Vacuum regulator The role of the vacuum regulator is to increase the ignition advance angle with the decrease in load. The inner cavity of the regulator is divided into left and right chambers by the diaphragm, the left chamber communicates with the atmosphere, and the right chamber communicates with the small holes on the wall of the mixing chamber of the carburetor. The spring 5 has a certain preload, trying to make the diaphragm arch to the left. One end of the pull rod is connected with the diaphragm, and the other end is sleeved on the pin shaft of the follower plate. When the gasoline engine is working at full load, the throttle valve is fully opened, the vacuum degree at the small hole 8 is not large, and the diaphragm is in the position of the largest bulge to the left. When the throttle valve is closed and the load of the gasoline engine decreases, the vacuum degree at the small hole 8 increases, and the pressure difference between the two ends of the diaphragm overcomes the force of the spring to move the center of the diaphragm a distance to the right, thereby driving the follower plate and distributor. The housing, together with the breaker contacts, rotates an angle opposite to the direction of rotation of the cam, increasing the spark advance angle. The smaller the throttle opening, the larger the ignition advance angle. When the throttle valve is close to fully closed, the small hole 8 is located above the throttle valve, the degree of vacuum is very small, and the adjusting device is in the position as shown in the figure, so as to facilitate the stability of the idle speed condition.