How to maintain the motorcycle fuel system?

(1) Inspection and maintenance of throttle valve

Turn the throttle handle to check whether the return position is good. If it gets stuck or can't go back, it needs maintenance.

① Remove the reflector.

② Remove the oiler seat, and take off the throttle line and oiler.

③ Add a little lubricating oil to the accelerator cable and apply a little grease to the oiler.

(4) put it back in the opposite order.

Note: the throttle cable should be cleaned and lubricated every 2000 kilometers.

(2) Adjust the free stroke of the throttle knob.

If the adjustment still fails to meet the requirements, the adjustment solenoid valve at the upper end of carburetor should be adjusted. When adjusting, first open the dust cover and rotate the adjusting solenoid valve until the free stroke of the throttle knob is 2 ~ 6mm, then pull down the dust cover and cover the adjusting screw.

For a two-stroke engine, after adjusting the free stroke of the throttle handle, check whether the mark on the control rod of the oil pump is aligned with the mark on the oil pump body when the throttle knob is fully opened (the error is normal within 65438±0mm). If the marks are not aligned, loosen the lock nut on the oil pump control cable, adjust the adjusting nut until the marks are aligned, and then tighten the lock nut, as shown in Figure 3-4.

Figure 3-4 Adjust the free stroke of the throttle knob

(3) Clean the oil tank

The oil tank is formed by stamping and roll welding of thin steel plate. In order to prevent the corrosion of gasoline, the inner surface of the fuel tank is sandblasted and phosphatized or sintered with enamel. The top surface of the oil tank is provided with an oil filler, and the oil filler is provided with an oil tank cover with a rubber band. A small vent hole is drilled on the tank cover to keep the inside of the tank connected with the atmosphere.

Clean the fuel tank every 5000 ~ 6000 kilometers of the motorcycle. When cleaning the fuel tank, pay attention to the following items:

① When cleaning the fuel tank, the fuel tank must be removed. First, unscrew the fixing bolts of the fuel tank, unload the fuel tank, then install a small amount of gasoline, and move the fuel tank up and down for impact cleaning. If the inner wall of the oil tank has rusted, you can put a small amount of iron sand in it and repeatedly impact it, and finally rinse it with gasoline several times until it is clean.

(2) There is oil leakage and oil leakage in the fuel tank, which can be repaired by gas welding or tin welding. Before welding repair, wash the oil tank with boiling water for many times, dry it, and then weld repair. Otherwise, the high temperature of welding repair will make the remaining gasoline in the fuel tank burn, which will lead to the explosion of the fuel tank and cause an accident.

(3) The hole on the tank cover should be kept clear, and if there is any blockage, it should be dredged. The rubber gasket on the tank cover should be kept intact. If it is damaged, it can be prepared with oil-resistant rubber.

Figure 3-5 Check the fuel tank switch

(4) Check the fuel tank switch

Unplug the negative pressure pipe on the fuel delivery pipe and the intake pipe of the carburetor, and inhale the gas through the mouth, thus generating negative pressure on the vacuum diaphragm in the fuel switch. If there is oil flowing out of the oil pipeline, it will not flow out even if the oil absorption is stopped, indicating that the fuel switch is working normally; If the oil still does not flow out when inhaled, it means that there is blockage or damage inside, and it should be replaced with a new one, as shown in Figure 3-5.

(5) Clean the fuel tank switch

There is a filter screen at the joint between the bottom of the oil tank and the switch, which can filter out the dust and impurities in the oil tank. Over time, the filter screen will be blocked by deposits in gasoline. Below the filter screen is the oil tank switch, which is equipped with a filter element to filter out fine dust and impurities. When the gasoline circulation is not smooth, it is necessary to clean the filter screen and filter element.

When cleaning, first unplug the oil pipe from the oil tank switch, put a container under it and turn the switch to the ON position. At this time, the gasoline circulation is not smooth, indicating that the filter screen or switch is blocked. Then clamp the stud above the switch with a wrench, unscrew the bottom cover of the switch with a wrench, and remove the bottom cover together with the filter element and O-ring seal. Remove the silt and sediment accumulated in the removed switch cover and clean it with gasoline. When cleaning sealing ring and filter element, be careful not to bend or damage them.

After cleaning the switch bottom cover, if it is still blocked, it is necessary to remove the oil tank switch and clean the filter screen in the oil tank. When removing the fuel tank switch, you must turn the switch to RES position so that all the gasoline in the fuel tank can be discharged. Wash the dirt off the filter screen with a brush. Never wipe the filter screen with cotton yarn to avoid blocking the carburetor. After the filter screen and fuel tank switch in the fuel tank are cleaned, assemble them in the reverse order of disassembly.

Figure 3-6 Check the output of gasoline pump

(6) Check the gasoline pump

Start the engine at idle speed, remove the oil pipe, let the gasoline flow for 5s, and then start to measure the gasoline flow within 10s. If it is greater than 28mL, it is normal. If the amount of oil is insufficient or there is no gasoline flowing out, check whether the oil circuit, negative pressure pipe and fuel filter are abnormal. If yes, please replace it with a new one. Otherwise, the gasoline pump is damaged and should be replaced, as shown in Figure 3-6.

When the oil inlet pipe is removed or the lubricating oil is used up, air can easily enter the oil inlet pipe. The existence of air will inevitably lead to the interruption of gasoline engine lubricating oil supply and damage to the engine, which must be paid great attention to. Both the oil inlet pipe and the oil outlet pipe of the oil pump are transparent plastic pipes, so it is clear at a glance whether there is air in the pipes. If air is found in the pipeline, it should be discharged immediately. The sequence of exhaust is as follows: first, check whether the reserve of gasoline engine lubricating oil in the fuel tank meets the specified requirements, and if it is insufficient, it should be supplemented. Loosen the deflation screw on the oil pump again, and then completely pull out the oil pump control wire rope, as shown in Figure 3-7. At this time, the lubricating oil and air will be continuously discharged from the bleeding screw. Carefully observe the movement of air bubbles in the oil inlet pipe. When the pipeline is completely filled with lubricating oil, it means that the air has been exhausted. At this time, quickly tighten the deflation screw and finally wipe off the oil stain.

