Four-stroke motorcycle with big throttle, what's wrong with a cigarette?

Fast and convenient motorcycles enrich our life and expand our space, but motorcycles, like other motor vehicles, will bring endless troubles and unnecessary economic losses to riders if they are not properly maintained. If your car also emits colored smoke when driving on a flat road, she may have been seriously ill. But don't panic at this time, calm down and carefully observe the color of the exhaust. If the tail gas is colorless or slightly white, your car is absolutely healthy; If the exhaust is black, blue or thick white, you should think about whether there is something wrong with your car. If the exhaust gas is colorful or even full of smoke, it means that the engine is out of order. Find out the reason and repair it in time.

Black smoke from the exhaust pipe.

Black seems to be a depressing color. If it is not an early two-stroke motorcycle burning mixed oil (such as Happiness XF250, etc. ), there is only one reason why its "ass" emits black smoke: the mixture is too thick. That is to say, the gasoline component of the mixture in the cylinder exceeds the normal level, the gasoline is not completely burned in the combustion chamber, and carbon particles are precipitated and discharged with the exhaust gas.

Faults may come from the following aspects:

The air filter is blocked and the air intake is small. If the carburetor fails, such as the compensation air passage or idle air passage is blocked, the air intake is insufficient; The oil level in the floating chamber is too high, and some gasoline directly enters the cylinder without atomization, resulting in incomplete combustion; The main metering hole is seriously worn, which increases the fuel injection quantity of the main nozzle and causes incomplete combustion; The automatic valve to start heating is in the open position, and the thickening valve cannot be closed automatically, resulting in too high concentration of mixed gas. An EFI vehicle without carburetor may have a sensor that doesn't work properly and can't provide correct information to the gas distribution computer. In addition, the muffler is blocked by carbon deposit, the exhaust is not smooth, and the exhaust gas is trapped in the cylinder, which makes the fresh air burn insufficiently and emit black smoke.

If the above faults are not eliminated in time, it will lead to carbon deposition in the valve, affect the sealing of the combustion chamber, cause the engine power to drop, accelerate slowly and jam the car. Stop the vehicle immediately for maintenance, and troubleshoot in time.

First, check whether the air filter is blocked. If it is an air filter with paper filter element, it is generally better to replace the filter element. If it is a foam filter element, it should be cleaned with kerosene or incombustible cleaner. After drying, apply a small amount of lubricating oil on its surface (be careful not to apply too much, otherwise the air intake will be reduced). After cleaning the filter wall, put the filter element back.

Check the carburetor after confirming that there is nothing wrong with the air filter. For the plunger throttle carburetor, all holes and passages should be purged with compressed air to check whether the position of the main oil needle is appropriate. Generally speaking, the card should be located in the third slot (see figure 1). If the main oil needle is excessively worn, replace the floating needle valve and the needle seat at the same time (see Figure 2). If the main measuring hole is seriously worn (usually, its inner diameter becomes larger in the process of removing foreign matter with iron wire during maintenance), it should be replaced with a new main measuring hole. Check whether the height of the float is appropriate. The method is to turn the carburetor upside down, disassemble the float chamber to make the float tongue press the float needle valve, and measure the distance from the joint surface of the float chamber to the top of the float (that is, the height of the float), which should be consistent from left to right. For example, CG 125 is 18.5mm, JH70 is 20mm and CJ750 is 22mm. If it is not suitable, you can remove and adjust the float by pulling the float tongue with needle-nosed pliers.

For vehicles using vacuum diaphragm carburetor (such as Honda CH 125, HAMA 125, Suzuki AN 125, AN 150, etc.). ), you also need to check the automatic valve for starting heating. The specific method is as follows: connect the yellow lead for starting the heating valve to the positive electrode of the battery and the green lead to the negative electrode of the battery. After about 5 minutes, connect the polyethylene pipe to the fuel increment circuit and blow it with the mouth (see Figure 3). At this time, the fuel increase circuit is in a fully closed state, and there is no ventilation; If ventilation is convenient, it means that the automatic valve cannot close the fuel increment circuit, and the automatic valve that starts heating should be replaced.

The fuel consumption of EFI motorcycles is very low, and generally there will be no excessive mixture. Once this kind of fault occurs, ordinary maintenance personnel can't repair it. Only those trained professionals and manufacturers can repair it. Never disassemble it at will to avoid damaging the computer and causing greater losses.

Second, the tail gas emits blue smoke.

Blue is a melancholy color. If the tail gas of your car is blue, you will definitely feel unhappy, which means that the engine is burning oil. This is mainly due to the following reasons:

The gap between cylinder and piston or valve and valve guide is too large, and too much oil enters the cylinder, which mostly happens on motorcycles with long service life. Therefore, it is very important to check the gap between the two places regularly to prevent excessive wear. In addition, there is too much oil in the oil pan of a four-stroke vehicle, and a large amount of oil rushes into the cylinder during splash lubrication, which is also one of the reasons for blue smoke in exhaust.

