If it is confirmed by inspection that the engine is in good acceleration condition, it indicates that the combustible mixture provided by the carburetor to the engine is too thin or too small, and the combustible mixture cannot ignite reliably, leading to the failure of engine acceleration.
If the test confirms a deterioration in engine acceleration, it indicates that the carburetor is supplying the engine with too much or too much combustible mixture. The fuel mixture did not burn sufficiently, causing the engine to fail to accelerate.
Air cleaner filter almost all local or blockage, the carburetor of inspiratory resistance increases, the carburetor mixture indoor negative pressure increased, foamy gasoline will be from the main nozzle jet, mixed with a small amount of air atomization, mixture, formed a strong mixture can not be too thick high voltage ignition electric spark ignited in a reliable way, even if barely ignited by high voltage electric spark ignition, combustible mixture can not completely burn adequately, can also lead to engine can't accelerate the failure.
At this point, you can disconnect air filter with carburetor, make the air without air filter cartridge, directly into the carburetor, in order to reduce the mixture concentration, then the engine acceleration test, if it is the engine speed to normal, this suggests that the air cleaner element has partially blocked or is almost completely blocked, led to the engine can't accelerate the failure.
If the engine is still unable to accelerate, this indicates that the engine can not accelerate the fault has nothing to do with the air filter, which also rules out the possibility that the engine can not accelerate the fault because the air filter is not working properly.
When disconnect the air filter from the carburetor for inspection, also pay attention to the carburetor inlet whether there is a reverse jet flow and the severity. This is one of the causes of the failure.
Carburetor has anti jet flow, reverse jet flow can contain a large number of small gasoline particles, this is because the jet flow through the carburetor mixing chamber, will be like the normal work of the carburetor, the carburetor mixture indoor formed strong pressure difference, forced foamy gasoline from the main nozzle jet, forming fog gasoline mixed with air flow.
When the mixed air is again drawn into the carburetor, the main nozzle of the carburetor again spurts foam-like gasoline and mixes with the mixed air, forming an excessively thick combustible mixture that is extremely difficult to ignite by the high-pressure ignition spark, leading to the failure of engine acceleration.
Muffler internal local blockage or almost all blockage, will increase the muffler exhaust resistance, the pressure inside the muffler will be unusually high, leading to poor engine exhaust, which is also one of the root causes of poor acceleration.
At this point, not only can the exhaust gas in the engine cylinder not be discharged in time, but also when the engine inlet valve opens, the residual exhaust gas pressure in the engine cylinder is higher than the engine inlet pressure, under the action of pressure difference, the residual exhaust gas will come out from the carburetor inlet, forming the mixed air flow of oil and gas.