The primary and return fuel lines on a Ryobi gas trimmer are critical parts in the fuel delivery system, transferring gas to the carburettor. If these lines get clogged or kinked from excessive wear or bad gas, they will starve your carburettor of the proper fuel and air mixture. This can lead to burning out other parts, like the cylinder, piston seals and crankcase. Only use freshly mixed unleaded fuel and high quality, two-cycle engine oil to ensure the maximum performance from your engine.
Remove any old gas still in the tank. Pour it into an approved container. Start the trimmer and let it run out of gas.
Remove the four retaining screws holding the air filter/muffler cover in place. Take out the air filter and clean it in warm, soapy water. Let it dry before using it again.
Unscrew the primer bulb, next to the air filter cover, and gently pull out the plastic bulb and attached hose. If these are dirty, or cracked, replace them with new parts.
Use the screwdriver to remove the two carburettor mounting screws, which sit just above and below the air filter. Remove the screws and the washer. Pull off the choke lever and metal plate. If your Ryobi has them, remove the limiter caps on the carburettor.
Reach into the carburettor with the needle nosed pliers and unhook both the gas tank line and the return line from the carburettor's nozzles. Open the gas cap, reach into the tank with the pliers, and pull out the fuel filter and fuel line through the tank.
Use the screwdriver to remove the return line and tank mounting screw. Cut off about 7 inches of new fuel line for the gas line and about 4 inches for the return line. Angle one end on both lines at a 45-degree angle.
Insert the metal wire into the gas tank fuel line. Put a little engine oil on the outside of the fuel line and push it down through the tank's bottom hole. Keep pushing until the line is poking out near the carburettor.
Remove the metal wire from the first line and repeat process with the return line, except push the second line through the return line's hole on the side of the tank. Continue pushing until the line pokes out near the carburettor.
Snip off both of the angled ends. Pull them toward the carburettor, but don't connect them yet. Cut off any extra fuel line so there is about one to two inches above the tank's hole. Insert the nozzle of the new fuel filter into the fuel line.
Use the needle nosed pliers to connect them to the carburettor's nozzle again. Reinsert the primer bulb hose and primer bulb into their place. Screw them down to secure them in place. Reinstall the air filter and air filter/muffler cover.
If you can't reach the carburettor's nozzles on your model, you may also have to remove the carburettor to change the fuel line.