1. air filter can not filter all dirty things
Throttle, it is the upper air filter, the next engine cylinder block, can be understood as the engine of the throat, or the previous coal stove above the wind door. The wind door opened large, the stove burned, the wind door opened small, the stove burned small.
The function of this throttle is to control the intake of the engine, which is in direct contact with the air.
Although there is this air filter in the filter, but the air filter can not be everything can be lost, or there is dust, dirt, will be through the throttle and throttle surface contact.
2. Oil vapor condensation adhesion caused by oil
Then the operating temperature of the engine is relatively high, the oil will produce oil steam.
In the case of engine idling or low speed, this oil vapor will carry these colloids in the fuel, condensing or pouring in, on this lower temperature throttle. We, is to take out a mineral water in the refrigerator, put in the room temperature, the edge of the dew, this is condensation.
This dewdrop of the throttle, which is a mixture of steam from this gasoline engine oil, then condenses up and becomes this thing.
3. Dust burning in mixed air turns black
Coupled with this kind of dust in the air, all kinds of steamed steamed roasted like Coke will be black off.
To put it simply, it is that when we cook, the cause of this oil smoke is similar.