In these cases, the spark plugs in the motorbike engine should be replaced with new ones:
The air-fuel ratio is too small, the mixture is too thick, fuel and oil can not be fully burned on the surface of the spark plug, or the use of poor quality oil, etc. will produce carbon; ignition advance angle is too large, or burst combustion and other abnormal combustion; spark plug skirt temperature is too low, that is, the thermal characteristics of the spark plug is cold, etc. will produce carbon.
Improper choice of oil can seriously affect the mixing and combustion of fuel. Excess C, Pb, Br, Cl and p in the fuel, C, Ca, S, Ba and Zn in the oil, as well as Fe, Si and Ai mixed in the mixture can affect the quality of the oil.
The spark plug is in contact with the gas. Generally speaking, the normal working temperature of the skirt is at 450℃-850℃, such as the temperature of the skirt is lower than 450℃ black carbon should be produced on the spark plug. Normal work of the spark plug on the carbon has self-cleaning (net) ability, but long-term work is not normal, carbon should not be removed, the spark plug self-cleaning ability will not be able to help.
In this case, you should first exclude the cause of the fault, replace the low heat value spark plug, or carefully scrape off the carbon, adjust the gap later. Serious carbon build-up will cause current leakage, weaken the spark jump, or even can not jump the fire, affecting the vehicle operation. Poor combustion will cause the vehicle to run weakly, or even not run at all.
Pure black carbon powder layer is a layer of dry or moist black carbon powder deposited on the surface of the spark plug. This layer of carbon powder can easily cause a short circuit in the head of the insulator, resulting in confused timing and poor low speed running. The engine is prone to stalling and bad startability, etc.
There is a shiny yellow layer on the insulating ceramic of the spark plug, which is caused by the chemical reaction of the lead compound in the fuel by heat. This layer can easily cause the engine to stall when adjusting the driving or climbing hills.
The lead compound fouling is caused by a sudden increase in throttle after a sustained low speed drive, which causes the fouling to melt and form a smooth surface after a sudden increase in cylinder temperature. This molten layer is a good conductor of electricity at high temperatures, thus making the spark plug out of action.
Because this cover layer is usually a very hard that is very difficult to scrape material, so must replace the new spark plug. In order to prevent this caking, you should use less lead or unleaded petrol.
The surface of the insulating ceramic and electrode of the spark plug is stained with red, green, white and brownish-yellow substances. This fault is relatively simple to remove, generally speaking, this kind of caking layer is not very thick, can be cleaned, scraped, re-adjust the gap can be used again.
The reason for this fault is the impurities of compounds contained in petrol and engine oil, or the incomplete combustion of tetraethyl lead in petrol, which gradually accumulates. At high temperature this impurity material membrane will become a conductive body, causing misfire, resulting in parking.
Due to acid corrosion, the surface of the electrode and insulation material is green, and the surface becomes rough and uneven, resulting in such a failure of the spark plug easy to cause high-speed, high-load engine stalling phenomenon.
Cause: Due to the influence of the gas temperature, combustion gases and lead compounds produce acidic substances that cause corrosion of the electrodes.