First screw the mixing ratio screw clockwise to the end, then take out two and a half turns, then start the engine to warm up, and then adjust the idle speed to 1500 rpm after the car warms up. If the idle speed is stable at this time, the fuel filler door is smooth. If it is not enough, fine-tune the mixture from half turn to one turn until the idle speed reaches the highest level, and then adjust the idle speed.
This adjustment should be made when the engine performance is normal and the carburetor is not blocked. If the engine or other parts of the car body affect the normal work, the mixture and idle speed can only be adjusted after being eliminated, otherwise the adjustment will be poor or inaccurate.