The owner of the car rides a single-cylinder four-stroke pedal 125 motorcycle (GY6 engine), saying that it has a feeling of pause at 60km. The speed is not high, and the maximum speed is always less than 65 yards.
After picking up the car, I briefly looked at it and drove about 24,000 km. No abnormality was initiated, so the car was completely inspected.
First check the ignition system, disassemble the spark plug, test the fire on the high-pressure damping cap, turn on the ignition switch, and the spark plug emits a strong spark, indicating that the ignition system is normal.
Then check the fuel system and see that the carburetor float chamber oil level is in the normal position. Open the cylinder head cover and rotate the crankshaft to the position at the end of the compression stroke. The two sides of the timing sprocket plane are substantially parallel to the plane on the cylinder head, indicating that the valve timing is correctly installed.
By the way, the valve clearance was checked and it was normal. After another test, I feel that the speed is very good at the beginning of the motorcycle, and the acceleration performance is basically no different from other normal vehicles. However, as long as the throttle is increased to the maximum speed, the vehicle will have a pause, and the exhaust pipe will not shoot. It should not be a problem with the ignition system.
In order to eliminate this troublesome fault, support the motorcycle, remove the side strip of the vehicle, pull the high-pressure damping from the spark plug, put on a new spark plug, and fire test about 5mm away from the spark plug on the car. The spark is very good.
Then increase the throttle test, the rear wheel of the motorcycle rotates rapidly, the engine speed keeps around 6000r/min, and continues to increase the throttle. Until the vehicle stops, there is no spark plug high-speed fire, indicating that the ignition system does not problem.
Then check the working performance of the vehicle's negative pressure switch: separately hang an oil pot (including oil pipe) to the carburetor inlet pipe, and then transport the negative pressure switch oil pipe through a rubber hose to an empty oil tank and pay attention to observe the oil. In the case, continue to increase the throttle test, the motorcycle still has a pause, but the negative pressure switch out of the oil pipe is normal.
It has been difficult to check until now. There is no problem with the ignition system, fuel system and valve timing, but the fault still exists. What is the reason?
I couldn't understand it, so I turned around and asked carefully when the owner's fault occurred. The owner said that it was replaced by a new air filter sent by someone else. Is it caused by air filtration?
Therefore, the original air filter assembly test of the same model was replaced. The feeling of pause at the original car speed of 60km disappeared immediately, and the maximum speed of the vehicle was close to 80km.
The reason for the analysis is that the user is cheap, and the air filter on other vehicles sent by others is installed. Since the air filter assembly does not match the technical parameters such as the intake air amount of the motorcycle engine, the air filter cavity is large. At high speeds, the amount of air is too large, causing the mixture to be too lean and causing poor combustion, resulting in a strange failure at high speed.
I would like to remind everyone that in the replacement of accessories must pay attention to the original matching performance of the accessories and motorcycle engines, to use good quality products, do not cause accidental failure due to cheap.
The faults in the car are not very common, and the maintenance personnel often ignore the inspection and do a lot of useless work. Many people are more arbitrarily used in the use of air filters. They think that as long as they are four-stroke engines, the installation dimensions are the same, no matter what. Models should be universal in air filters.