1. Common faults and troubleshooting methods of gasoline engines:

Small gasoline engines often have failures such as failure to start, difficulty in starting, or weakness after starting. The reasons for these failures are as follows:

1. Lack of fuel: Press the enrichment button on the float chamber, and no oil overflows. It may be because there is no oil in the tank or the oil circuit is blocked. Add enough mixed oil or clean the oil circuit.

2. The fuel does not meet the requirements: the proportion of the oil in the gasoline is too large to reduce the combustibility of the fuel. The gasoline should be mixed with the oil according to the required ratio.

3. The mixed gas is too thick: the mixed gas may be too thick due to insufficient opening of the choke valve or too high oil level in the float chamber. Correct adjustments should be made.

4. The mixture is too thin: the carburetor tempering, high-speed timing is easy to extinguish, all are the phenomenon of the mixture is too thin, the oil circuit is blocked, the oil level of the float chamber is too low, and the cylinder body leaks will cause the mixture to be too thin.

5. Insufficient compression force: Loose cylinder head screws, damaged cylinder gaskets, and wear of piston rings will all cause insufficient compression force of the cylinder.

6. Spark plug failure: Excessive carbon deposits in the spark plug, oil contamination on the electrode, incorrect electrode gap, and damage to the insulation will cause the spark plug to weaken or fail to generate sparks. Replace it.

7. Magneto fault: The contact gap of the magneto is too large, the contact is ablated, there is a short circuit in the low-voltage part, the high-voltage line is open, short-circuited, poor contact, and capacitor breakdown, which will cause the magneto to have no fire or the spark is very weak. Repair or replace with new parts according to specific conditions.

2. Agricultural motor

1. Selection of motor: When selecting a motor, consideration should be given to:

(1) Appropriate model: Generally, you can choose JO2 type for agricultural motors. That is, the enclosed three-phase squirrel cage motor.

(2) The choice of capacity: the capacity of the motor is too large, which will cause the phenomenon of "big horse-drawn trolley". It will cause waste and reduce the quality of power supply from the grid. The capacity of the motor is too small, and it becomes a "small horse-drawn cart" which may burn the motor. Generally, the capacity of the motor is selected to be 10% higher than the working power.

(3) Rotation speed selection: the selection of the motor should be based on the requirements of the working machine speed

Seek to select a motor with a suitable speed. Of course, it is not objective to require the speed of the motor to be exactly the same as that of the working machine. Within a certain range, the speed can be adjusted by changing the diameter of the pulley. Generally, it is more cost-effective to choose a high-speed motor. The high-speed motor has a simple structure and low manufacturing cost.

2. Selection of motor wire section: The diameter of the wire connecting the motor to the power supply should be selected according to the rated current of the motor. If the wire is too thin, it may cause the wire to overheat and burn out, or even cause a fire. If the wire is too thick, it will increase the cost and the installation will be laborious. Generally, the wire selected, the allowable safe current should be greater than the continuous working current of the motor, and there is enough margin.

3. Safety technology used by the motor:

(1) Inspection before use of the motor. In order to ensure the normal operation of the motor after it is put into use, before using the newly installed motor and the motor parked for a long time, it is necessary to check whether the circuit connection of each part is correct and good, and to measure whether the insulation of the motor winding is good. Turn the rotor by hand to see if the rotation is flexible. And try to start to see if it can be started and the direction of rotation meets the requirements. Run for a period of time to see if it runs normally, whether there are abnormal noises and strong vibrations. If there is any abnormality, power off and check immediately.

(2) Problems that should be paid attention to in the operation of the motor

① Strengthen the monitoring of the current and temperature rise of the motor. If the motor is faulty or overloaded for a long time, the current of the motor will increase and the temperature will rise sharply. Special attention should be paid.

②Pay attention to the change of power supply voltage. Too high or too low voltage is detrimental to the operation of the motor. Generally, the power supply voltage is not less than 5% of the rated value, not more than 10% of the rated value, and the difference of the three-phase voltage is not more than 5%.

③Pay attention to the sound of the motor. If there is abnormal noise or smell of burning, it should be shut down immediately for inspection.

④ Prevent the motor from running without phase (three phases of the power supply are broken and one phase). When the motor is running under phase loss, the current of the stator will increase sharply, the noise will also increase, and the motor will be burnt out in a short time.

(3) Safe use of electricity. If you don't pay attention to safe use of electricity, various accidents will occur. Such as fire, electric shock, equipment damage, etc. Therefore, knowledge of electricity use must be properly grasped to avoid accidents.

①Electric shock accident: Electric shock is caused by a relatively large current passing through the human body, and the degree of damage is determined by the size, path, and length of time of the current passing through the human body. An electric current of 80 milliamps passing through the human body will stop a person from breathing. If the current passes through the human body from hand to toe, the danger is greatest. Failure to disconnect from the power supply in time will increase the time of electric shock and increase the risk. Therefore, when wiring or performing maintenance, you must first cut off the power supply, and test to confirm that the equipment is not live before operating.

②Protection zero connection: In the power grid below 1000V and the neutral point is grounded, the protection zero connection should be adopted, that is, the shell of the motor and the neutral wire should be connected firmly. If one-phase or two-phase or even three-phase windings are damaged and short-circuited with the shell, the fuse of the short-circuit phase will be blown and the power supply will be cut off to avoid the risk of electric shock.