First of all, when the engine is running, there will be a pumping effect, at this time for the carburetor will produce a negative pressure, (similar to the principle of the needle) fuel in the carburetor through the main air and idle air is sucked out, because the air is very small, the pressure is relatively large, so the fuel is dispersed into a fog, through the intake channel and fresh high-speed air combined into a combustible mixture. In the plunger carburetor, in order to control the engine speed and power, must use a plunger up and down movement to control the carburetor throat of the mixture of gas, the piston valve oil needle is conical, stop the plunger down to the bottom of the time just blocked the oil channel, through the throttle line upward movement, the more open the channel, the more oil output and throat mixed gas volume.

In our idle condition, we need a very small mixture, at this time we can see that there is a semi-circular groove on the plunger, the idle screw is against this groove to slightly lift the plunger, the more you turn in, the more the plunger rises, the greater the oil output.

What is the function of the mixing ratio screw? There is a small air channel in the carburetor is not controlled by the plunger, the air channel is specially provided for idle, in this channel to add a screw as a stop valve, to control the amount of air in the air channel, so the screw will rotate to slowly block the air channel, turn out to increase the amount of air channel.

When the spark plug color is white

It indicates that the mixture is too thin, and the oil needle should be lowered by one grid and the mixing ratio should be increased. The color of spark plug is black, indicating that the mixture is too strong, and it should be adjusted by an oil needle to dilute the mixture. Another depends on the color of the spark plug, it should be about 5 kilometers at the speed of 40-60 kilometers per hour at 4000 to 6000, and the speed can not be reduced by grabbing the clutch and sliding halfway. Drive kilometers, immediately hang neutral, or grasp the clutch, turn off the engine to stop to see. (Note that each time the throttle needle height is adjusted, if the idle speed is unstable, the idle speed and mixture screws should be re-adjusted)

When the idle speed is unstable

The mixture screw and idle screw should be adjusted.

The method is: First screw the idle screw, in order to stabilize the ignition, and then adjust the mixture screw, clockwise for thick, reverse clock for thin, rotate around, pay attention to observe the idle speed until the highest point, and then adjust the idle screw to about 1500, and then rotate the idle screw around a small range, to the highest point of idle speed, and then the idle screw back to about 1500, so repeated several times, The idle speed will not change until the mixture screw is rotated left and right. The mixture should be adjusted after 3-5 minutes of hot driving.

What some people say is 1.5 circles of internal rotation 2 circles of external rotation, there is no need to know that the mixture is too thick or too thin will shine into the engine dead fire, you first turn inside until the dead fire, and then turn a little bit to the start of the fire, and then in a little bit of outward rotation, pay attention to the change in speed, you can listen, you can also see the tachometer, always twist to the maximum speed can be.

At high fuel consumption

The throttle needle should be adjusted, not the mixing ratio screw. One or two upward can effectively control fuel consumption, but there will be insufficient power, slow acceleration, high-speed meal and other phenomena, in my own experience, the low-speed power of the spark plug burned into brick red is really very general, for the car driving in the city at low speed acceleration is too important, so my car is turned to dark red. In this way, low and high speed will have sufficient power output, and in fact, as long as the spark plug is burned well, there is no need to care too much about fuel consumption, too thin mixture will be as the combustion speed of the engine fuel is reduced, the engine is overheating, and the output power is reduced.

Power difference high speed one meal at a time

It is obvious that the mixture is too thin, and the oil needle height should be adjusted according to method 1.

Starting difficulty, black smoke after starting

It is a sign that the mixture is too thick, and the idle mixture should be carefully adjusted in accordance with method 2 after the oil needle is raised one grid.

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