1. Do not press the cylinder liner with the cylinder head.

Some agricultural machinery operators directly install the cylinder cover without installing the cylinder gasket, and press the cylinder cover by tightening the cylinder cover bolts. In this way, when the cylinder liner is pressed in place, all the pressure of the cylinder head acts on the shoulder of the cylinder liner which is only about 3 mm, which will lead to the fracture of the cylinder liner. The correct installation method is: put the board on the upper end of the cylinder sleeve, and tap the board with a hammer until the cylinder sleeve is in place.

2. Do not flush the gasoline tank with compressed air.

Before repairing the gasoline tank, the gasoline in the tank must be cleaned. Some repairmen use compressed air to flush the oil tank. Because the opening of the oil tank is small, gasoline molecules in the tank will produce sparks due to strong collision, which is easy to cause explosion and cause personal casualties. The gasoline tank should be cleaned with cleaning agent.

3. Do not use spring pads instead of locking plates.

After the connecting bolts between the driven drum hub and the driven drum of the steering clutch of Dongfanghong-75 tractor are tightened, they are locked with locking plates. For the convenience of disassembly, some operators replace the locking plate with spring pad, and some add a flat washer. Because the washer is thicker than the lock plate, the top of the connecting bolt rubs against the left and right side walls of the rear axle housing after assembly, and the tractor constantly pulls the control lever during operation, the rear axle shaft moves axially, so a deep annular groove is worn out at the corresponding positions on both sides of the housing, which greatly reduces the strength of the housing. Once the tractor is overloaded, the rear axle housing is easy to break from the ring groove.

4. Do not prepare oil drain plug at will.

The oil drain plug on the oil pan is made of magnetic material, which can effectively absorb iron filings in the engine oil and reduce machine wear. It can not be made of ordinary steel or replaced by other plugs.

5. Do not heat the piston with an open flame.

When some maintenance personnel replace the piston, in order to assemble the piston pin smoothly, they pour some diesel oil into the piston, plug some rags, and then ignite and heat the piston directly. The disadvantages are as follows: first, the piston is easy to deform due to uneven heating; second, the rags are not easy to remove after burning ash, which will accelerate the wear of cylinder liner piston ring; third, it takes a long time to put out the fire and remove the ash, the piston temperature will drop, and the piston pin needs to be hammered when it is installed, which will cause further deformation of piston. The correct way: put the piston into 120 ℃ oil or 100 ℃ water for heating, then take out and install the piston pin immediately.

6. When the density of electrolyte decreases due to insufficient storage, dilute sulfuric acid cannot be added.

In the use of battery, sulfuric acid in electrolyte is not consumed, but gradually transferred to the two plates with the progress of discharge, so that the density of electrolyte decreases. As long as the battery is charged by DC power supply, sulfuric acid will precipitate from the plate, and the electrolyte density will return to the original state. When the battery is not fully charged, adding dilute sulfuric acid can not increase the power, but also damage the battery. The correct way is to charge the battery after the battery is removed.

7. When disassembling and assembling the hydraulic pipe, it should not be bent arbitrarily.

The pressure loss caused by the bending of the hydraulic pipe will be far more than the normal value. The greater the pressure loss on the pipeline, the smaller the effective pressure transferred to the working parts. Moreover, after the pipeline is bent, the flow velocity and direction of the hydraulic oil at the bending place change suddenly. The resulting hydraulic shock has a great impact on the service life of the hydraulic pipeline, and even makes the pipeline explode suddenly.

8. The length of high pressure oil pipe of diesel engine can not be changed at will.

Because the time of diesel injection process is very short, the high-pressure oil pipe transmits diesel to the injector with a certain pressure and speed in the form of pressure wave. Because the high-pressure oil pipe has a certain elastic deformation, its length and diameter directly affect the diesel injection process. If the length of high-pressure fuel pipe increases, its volume also increases, which not only increases the time of pressure wave transmission, but also causes the change of fuel injection law, resulting in the delay of fuel injection time and the increase of fuel injection duration, affecting the normal progress of diesel combustion, resulting in the decrease of diesel engine power and the increase of heat loss.

9. Do not grease the ring grooves.

In order to avoid the dislocation of piston ring during installation, some operators put grease on the groove of piston ring to stick the ring, which is very harmful. When the engine is working, the butter will meet with heat to form a colloid, which will affect the elasticity of the piston ring, reduce the sealing performance, produce carbon deposition, and aggravate the wear of parts.

10. It is not allowed to install only one spring in double valve spring diesel engine.

In the high speed overhead diesel engine, there are two valve springs, one large and the other small, whose rotation direction is opposite. When one spring breaks, the other spring can still support the valve to prevent the valve from falling into the cylinder and causing accidents. The rotation direction of the two springs is opposite, and the other spring will not be stuck after one is broken, which can ensure the normal operation of the other spring. Some operators think that since there is still one spring that can work after one spring is broken, it is wrong not to replace it in time or even install only one spring after one spring is broken, which will destroy the original design requirements. Not only the spring elasticity will be weakened, but also the valve lock will fall off, which will bring serious consequences. Therefore, in diesel engines with double valve springs, when a spring breaks, a new spring with the same specification must be replaced in time, instead of just one spring.