First, open the fuel tank cover, unplug the fuel pipe (carburetor end), then unplug the vacuum pipe (engine end), and suck the vacuum pipe with your mouth until you find a lot of oil and dirt flowing out of the fuel pipe. At this time, bend the vacuum tube, clamp the bent part with a clip prepared in advance, and loosen the mouth, so that oil and dirt will drip continuously until it is sucked up (it is best to connect it with a plate below); Then pour new gasoline into the fuel tank and rinse the fuel tank (or put a towel tied with iron wire into the fuel tank to wipe it) until it is clean. One more thing, don't forget, take down the carburetor, clean it and put it back. Connect the unplugged tubing, then pour new gasoline into the fuel tank, screw on the fuel tank cover, and then connect the vacuum tube (the carburetor is full of oil at this time). Take away the dishes stained with dirty oil and dispose of the dirty oil properly. Turn on the ignition, start and stop the car!