remove the spark plug from the engine. Leave it connected to the rubber plug boot, and let the plug hang by a metal spot on the engine block. Slowly pull on the starter cord, and look for a spark. If you see a spark, you can move on. If there is no spark, replace the spark plug, and repeat the test. If you still can't see a spark, work back from the rubber plug, and check all the lines for damage or loose connections. Work back all the way to the starter, the magneto gap and the coil.
  
  

Air and Compression Problems

• Getting the right air and fuel mixture into the carburetor is crucial for the smooth operation of the engine. The intake and outtake air holes on trimmers can get clogged or dirty. Clean the air filter, fans and jets. Also, check the muffler and exhaust port for clogs and damage. Replace parts that are too dirty to clean.
  
  The piston drives the fuel from the carburetor into the chamber, and if there isn't the right amount of compression (about 90 psi for most two-cycle engines), the mixture of air and fuel will be inadequate. To check for compression, pull the trimmer off the ground by its starter cord. If the weight of the engine pulls out the line, the compression is low. If you can start the trimmer, try adjusting the carburetor to solve minor compression problems. If the compression problem persists, check the piston seals and the reed valve on the carburetor.
  
  

Fuel System Problems

• The most common problem for two-cycle engines is in the fuel system. Owners often store the trimmers improperly, with gas left in the tank or carburetor. When the gas dries off, it leaves a sticky deposit behind, which can wear out seals and other parts in the carburetor pretty quickly. To check the fuel system, depress the primer bulb to make sure it fills with gas. Disconnect the fuel line from the carburetor, and look for gas in the line. If in doubt, replace the fuel line and the fuel filter, which are inexpensive and solve a lot of fuel problems. If your trimmer starts, adjust the high-speed and low-speed screws on the carburetor. If the trimmer doesn't start, remove the carburetor, give it a thorough cleaning, and install a carburetor kit.