Ignition System Repairs

• 1). Unhook the rubber boot that's plugged onto the spark plug. Unscrew the spark plug, using the socket wrench and pull it out of the engine. Examine the rubber boot and wire for any damage or a loose connection. Discard the old spark plug.
  
  
• 2). Push the new spark plug, metal tip out, into the rubber boot. Using a gloved hand, hold it about 5 mm away from a metal spot on your engine. Crank on the starter cable a few times and look for a blue spark. If there's no spark, follow the ignition wires to the ignition switch, looking for damage, corrosion or a broken connection.
  
  
• 3). Unscrew the cover surrounding the ignition switch's wires. Unhook the ground wire, using your hand, from the ignition switch. Hold the boot and spark plug near the metal spot and use the same test. If a spark occurs, your ignition switch will need to be replaced.
  
  
• 4). Follow the lead ignition wires from the ignition switch back to the ignition module on the starter. Examine the wires for signs of corrosion, rust or broken connections. Change any bad wires for new parts.
  
  
• 5). Take the engine to a licensed small engine mechanic to test the entire ignition module, starter coil and wiring to make sure a complete circuit is being made.
  
  

Air and Compression Repairs

• 1). Unhook the air filter cover. Pull out the air filter from its housing. If it's made of padded foam, wash it in soapy water and let it dry before installing it. If it's made of felt, beat the filter against a hard surface, shaking off as much dust as possible. Swap out the air filter when it can't be cleaned.
  
  
• 2). Unscrew the muffler cover. Draw out the spark arrestor screen with the flat tip of the screwdriver. Wash this screen in the soapy water. Change the screen when the black carbon deposits cannot be removed.
  
  
• 3). Examine the exhaust port inside the muffler. Make sure it is free of carbon buildup and the engine can properly vent exhaust. Make sure the muffler isn't loose or coming unattached from the engine.
  
  
• 4). Disconnect and pull out the spark plug, if you haven't already. Insert the compression gauge's hose into the spark plug hole. Crank on the starter cord until the compression rises to 100 psi. Compression should remain above 90 psi.
  
  
• 5). Take the engine to a licensed small engine mechanic to inspect your cylinder, piston, piston rings, bore and crankshaft for air leakages. If air leaks are unfixable, replace the engine.
  
  

Gas System Repairs

• 1). Purge the tank and carburetor of any fuel by running the engine until it shuts off. If you can't start the engine, pour all remaining gas into an approved container. Rinse out the inside of the tank with a little soapy water. Scrub inside the tank's walls with the brush and rag. Make sure no dirt or debris is inside the tank.
  
  
• 2). Unhook both fuel lines from their elbow connectors on the carburetor. With the hook, grab the fuel filter inside the tank and pull out the filter and main fuel line. Pull out the return fuel line through the carburetor side or the bottom of the fuel tank, if it's accessible on your model. Change all of the fuel lines and fuel filter with new parts.
  
  
• 3). Open the choke to its half setting. Start the engine, if you can, and spray a one second blast of carburetor cleaner inside the open choke hole. Let the engine burn off all of the dirty deposits inside the carburetor. Wait until the smoke clears before using the trimmer.
  
  
• 4). Unscrew the carburetor from its mount on the engine and disassemble if the engine won't start. Clean all of the main carburetor parts, chambers and valves with a carburetor cleaner and brush. Swap out for new parts all of the filters, gaskets, seals and needle valve before rebuilding the carburetor.