Whether you left gas in the tank over winter or it's just a few years old, one of the most common problems for a McCulloch chain saw is a bad or broken fuel line. Bad gas builds up a gummy layer inside the tube and this actually blocks the proper amount of fuel from flowing into the carburettor. The fuel line can break when it becomes hardened and brittle after several years of operation. Then, when you bump or jar the chainsaw a small hole can rip into the plastic tubing.
Get rid of any gas still left in the tank by pouring it out into an approved fuel container. Rinse the inside of the tank if it's dirty with a little bit of clean gasoline. Put the cover back on; shake it around and pour it back out into the fuel container.
Unscrew the carburettor cover's retaining screw, on top of the engine, with the flathead screwdriver. Lift the screw out and the cover off. Pull the air filter out of the air filter box.
Unscrew the 2 retaining screws holding the air filter box to the engine. Lift the screws out and pull the air filter box out. Locate the rubber or plastic fuel line on the elbow connector of the carburettor.
Pinch the fuel line with the needle-nosed pliers and unhook it from its elbow connector. Open the gas cap. Bend a hook into the thin metal wire. Dangle the hook into the fuel tank. Grab the end of the pre-filter and bring it towards the tank opening.
Grab and hold the pre-filter with the needle-nosed pliers. Remove the pre-filter from the end of the fuel line. Continue holding the fuel line with the metal hook. Pull the fuel line out of the tank with the pliers. Slide the metal hook out.
Cut off around six inches of new fuel tubing with the knife. Slice one end diagonally at about a 60-degree angle. Unbend the wire and slide it into the tubing. Push them both down into the tank.
Push the wire and tubing through the hole you pulled the original tubing from. Keep pushing forcefully until they both emerge from the hole near the carburettor. Slice the diagonal end off with the knife.
Push the new pre-filter's nozzle into the hollow tubing. Connect the fuel line to the elbow connector on the carburettor using your fingers, or the needle-nosed pliers if your fingers are too large. Reinstall the air filter box and two screws, the air filter and carburettor cover.