The spark plug is to let the spark splatter between the center electrode and the side electrode gap. During spark spraying, the corners of the center electrode will be peeled off to form a band-like circular pattern, and the gap will gradually expand and the ignition performance will be reduced. In short, spark plugs are consumables that must be regularly maintained, and spark plugs must be replaced every 3000-5000KM of motorcycles. The function of the spark plug is to generate a breakdown spark between the side electrodes with the electrical energy from the high voltage wire. The material and shape of the center electrode and the outer electrode, and the gap between the two electrodes are the most important parts that affect the spark plug to generate sparks, so it must be fully understood before maintenance.

1. Keeping the electrodes clean maintains the spark plug's firing performance

In actual maintenance, the spark plug needs to be disassembled. Due to the different shapes of various motorcycles, it is sometimes necessary to remove the fuel tank. Especially for motorcycles produced in recent years, the fuel tank is equipped with many fuel hoses and wiring, so they also need to be removed together. When assembling, be sure to confirm whether the fuel hose and wiring are assembled in the original location.

Spark plugs are consumables, and their service life can be extended with regular maintenance. In addition, the performance of the spark plug can be suppressed from deteriorating until the replacement period is reached. As for the method of maintaining life, the first is to clean up, first to remove the carbon deposits attached to the electrodes or insulators. Since carbon deposits are electrical conductors, when carbon deposits are attached to the spark plug, the leakage of electricity or the splashing spark will be weakened. Moreover, due to the influence of carbon deposition, the original cooling effect cannot be exerted. In order not to damage the spark plug when cleaning the spark plug, it can be completely cleaned by brushing with a copper brush.

2. Electrode shape refurbishment and electrode gap adjustment

The shape of the spark plug electrodes and their gaps change over time. Especially the center electrode, after continuous sparking, the surface will become rough and the corners will peel off. In order to prevent the sparks from splashing, it is necessary to use a file knife to shape it so that it shows the original smooth surface and complete corners. After the gap between the electrodes is enlarged, use a thickness gauge to measure and adjust to the original specified gap. If you can do the above regular maintenance, you can keep the spark plugs in good technical condition all the time.

3. Judgment of spark plug failure

Repairing the spark plug is a very important thing, and the key point is to check the combustion color of the electrode part. From the combustion color of the electrode, you can judge the operation of the engine.

1) Check the ablation color of the electrode

From the combustion color of the electrode, it can be judged whether the working state of the engine is normal. Spark plugs are self-cleaning within a certain operating temperature range. If a spark plug with a specified calorific value is used, and the electrode part turns yellow-brown, it means that the spark plug is working in the normal temperature range; if the electrode turns into a cool white color, it means that the combustion is excessive.

Of course, the combustion of the spark plug is closely related to factors such as season, temperature, and driving conditions. In the event of a cool white ablation color, a spark plug with one calorific value less than the specified spark plug should be used. If carbon deposits occur, consider using a spark plug with a larger calorific value. Of course, the problem of mixing ratio should also be considered at the same time.

If the spark plug turns black, generally speaking, the combustion temperature is too low, and the reason is that the mixture ratio of the air-fuel mixture is too rich. There are many reasons for the mixture to become thick; but the main reason is that the air filter is not clean, resulting in insufficient air intake and the mixture becomes thick. If the spark plug turns white, this overheating phenomenon is caused by the combustion temperature being too high. This is because the intake system such as the intake manifold is loose or cracked and the secondary air is sucked in, or the exhaust system leaks and the mixture becomes lean. Therefore, the relevant parts of the carburetor or exhaust pipe should be checked and repaired.

2) Check whether each cylinder electrode is completely burned

For multi-cylinder engines, except for special cases (such as combustion conditions or cooling conditions that are different due to cylinders), the combustion color and color of the spark plugs of each cylinder should be basically the same. Therefore, by comparing the color of the combustion of the spark plugs of each cylinder, it can be judged whether the engine is running normally. During the inspection, the spark plugs of each cylinder must be removed, and then side by side for comparison inspection.

3) Check the spark

Before assembling spark plugs. Be sure to check for sparks, i.e. to confirm that the spark plugs are flashing. When the ignition system fails (including the spark plug), after checking the spark, it can be determined which part is the problem, and the reason why the engine cannot be started can be found out. If the spark plug you are using cannot enter and exit the spark, you can install another spark plug and check the spark condition. If there is a problem with the spark plug itself, of course, the spark cannot enter and exit. If not, then there must be a problem with the high voltage before the spark plug. During operation, for the spark plug that has fallen on the ground, check whether the side electrode is deformed. If this happens, when other parts are not broken, use a screwdriver to pry the side electrode apart and restore it to its original state.

4. Matters needing attention when assembling spark plugs

1) When assembling the spark plug, it should be aligned with the thread and then screwed in, and first screwed in by hand, and then tightened with the spark plug wrench. However, do not use too much force when tightening the spark plug. Generally speaking, when screwing in a new spark plug, it is appropriate when its gasket begins to deform. Usually, beginners don't notice this, so often when the spark plug is repaired, the thread of the spark plug is damaged.

2) Since the high-voltage wire is inserted into the spark plug cap, if there is no problem with the spark plug, there is no spark in the high-voltage wire test, and no spark appears after connecting the spark plug, then the high-voltage wire is not plugged in properly or the resistance in the spark plug cap is not screwed well (or bad resistor). When the high-voltage line is in poor contact, you can cut off a small section of its head and clean the rust on the surface, and then insert it into the spark plug cap.

3) When assembling, also check whether the high-voltage line is aging and cracking, because the aging high-voltage line will leak electricity in rainy days or when it is splashed with water, which will affect the ignition of the spark plug. The aging high-voltage line should be replaced.