Motorcycle spark plug damage

The normal function of the motorcycle spark plug will directly affect the performance and power of the engine. Under normal circumstances, the service life of motorcycle spark plugs should be more than 10,000 kilometers. If some systems of the motorcycle engine are abnormal, the spark plug will be extremely wearable and damaged. The abnormal exhaust of the motorcycle with the spark plug often fails, which not only aggravates the air pollution, but also increases the fuel consumption and the economy becomes worse. In addition to the quality problems of the spark plug itself, changes in the technical conditions of the ignition system, the fuel system, the lubrication system, and the crankshaft linkage mechanism may affect the normal combustion of the engine, causing frequent damage to the spark plug. This paper intends to analyze the causes of spark plug damage, for the reference of users and maintenance personnel.


    First, the ignition system


    The spark plug ignites the combustible mixture in the cylinder, and must ensure a certain value of high pressure and an accurate and stable high-voltage electric field, otherwise it will cause irregular combustion and cause early damage of the spark plug. The main reasons are as follows:


    1. The motorcycle generator flywheel magnet is demagnetized. The generator magnetic field of most motorcycle engines is composed of two or more partial magnetic fields, and the magnetic force of each sub-magnetic field is different when the magnet is demagnetized, which causes the intensity of the adjacent magnetic field to be asymmetrical, and the current fluctuation caused. Larger. In addition, the degree of insulation of the ignition power supply coil is reduced, causing leakage or partial false short-circuit phenomenon, and the current fluctuation of the output is also large, so that the stability of establishing a high-voltage electric field is deteriorated.


    2. Motorcycle spark plug voltage is unstable. The false short circuit inside the ignition coil of the motorcycle and the electronic igniter will cause the primary ignition ground of the ignition coil, and the high voltage output is extremely unstable, so that the ignition voltage of the spark plug is out of control.


    3. The ignition wire of the motorcycle is in poor contact with the generator. The wire connection between the output end of the motorcycle generator and the input end of the ignition coil is loose, which may cause poor contact at the wire connection, causing "bounce" fluctuation of current conduction, and the turbulent current may seriously interfere with the normal ignition function of the spark plug.


    4. The temperature of the spark plug of the motorcycle is abnormal. In general, the spark plug heat value is set according to the different working conditions of the engine. When the engine is running at low speed and low load, the minimum temperature of the motorcycle spark plug should be higher than the self-cleaning temperature (referring to unleaded gasoline) about 500 ~ 580 ° C; when the engine is running at high speed and high load, the maximum temperature of the spark plug should be lower than the early fire temperature. 900 ° C; If you choose the lower first or second heat value specified in the instruction manual, the temperature of the spark plug will rise very high, and the heat can not be dissipated in time, causing abnormal combustion (that is, pre-ignition), which eventually leads to the spark plug. The electrode dissolves and is prematurely damaged. When replacing the motorcycle spark plug, it must be noted that the type, heat value and length of the spark plug should be consistent with the requirements in the instruction manual of the vehicle. If the models are inconsistent, or the thread is too long or too short, it will affect the ignition performance of the spark plug and shorten its service life.


    5. Motorcycle spark plug ignition is abnormal. If the air gap between the magneto and the charging coil core is too large (the normal air gap should be no less than 0.80mm), it will cause an abnormality when cutting the magnetic lines of force; in addition, the motorcycle flywheel will rub against the charging coil core, which will make it The coil temperature rises sharply and the insulation performance decreases. Both of these conditions can cause abnormal ignition and damage the spark plug.


    6. The ignition time is not accurate. The accurate ignition timing of the motorcycle is very important to ensure that the engine exerts its maximum function. It is often expressed by the "ignition advance angle" (commonly known as ignition timing). The electronic igniter is the most advanced ignition mode. The optimal ignition advance angle can be automatically changed with the engine speed to keep the ignition system of the engine in the best working condition, so there is no need to adjust the ignition timing.


    7, motorcycle spark plug failure:


    A, motorcycle spark plug sealing is poor. When the spark plug itself leaks, grayish black streaks often appear on the outer surface of the insulator. The spark plug of the motorcycle spark plug not only causes the spark plug to overheat, but also generates carbon deposits along the leaking portion, which reduces the insulation performance of the insulator, and causes the spark plug electrode to generate a hot ignition at the high temperature of the combustion chamber, thereby ablating the spark plug.


    B. Motorcycle spark plugs are loose. When the spark plug is not tightened or loosened, it will affect the heat dissipation of the spark plug through the cylinder head, causing the spark plug to overheat due to poor heat dissipation, resulting in ablation damage. Therefore, the spark plug should be fixed according to the specified tightening torque during maintenance (common torque: 10 to 12 N.m for M10 thread, 15 to 20 N.m for M12 thread, and 20 to 25 N.m for M14 thread).


    C. The insulator is broken. The breakdown of the insulator is usually caused by a strong collision or deflagration. In the spark plug flashover test, there is no spark between the electrodes, but there is a discharge sound of "beep" inside, and it can be judged that there is a break inside the insulator. The ignition of the spark plug after the insulation is broken may cause an abnormality, thereby causing hot ignition and destroying the performance of the spark plug, and should be replaced in time as found.


    D. If the spark plug cap is in poor contact with the spark plug, the current during ignition will suddenly rise, destroying the normal ignition function of the spark plug.


    8. The combustion of the combustible mixture is abnormal. Normally, when the crankshaft turns to a certain corner, the piston in the cylinder will move to a corresponding position. When the crankshaft is turned to the predetermined ignition angle, the piston also moves to the corresponding ignition position, thereby ensuring the synchronization of the crankshaft and the piston. If the crankshaft main bearing or the connecting rod end bearing is excessively worn (the radial clearance exceeds 0.10mm or more), the corresponding relationship between the crankshaft and the piston will be out of adjustment, resulting in improper ignition timing, thereby disturbing the synchronous relationship between the crankshaft and the piston. Causes abnormal combustion of the combustible mixture. In this case, the engine should be dismantled in time for a comprehensive inspection, and the relevant faulty parts should be replaced according to the wear condition. It must not be used to avoid causing damage to the entire engine to reduce unnecessary losses.