Recently, I received a new Continent scooter. The owner said that his car started well, but if it slowed down and then accelerated on the way, there would be a feeling of poor refueling, and sometimes it would stall.
He had fixed it elsewhere, cleaned and adjusted the carburetor, but the glitches were sporadic.
After picking up the car, test the starting ability first, open the key and then press the start button, once failed to start, slightly increase the accelerator and try again, the car. After the engine starts to catch fire, idling operation is more stable, muffler exhaust sound is dull.
On the road test at the door, the motorcycle accelerated after the throttle, the speed dropped to 20 or 30, and then the door to speed up, and there was the problem described by the owner, the engine speed can not be improved smoothly, and it does not add the feeling of oil.
Back in the shop, turn off the fire and start checking. First remove the spark plug check, confirm that the spark plug electrode working clearance is normal, with thick black carbon deposit, has obvious insufficient combustion fault characteristics.
Insufficient engine cylinder pressure or faulty carburetor or improper adjustment will cause the combustible mixture to not burn fully, forming carbon deposits attached to the spark plug electrode. Therefore, we should start troubleshooting from the Angle of whether the engine cylinder pressure is normal and whether the carburetor is faulty.
Before installing the spark plug, plug the spark plug hole with your finger, start the engine, feel the cylinder pressure, and feel normal by experience. Of course, if you feel that your hand is not correct, you can plug in the cylinder pressure gauge for accurate detection at this time.
Exclude the reason of cylinder pressure, focus on the inspection of the oil supply system. When the carburetor is faulty or not adjusted, the combustible mixture will usually be concentrated, the motorcycle acceleration after the throttle, because the engine working speed is relatively high, the carburetor throttle quickly closed, the engine inlet vacuum degree increases, through the negative pressure hose acting on the carburetor break valve, the break valve diaphragm to overcome the spring pressure, the break valve closed.
According to the working principle of the vacuum carburetor, we know that the idle air channel of the carburetor has two measuring holes, one measuring hole has a small inner diameter and one measuring hole has a large inner diameter. When the air break valve is not working, the carburetor uses a larger inner diameter of the air measuring hole, which can enter more air to provide the engine with a thinner combustible mixture and reduce fuel consumption.
When the shut-off valve is working, the carburetor uses a small inner diameter air volume hole, which can reduce the incoming air to provide a thicker flammable mixture to the engine and prevent the flammable mixture from becoming too thin and causing the engine to stall.
At this time, the break valve is rapidly closed, and the idle channel of the carburetor is rapidly switched from the use of a large inner diameter measuring hole to the use of a small inner diameter measuring hole. The air entering the idle oil channel is sharply reduced. At the same time, affected by the vacuum degree in the inlet, the foam gasoline spewed from the idle jet hole increases, forming a particularly dense combustible mixture, which is not fully burned and makes the engine lose power.
When the refueling door accelerates again, because the carburetor throttle is slowly opened, too much gasoline into the intake port and cylinder before the concentration of the combustible mixture is still too strong, can not burn quickly, the speed can not be lifted, there is a feeling of refueling is not smooth, slow.
After the theoretical analysis, the carburetor was removed and carefully checked, and three faults were found after decomposition.
1. The working height of carburetor oil float is too low, resulting in too high oil-water level.
2. The number of set turns of mixed gas adjusting screw is too much, about 4~5 turns.
3: idle metering hole, main metering hole on the foam tube most of the small pores have been blocked by gum.
These three problems indicate that the carburetor has been adjusted. The previous repairman determined that the fault was caused by insufficient oil supply of the carburetor, which led to the failure of smooth refueling. The purpose of adjusting the carburetor was to increase the oil supply.
Now adjust the carburetor again.
One is to adjust the working height of the oil float, so that it meets the technical requirements, to ensure that the oil and water level maintain a normal height.
Second, unscrew the mixture adjusting screw, carefully remove the ring carbon deposit on the top working part, and then install the mixture adjusting screw, gently screw to the end, and then return the mixture adjusting screw two and a half turns.
Three is the use of fine wire to dreg the idle metering hole, the main metering hole on the small air hole foam pipe, the use of carburetor cleaning agent after washing, loaded and loaded back to the carburetor.
After installation, prepare for the test run. After opening the key, press the start button, and the engine will trigger and start the fire smoothly. After the engine fire idle speed is higher, the muffler exhaust sound is not dull. After fully warming the machine, turn the throttle adjusting screw, adjust the idle speed of the engine, make it meet the technical requirements.
Driving the motorcycle road test test, the motorcycle ran normally, driving after slowing down and then accelerated, the throttle response is good, the feeling of not adding oil disappeared. The owner felt very satisfied after the test ride.