Can a motorcycle be removed from the spark plug cap? What harm?

Motorcycle spark plugs are an important part of the final ignition of a motorcycle engine ignition system. The role of the motorcycle spark plug is to jump the high voltage generated by the ignition coil at the end of the spark plug to a set gap, generate a strong electric spark, ignite the combustible mixture of the combustion chamber, and enable the engine to operate continuously and reliably. 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.

In short, in the ignition system, all the factors that can cause abnormal ignition and current fluctuations will eventually lead to early damage of the spark plug. During the inspection, if the insulation level of the electrical components is found to be reduced and the contact parts of the cable and the connecting wires of the whole vehicle are loose, the relevant faulty parts should be adjusted or replaced in time to avoid endless troubles.

Second, the fuel system

The combustible mixture is too rich, usually due to factors such as excessive oil level of the carburetor of the motorcycle, blockage of the main air volume of the carburetor, and serious blockage of the air filter element. If the carburetor is too rich, The engine will be hard to start, and sometimes there will be a "beep" sound. When you remove the spark plug, you will see that the electrode surface is wet by the fuel. At this time, the starting rod can be continuously stepped on, and if a large amount of oil mist is ejected in the spark plug hole, it can be judged that the mixture is excessively rich in the mixture. The following procedures can be used for maintenance:

1. First check the air filter for blockage. If the filter element is clogged with foreign matter, it will reduce the amount of air actually entering the engine cylinder. The air filter cover should be removed to remove the filter element and cleaned with a non-flammable detergent;

2. Check the oil level of the carburetor. Decompose the carburetor to see if the oil level is too high (subject to the technical parameters of each type of engine carburetor). After confirmation, the float chamber cover can be removed to take out the float needle valve. If it has been worn and damaged, it should be replaced;

3. Check if the air volume of the carburetor is blocked by foreign matter. If the carburetor oil level is normal, it may be that the carburetor's air volume hole is blocked by foreign matter. The carburetor cleaning agent can be removed and washed repeatedly until it is clean and fluent;

4. In addition, the carburetor on the seat car engine is generally equipped with an automatic rich valve device. If the automatic enrichment system malfunctions, it will also cause the combustible mixture to be too rich. During the inspection, connect the wire connector terminal of the automatic enrichment valve to the battery (voltage between 12V and 13V) to simulate the charging of the engine magneto. Wait for about 5 to 10 minutes, then connect the appropriate hollow hose to the fuel. On the incremental oil line, check with the mouth blowing gas. At this time, the fuel incremental oil path of the automatic rich valve is fully closed (ie, not ventilated).

Third, the lubrication system

If the exhaust pipe emits blue smoke during engine operation, it indicates that excessive oil enters the cylinder, which will cause a large amount of carbon deposit on the spark plug electrode or be wet by the oil and cannot jump. This phenomenon is commonly called engine oil, generally consists of the following Factor composition:

1. Two-stroke vehicles are generally separated and lubricated. It should be checked whether the flow rate of the oil pump is too large, and whether the worm oil seal and the check valve are invalid. If the engine with hybrid lubrication is mostly due to improper blending of gasoline and oil (normal steam and oil ratio should be: 40:1 ~ 60:1).

2. Most of the four-stroke vehicles use pressure-based lubrication. Piston rings and valve guide oil seals are the main means of lubricating oil:

a. When checking the air ring, the new car should be distinguished from the old one. If the new car should focus on whether the piston ring is opposite and the direction of the second piston ring is reversed, the oil ring assembly works well; the old car should be from the piston. Whether the ring and the cylinder tube are worn, or there are any abnormalities such as grooves and cylinders in the cylinder tube. When the piston ring side gap is too large, a large amount of oil will enter the cylinder due to the pumping action of the piston ring (normal air ring backlash) Generally, it is between 0.015 and 0.045 mm, and the use limit is 0.12 mm or more.

b. If the piston ring is in the normal state, the intake valve should be removed to check the back of the head for carbon deposits and wet grease. Serious wear of the valve and valve guide and hardening of the valve guide oil seal or excessive wear of the oil seal lip will cause the joint clearance to be too large and lose the sealing effect (the standard clearance of the valve and the valve guide is: 0.01 to 0.03 mm on the intake side, the exhaust side 0.03 to 005 mm). These two abnormal conditions will eventually cause the oil in the rocker arm chamber to be sucked into the cylinder along the valve shaft during the intake stroke to form a burnt oil phenomenon. In this case, the valve guide oil seal or valve should be replaced separately depending on its wear and tear.

c. If there is too much oil in the crankcase, or if the vent pipe is clogged, the pressure in the crankcase will rise and the balance will not be balanced. When the engine is inhaled, the oil will enter the combustion chamber to form the oil and the exhaust pipe will be exhausted. A thick blue smoke. To this end, oil should be added according to the instructions of each type of vehicle, with the upper limit of the oil scale, and the snorkel should be checked frequently to ensure its smooth flow.

d. If the engine exhaust pipe is blue or black smoke, it indicates that the spark plug is easily damaged due to various reasons. You can first analyze and search from the oil and circuit. After the black smoke fault is removed, check the piston ring, valve oil seal and other parts in order to eliminate the blue smoke fault.

In either case, as long as the oil enters the combustion chamber to participate in the combustion, a large amount of carbon deposits are generated in the combustion chamber and the spark plug, and the carbon deposit on the central electrode and the porcelain insulator generates a hot spot to ablate the spark plug; It will be conductive due to moisture, causing some or all of the high-voltage current to be grounded with the spark plug, resulting in weak or no fire, resulting in the engine not working properly.

It can be seen that the cause of the damage of the spark plug is multi-faceted. When analyzing and diagnosing the fault, the conscious mind should be kept. Follow the principle of simple, complicated, and easy to use. Generally, the external parts are inspected first, and then the internal parts are checked. Do not blindly disassemble the mechanism until the cause of the failure has been determined. When checking that a certain machine has not found a fault, it should be carefully assembled and restored to avoid the original fault and not cause the new fault.