1. When the mixture is too rich, gasoline leakage can be seen at the valve shaft; Insufficient engine power, difficult to accelerate; The exhaust emits black smoke and makes a "pop, pop" sound; Excessive carbon buildup on spark plugs; In severe cases, it will automatically shut down and cannot be started.
2. The reason for the malfunction of excessive mixture is usually found in the air filter and carburetor parts. The general reasons are:
(1) The air filter is too dirty and the filter screen is clogged
(2) The air damper is not fully opened
(3) Improper cleaning of the main measuring hole resulted in loss of the measuring hole and increased flow rate
(4) After the float ruptures, oil leaks or the triangular needle valve does not close tightly, causing the oil level in the float chamber to be too high
(5) The vacuum or mechanical fuel saving ball valve is not tightly closed, causing oil leakage and increasing the oil supply of the main pipe.
3. Fault diagnosis and troubleshooting
(1) Firstly, the oil level in the float chamber should be checked. In plain or hot areas, it is advisable to keep the oil level 1-1.5mm below the marking line. If the oil level is too high, adjustments can be made. Adjust to the specified standard, and if the oil level no longer changes after starting and works normally, it is considered as troubleshooting.
If the oil level cannot be adjusted to the standard position, the carburetor should be disassembled to check if there is oil in the float. If there is oil, it is a rupture of the float and should be welded or replaced; If the float is not broken and the installation position and shape have not changed, it is necessary to check whether the triangular needle valve is not tightly closed or stuck, and repair or replace it.
After repairing or replacing the float or triangular needle valve, reinstall and adjust the oil level, test the engine, and if the working condition is restored, it is considered as troubleshooting
(2) If the oil level inspection of the float chamber is normal, the air filter can be removed and the air damper can be checked to see if it is fully opened in the vertical position. If the air damper is stuck or cannot be fully opened, it should be repaired before testing
(3) The opening position of the air damper is normal without any jamming, and the test is normal without installing an air filter. Check if the air filter element is clogged due to being too dirty and should be cleaned or replaced with a new element.
(4) If all the above steps are normal, the carburetor should be disassembled for further inspection. First, check if the vacuum and mechanical fuel saving ball valves are tightly closed. If they are not tightly closed, consider the issue with the main measuring hole and make adjustments or replacements.
1. The phenomenon is that the engine idles unstably and is prone to stalling; The carburetor has a backfire phenomenon; Insufficient engine power makes it difficult to accelerate during operation; Pulling up the air damper will significantly or temporarily improve the situation.
2. The reason for the lean mixture in terms of its fuel system is essentially due to insufficient fuel supply and a low gasoline content in the mixture. Insufficient fuel supply can be divided into two situations: faults in the oil circuit outside the carburetor and faults in the oil circuit inside the carburetor.
The main reasons for insufficient fuel supply in the oil circuit outside the carburetor are:
(1) The gasoline filter is clogged.
(2) There is a blockage in the gasoline pipeline or a damaged oil pipe.
(3) The oil pipe joint is loose and leaking air.
The main reasons for insufficient fuel supply in the carburetor's internal oil circuit are:
(1) The carburetor inlet is blocked, which prevents the oil provided by the external oil circuit from entering the float chamber smoothly.
(2) The oil level in the float chamber is too low or the float is stuck.
(3) The triangular needle is stuck or other oil outlets are blocked.
(4) The main measuring hole is blocked or improperly adjusted.
In addition, air leakage from the intake manifold gasket or the carburetor base connection gasket can also cause the mixture to become too lean.
3. Fault diagnosis and troubleshooting
(1) Check the oil level height of the float chamber. If it meets the requirements, check if the main measuring hole is adjusted properly and if there is any blockage. If there is a malfunction, repair it.
(2) If the oil level in the float chamber is too low, the first step is to determine whether it is caused by the internal oil circuit of the carburetor or the external oil circuit of the carburetor, and then search for the faulty part in order. The steps are as follows:
① Remove the carburetor inlet pipe joint and observe the oil outlet of the oil pipe. If the oil outlet pressure is high and the flow rate is large, it is a malfunction in the carburetor's internal oil circuit.
Adjust the carburetor oil level; Disassemble the carburetor, check if the float is stuck, if the triangular needle valve is stuck, and if there is any blockage at the oil outlet. After the above steps are searched and repaired, the fault can be eliminated.
② Remove the carburetor inlet pipe joint and observe the oil outlet of the oil pipe. If the oil outlet pressure is low and the flow rate is small, it is a fault in the external oil circuit of the carburetor.
Then the oil pipes, fuel tank switches, and gasoline filter screens should be checked to troubleshoot.
(3) If there are no faults detected after following the above steps, then the intake manifold gasket or carburetor base connection gasket should be checked for air leakage.