The fuel line in a Stihl Trimmer needs to be replaced on a regular basis, usually every one to two seasons of work. These plastic hoses will often get gummed up from the impurities in the mixed fuel you use. This sticky residue will often suffocate the flow of gas by restricting the amount the sucks up into the carburettor. If you left gas in the trimmer over the winter, you can see how quickly this residue will choke off your engine. When you are having fuel supply problems the pickup body and the hose are the first things you should check and replace.
Unscrew the cap on the gas tank. Pour all remaining fuel into a clean gas container. Take out the screw holding the air filter cover in place using the Allen wrench. Lift away the filter cover.
Pull out the filter and clean it if necessary. Lift out the baffle, which is just underneath the air filter. Disconnect the tank's vent hose from the filter housing using your fingers.
Unscrew the filter housing's two bolts with the wrench. Slide the filter housing out. Remove the gasket underneath the filter housing. Underneath you will see the carburettor; to the right are two fuel hoses, the suction hose and the return hose.
Disconnect the fuel suction hose (lower hose) with the needle-nosed pliers, pulling it away from the carburettor's nozzle. Disconnect the suction hose (upper hose) by pulling it off the carburettor with the pliers.
Reach into the tank with the metal hook. Grab the fuel line and pickup body, pulling them slowly towards the tank opening. Grab and pull the pickup body off the suction hose. Pull both the suction hose and return hose out through the holes near the carburettor. Remember their holes.
Cut off two lengths of new fuel hose, about 7 to 8 inches long. Straighten the metal hook and insert it into the first length of hose. Push the hose through the main suction hose hole in the fuel tank until it emerges near the carburettor.
Trim off any excess line and push the hose all the way down onto the carburettor's nozzle. Install the new pre-filter onto the end of the hose in the gas tank.
Repeat the same process for the return hose, except push the hose and hook through the hole near the carburettor and into the tank. Pull the hose up with the hook and cut off any excess. Attach the end of the return hose to the outtake nozzle on the carburettor. Install the rest of the parts in reverse sequence.