Figure 3-7 Gasoline Pump Bleeding

(7) Maintenance of carburetor

Regular maintenance of carburetor can not only prolong the service life of carburetor, but also reduce the failure frequency of engine, improve the service performance of engine and prolong the service life of the whole machine. Therefore, all motorcycle operating instructions clearly stipulate that the carburetor should be thoroughly inspected, cleaned or adjusted after a certain period of time or mileage, that is, regular maintenance. Idle speed of motorcycle should be adjusted once every 1000km; Clean the carburetor every 4000 kilometers.

In addition to strict regular maintenance, it is also very important to carry out routine maintenance on the carburetor regularly to prevent failure. The routine maintenance of carburetor shall generally include the following contents:

① Clean the fuel tank and the fuel tank switch frequently, and filter it strictly when refueling to prevent foreign matters such as dust and impurities from leaking in, so as to keep the gasoline clean and prevent the carburetor oil circuit from being blocked, resulting in insufficient oil supply or even fuel cut-off, which makes the engine unable to work normally.

(2) Check the cleaning air filter frequently, and check whether the connection between the carburetor and the air filter is loose, so that unfiltered air enters the carburetor, blocking the pores of the carburetor, resulting in excessive mixed gas, unstable idle speed, increased fuel consumption and other failures.

(3) Keep the nozzle of the ventilation pipe in the float chamber clean at all times, so as to avoid the blockage of air holes and pipes, which makes it difficult to suck out the gasoline in the float chamber, resulting in the failure of insufficient oil supply and too thin mixed gas.

(4) Always check whether the joint between carburetor and intake pipe leaks, so as to prevent the fastening screw of carburetor from loosening due to earthquake, resulting in air leakage and difficult starting. In addition, always check whether the screws of the float chamber and the mixing chamber cover are loose.

⑤ Regularly remove the silt, grease and other dirt at the choke turret and throttle turret to prevent these dirt from accumulating at the turret, causing the choke shaft and throttle shaft to get stuck and damaging the operating mechanism.

(8) carburetor idle speed adjustment When idling adjustment, the ignition system and oil supply system of the engine must be normal. The engine can only be adjusted after 5 minutes of warm-up. Before adjustment, the choke valve must be opened and the air filter installed.

Put the transmission in neutral and support the main parking frame; Fully warm up the engine, gently screw the idle air adjustment screw to the end, and adjust the throttle stop screw to keep the engine idle. Then, loosen the idle air conditioning screw and confirm the number of return turns of the idle air conditioning screw at the position where the engine speed starts to rise and the position where it can no longer rise. The middle of these two points is the proper position of the idle air conditioning screw, as shown in Figure 3-8.

Figure 3-8 Adjusting carburetor idle speed

When the idle air adjusting screw is screwed in clockwise, the air volume decreases and the air volume increases when it returns. Therefore, when the vehicle speed needs to be increased, the recycling amount is less, and conversely, when the fuel consumption is given priority, the recycling amount is more.

(9) Synchronous adjustment of carburetor

After the engine is fully warmed up, turn off the engine, unscrew the negative pressure measuring screw on the intake pipe, and connect the negative pressure gauge to the intake pipe of each cylinder. Then, start the engine and adjust the idle speed to a specified value; Based on the negative air pressure of the reference carburetor (unadjusted), turn the adjusting screw with a screwdriver to adjust the difference between the negative air pressure of other carburetor and the negative air pressure of the reference carburetor to below the specified value. Then quickly turn the throttle knob several times to make sure the adjustment is stable, as shown in Figure 3-9.

Figure 3-9 carburetor synchronous adjustment method

(10) High speed adjustment in carburetor

The adjustment of medium speed and high speed should be carried out according to various phenomena in motorcycle running.

When the motorcycle is running at medium and high speed, it is characterized by too rich or too thin combustible mixture. There are two adjustment methods:

Figure 3- 10 Adjust the float position

One is to adjust the height of the throttle needle. If the combustible mixture is too thick, unscrew the cover of the mixing chamber, take out the throttle needle, and clamp the locking piece of the throttle needle into the last groove. If the combustible mixture is too thin, the locking piece of the throttle needle should be clamped into the next groove.

Another method is to adjust the position of the float. Remove the float chamber, turn the carburetor upside down, as shown in Figure 3- 10, and gradually lower the float until the float tongue touches the upper part of the float needle. Measure the distance between the joint surface of the float chamber and the top of the float. If it is less than (22.5 1) mm, it means that the oil level is too high and the combustible mixture is too rich. If it is greater than (22.5 1) mm, the combustible mixture is too thin. Take out the float, first iron the top of the float with a red-hot iron bar, then gently bend the float tongue by hand, change the radian of the float tongue, and adjust the distance within the range of (22.51) mm. Different motorcycles have different heights of floats. Please refer to the maintenance manual for details.

Under different working conditions of the engine, different parts of the carburetor should be adjusted when the mixture is too rich or too thin, as shown in Table 3-4. See Table 3-5 for several adjustment methods of motorcycle fuel supply system.

Table 3-4 Adjustment of Carburetor

Table 3-5 Adjustment Methods of Several Motorcycle Fuel Supply Systems

Table 3-5 Adjustment Methods of Several Motorcycle Fuel Supply Systems (Continued)-1