Check the Fuel System

• When the fuel leaves the tank, it gets sucked up a small hose to the carburetor. At the carburetor, the fuel mixes with air and then gets sent on to the cylinder; excess fuel is expelled back into the tank through a second fuel hose. If the fuel is blocked or slowed at any stage, the engine will shut down. Dirty gas tanks, dirty fuel filters, blocked gas hoses and a dirty carburetor will cause these blockages. Drain the fuel tank and run the chainsaw until the fuel burns out. Take apart the entire fuel system, and replace both gas hoses, the fuel filter and clean the fuel tank and carburetor.
  
  

Check the Air System

• After the fuel system has been ruled out, check the quality and amount of air flowing in and out of the engine. Clean the air filter, which sits atop the carburetor, every 5 hours of use. If this filter is dirty, the engine will start but will slowly suffocate and shut down. Brush the filter box, and wash the filter in soapy water. Open the muffler's cover, and pull out the spark arrester screen. If the muffler is blocked, the engine will shut off. Wash the screen in the soapy water, and brush out the muffler.
  
  

Check the Spark Plug

• The spark plug sits on top of the cylinder and fires a high voltage spark in time with the fuel flow. If the spark plug is dirty, poorly gapped or corroded, the timing or the intensity of the spark will be wrong. Pull the rubber boot off the end of the plug. Use a 3/4-inch socket to take out the plug. Replace the plug with a Champion RCJ-7Y spark plug with an electrode gap of .025-inches. Fit the new spark plug in tightly and check the chainsaw again.
  
  

Adjust the Carburetor

• If, after checking all of the other functions, the chainsaw still won't stay running, adjust the carburetor. The carburetor uses three screws to regulate the inflow of gas into the carburetor at different engine speeds. If the low speed or idles speed screw is set too low, the engine will starve for gas at low speeds and shut off. Use a small screwdriver to slowly turn the low and idle speed screws in clockwise until the engine speeds up. Don't go past the limiter points as engine damage will occur.