Check for Fuel

• 1). Dump out any old fuel and fill the trimmer with fresh gas and oil.
  
  
• 2). Push the primer bulb until it fills up with gas. If it doesn't fill, check the primer bulb and fuel line for any kinks, cracks or excessive deposits caked inside the line. Replace the fuel filter and fuel line if they are dirty, old or broken.
  
  
• 3). Open the choke to the half-open setting. Remove the air filter/muffler cover with the screwdriver. Spray starter fluid into the carburetor's neck and try starting the trimmer. If it still doesn't start, take it to a professional mechanic.
  
  

Check for Compression

• 1). Hold the trimmer up by its starter cord. If the cord pulls out rather than lifting the trimmer, your compression is low. Remove the air filter/muffler cover screws. Pull out the air filter and spark arrestor screen; clean both of these with the brush, detergent and warm water. Replace either one if it's too dirty to get clean.
  
  
• 2). Start the trimmer (if you can) and tune the idle speed screw on the carburetor. Tighten this screw clockwise 1/8 to ¼ turn or until the engine's idle speed is smooth and clean.
  
  
• 3). Check the exhaust port, bore, cylinder head and piston for any cracks or damages. If there's any damage you will need a replacement engine.
  
  
• 4). Check the reed valve, piston seals and camshaft for any damage. Replace these parts if they are worn out.
  
  

Check for Spark

• 1). Remove the spark plug boot attachment and unscrew the spark plug.
  
  
• 2). Put a new plug in the boot attachment. Ground the plug and boot wire to a metal point on the engine block.
  
  
• 3). Pull on the starter cord and check for a blue spark across the metal points. If there's no spark, try a different spark plug.
  
  
• 4). Work back from the plug to the ignition module, checking for any loose or damaged wires and connections. Check the coil, starter and magneto gap for damage. Replace any malfunctioning parts or take the trimmer to a professional mechanic to fix it for you.
  
  

Trimmer Head

• 1). Remove the bump knob from the outer spool ring. Turn counterclockwise to loosen. Pull off the cover and remove the inner reel and spring. Make sure the spring is engaging the inner reel.
  
  
• 2). Clean inside the head attachment, inner reel and spring. Check them all for damage or heavy wear. Replace any worn out parts.
  
  
• 3). Make sure the spring is engaging the bump knob to send out more line through the automatic feeder. If it isn't, replace the bump knob, the bump knob's locking nut or spool retainer cover.