The use and maintenance of spark plugs
Published Time:
2021-09-17 12:06
Source:
The spark plug generates a spark across the gap between the center electrode and the side electrode; during this sparking process, the edges of the center electrode erode, forming a ring-like shape, gradually widening the gap and reducing ignition performance. In short, spark plugs are consumables that require regular maintenance, and new ones should be replaced every 3000-5000 km on a motorcycle. The function of a spark plug is to generate a breakdown spark between the side electrodes using electrical energy from the high-voltage wire. The material and shape of the center electrode and the side electrode, and the gap between the two electrodes are the most important factors affecting the spark generation of the spark plug, so a thorough understanding is necessary before maintenance.
1. Maintaining electrode cleanliness can maintain the ignition performance of the spark plug. During actual maintenance, the spark plug needs to be removed. Due to the different designs of various motorcycles, it is sometimes necessary to remove the fuel tank, especially for motorcycles produced in recent years, which have many fuel lines and wiring; therefore, these also need to be removed. During reassembly, be sure to confirm that the fuel lines and wiring are installed in their original positions.
Spark plugs are consumables, and regular maintenance can extend their lifespan. Furthermore, before the replacement period is reached, it is possible to prevent a decline in spark plug performance. As for maintaining lifespan, the first step is cleaning; remove any carbon deposits adhering to the electrodes or insulator. Since carbon deposits are conductive, when carbon deposits adhere to the spark plug, it will cause power leakage or weaken the spark; moreover, due to the influence of carbon deposits, the original cooling effect cannot be achieved; when cleaning the spark plug, to avoid damaging it, simply use a copper brush to clean it thoroughly.
2. Electrode shape repair and electrode gap adjustment. With increased use, the shape of the spark plug electrodes and their gap will change. Especially the center electrode, after continuous sparking, the surface will become rough and the edges will erode, making it difficult for the spark to jump, so it is necessary to use a file to reshape it, making its surface smooth and edges complete. Because of this, the gap between the electrodes will widen, and it needs to be measured with a feeler gauge and adjusted to the original specified gap. If you can perform the above regular maintenance, you can certainly keep the spark plug in good technical condition. 
3. Judging spark plug failure
Inspecting spark plugs is very important, and the key is to check the combustion color of the electrode. The combustion color of the electrode can determine the engine's operating condition.
(1) Check the electrode erosion color
The combustion color of the electrode can determine whether the engine is operating normally. The spark plug has a self-cleaning function within a certain operating temperature range; if the specified heat value spark plug is used, and the electrode is yellowish-brown, it indicates that the spark plug is operating within the normal temperature range; if the electrode turns cold white, it indicates excessive combustion.
Of course, the combustion condition of the spark plug is closely related to factors such as season, temperature, and driving conditions. If a cold white erosion color appears, a spark plug with a lower heat value than the specified one should be used; if carbon deposits appear, consider using a spark plug with a higher heat value. Of course, the mixture ratio should also be considered, and the best spark plug should be determined through adjustments.
If the spark plug turns black, it generally means that the combustion temperature is too low, and the reason is that the mixture ratio is too rich. There are many reasons for the mixture becoming richer; however, the main reason is that the air filter is dirty, leading to insufficient air intake and making the mixture richer. Therefore, the air filter should also be cleaned. If the spark plug turns white, this overheating combustion phenomenon is caused by the combustion temperature being too high. This is because the intake manifold or other parts of the intake system are loose or cracked, causing secondary air intake, or exhaust system leakage, making the mixture lean. Therefore, the carburetor or relevant parts of the exhaust pipe should be checked and repaired.
(2) Check whether the electrodes of each cylinder are completely burned
For multi-cylinder engines, except for special situations (such as different combustion or cooling conditions for different cylinders), the combustion color of the spark plugs in each cylinder should be basically the same. Therefore, by comparing the combustion color of the spark plugs in each cylinder, it can be determined whether the engine is running normally. When checking, the spark plugs of each cylinder must be removed and compared side by side.
(3) Check the electric spark
Before installing the spark plug, be sure to check the electric spark, that is, confirm the sparking situation of the spark plug. When the ignition system malfunctions (including the spark plug), checking the spark can determine which part has a problem and find the reason why the engine cannot start. If the used spark plug cannot produce a spark, another spark plug can be installed to check the spark situation. If the spark plug itself has a problem, of course, it will not produce a spark. If not, then there must be a problem with the high-voltage electricity before the spark plug. During operation, for spark plugs that have fallen to the ground, check whether the side electrode has been deformed. If this is the case, if other parts are not damaged, a screwdriver can be used to pry open the side electrode and restore it to its original state.
4. Matters needing attention when installing spark plugs
(1) When installing the spark plug, make sure to align the threads before screwing it in, and first screw it in by hand, then tighten it with a spark plug wrench. However, do not overtighten the spark plug when tightening it. Generally speaking, when screwing in a new spark plug, it should be tightened until the gasket begins to deform. Usually, beginners do not pay attention to this point. Therefore, the spark plug threads are often damaged when repairing spark plugs. Appropriate tightening force is important when tightening spark plugs.
(2) Since the high-voltage wire is inserted into the spark plug cap, if the spark plug is not problematic, and there is no spark when the high-voltage wire is tested, and no spark appears after connecting the spark plug, then the high-voltage wire is not properly inserted or the resistor in the spark plug cap is not tightened (or the resistor is broken). When the high-voltage wire is poorly connected, a small section of its head can be cut off and the surface rust cleaned, and then it can be inserted into the spark plug cap.
(3) During installation, check whether the high-voltage wire is aged and cracked, because aged high-voltage wires will leak electricity in rainy days or when splashed with water, affecting the ignition of the spark plug. Aged high-voltage wires should be replaced.
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