When checking the clearance between the cylinder and the piston, we should focus on the wear of the piston and piston ring. When repairing, the diameter of the piston skirt should be measured, and if it reaches the wear limit, the piston should be replaced; Check and measure the clearance, elasticity and light leakage of the piston ring, and replace the piston ring if it is damaged, broken or reaches the limit. During installation, the chrome-plated ring is installed in the first ring groove, and the carbon steel ring is installed in the second ring groove. The lettering on the torus (such as T, N, R, UP) is upward, the inner chamfer is downward, and the ring mouth is far from the center of the pin hole, which is evenly staggered along the circumferential direction. There is no direction requirement for the rain wiper blade of the combined oil ring, but the opening of the wiper blade should be about 20mm away from the opening of the lining spring, and pay attention to the piston ring opening deviating from the direction of piston side pressure.

When checking the clearance between the valve and the valve guide, we should focus on the wear of the valve stem outer diameter and the valve guide inner diameter. When repairing, measure the diameter of the valve stem with an outside micrometer. If the limit is reached, replace the valve and pay attention to the grinding with the valve seat. Before measuring the valve guide, insert the reamer into the guide to remove deposits such as carbon deposit (see Figure 4). When the reamer enters or takes out, it should rotate to the right at the same time. If you rotate to the left or not, it will damage the inner surface of the catheter. Measure the inner diameter of the valve guide with an inner diameter dial indicator (see Figure 5). If it is larger than the maintenance limit size, replace the valve guide.

Valve guides are divided into flanged and flangeless types. The replacement steps of flanged valve guides are as follows:

1, heat the valve evenly to 100℃ ~ 150℃ (put it in the oven), and do not use gas burner for local heating to prevent the cylinder head from deforming;

2. Knock out the valve guide with a special tool (see Figure 6), taking care not to damage the joint surface of the cylinder head;

3. Apply lubricating oil to the new O-ring seal and install it on the valve guide;

4. Before the cylinder head is cooled, insert the valve guide from the camshaft side;

5. Ream the valve guide with a reamer (right hand as shown in Figure 7), and the reamer should not be skewed when reaming.

The replacement method of the flangeless valve guide is the same as the above method, except that before removing the valve guide, the height of the valve guide exposed from the cylinder head should be measured with a caliper and recorded (see Figure 8), so that the valve guide can be replaced according to the original height. In addition, loose valve guide or damaged cylinder gasket can also cause oil combustion. The valve guide and cylinder cover an interference fit. If they are loose, lubricating oil will leak into the exhaust duct (horizontal engine) or be sucked into the combustion chamber (vertical engine) for combustion. At this time, the valve guide should be replaced. When replacing, pay attention to heating the cylinder head, and then press it in gently. If the cylinder gasket next to the oil passage hole is broken, causing the oil to be sucked into the combustion chamber, just replace the cylinder gasket with a new one, and the fault can be eliminated.

There is also an extremely important point that readers must bear in mind: the direct cause of blue smoke from motorcycle exhaust is the excessive clearance between cylinder and piston or valve and valve guide. The direct cause of excessive clearance is long-term dry friction between cylinder and piston or between valve and valve guide, which leads to excessive wear. Therefore, selecting suitable lubricating oil is an important measure to prevent excessive engine wear and blue smoke from exhaust. Usually, you must use lubricating oil with satisfactory viscosity grade and lubricating oil grade (subject to the requirements of the on-board instruction manual). At present, 4T lubricating oil for motorcycles sold in China's market is divided into four grades: SD, SE, SF and SG from low to high. Generally, SE grade should be selected, SF grade is recommended, and SG grade (containing anti-wear and energy-saving agent, forming * * crystal compound on the surface of friction pair) can be used when conditions permit. It should be noted that the 4T lubricating oil for automobiles is slightly different from the lubricating oil for motorcycles (mainly in trace components), so it is best to choose major brand manufacturers with good reputation and good quality to produce 4T lubricating oil for motorcycles, such as Mobil Mobil, Shell Shell, Copton Compton, Prince Aide of Advani, Castrol, elf and Esso Esso.

Three kinds of waste gases emit white smoke.

White symbolizes purity, which almost everyone can affirm and accept. But when the waste gas is as white as milk, you should be more careful.

The thick white color in the waste gas is naturally caused by the high water content in the waste gas. There are two reasons: either you were cheated by the gas station and added too much water in the gasoline; Or the problem is that the motorcycle-waterway gasket is damaged, the cylinder liner is damaged, and cooling water enters the cylinder (for water-cooled engine). When gasoline is mixed with water, in addition to white smoke, there will be faults such as exhaust pipe injection and carburetor reverse injection, which is very harmful to the engine. The water-containing gasoline in the fuel tank and oil circuit should be removed in time. Water channel gasket of water-cooled engine should be replaced in time if damaged. If the cylinder liner is damaged, the cylinder should be repaired or replaced by professionals.