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Motorcycle engine over temperature reason and injury

Date:Oct 11, 2019

Cyclists know that motorcycle engine over-temperature will reduce the life of diesel engines, and more serious will seriously harm the safe driving of motorists. So, how is the motorcycle engine overheating caused?


The circulation system of the motorcycle engine is carried out at a high temperature, and the maximum temperature when the flammable mixture is ignited reaches about 3000 °C. The frictional heat caused by the friction of high-temperature natural gas and fitness parts will increase the temperature of components such as the piston rod, engine block and cylinder head. The high temperature is very likely to cause thermal expansion, which reduces the impact toughness of the diesel engine components, so that all normal mutual matching clearances are changed due to excessive thermal deformation. Therefore, the motorcycle engine must have a reliable refrigeration system to ensure that the diesel engine is working properly. The normal operating temperature of the motorcycle engine can not be too low or too high, usually the grease temperature is 56 ° C up and down is appropriate. When the temperature of the air-cooled engine oil is above and below 98 °C, and the temperature of the air-cooled diesel engine is around 96 °C, the output of the diesel engine will be too high, which will reduce the output power and increase the noise. As a result, the diesel engine is not turned off when the ignition switch is turned off. A diesel engine cylinder head and oil on the engine block will be burnt, and the diesel engine will have a grease leakage problem, indicating that the diesel engine is working abnormally and there is an over-temperature common fault.


The adverse effect of over-temperature of diesel engine is relatively large, because over-temperature will lead to lower engine power, accelerate fatigue, and increase fuel consumption; because of over-temperature, the diesel engine is abnormally ignited; because of over-temperature, the grease mold zooming factory, fitness parts The film in the middle is destroyed, and the damage of the parts is aggravated; because the over-temperature causes the drive shaft to smash the head rolling bearing, the piston ring is broken, the cylinder is pulled, and the cylinder is held, which reduces the service life of the diesel engine and seriously jeopardizes the safe driving of the driver. More causes the motorcycle engine to overheat


First, the new car and overhaul car do not pay special attention to the running-in period

Newly purchased motorcycles and overhauled vehicles, because the surface of the parts is not smooth, the geometrical appearance of the parts and the assembly line have the necessary errors. The main parts of the friction parts are smaller, and the total area touched by the enterprise. The working pressure is very high, the wear rate is increased rapidly, and the heat generated by the friction is relatively large. Therefore, the new car and the overhaul car should pay special attention to maintenance and maintenance and give a running-in period. In the running-in, it is necessary to limit the speed and load, and immediately maintain and replace the grease. In fact, many new car buyers, especially those who are in the three-wheeled passenger cargo motorcycles, do not care about the maintenance period and maintain the car according to the instructions in the manual. Some of them drive over the mountains during the running-in period of the new car, speed limit, request timeout, overload operation, and the grease is not removed after thousands of kilometers of running-in, resulting in over-temperature of the diesel engine.


Second, the maintenance assembly process is not good

Some motorcycle maintenance workers use the iron hammer to strike when overhauling the engine. After the two-stroke engine is disassembled several times, the transmission shaft rolling bearing hole is enlarged, causing the rolling bearing to cooperate with each other with poor precision. The rolling bearing runs through the inner hole. Correctly select the tinplate in the inner hole of the rolling bearing and repair it in the way of punching, which causes the rolling bearing to be different after the crankcase is closed. There are also some new drive shafts that need to be replaced during maintenance. The quality of the spare parts is weak, and the motor shafts have different shaft degrees of more than 0.05 mm. When the upper and lower crankcases are close together, the rotation of the transmission shaft is inconvenient when the engine block, the piston rod and the piston ring are not installed, and the frictional friction resistance is relatively large, resulting in overheating of the diesel engine.


Because the diesel engine crankshaft connecting rod big head rolling bearing is seriously damaged, the upper and lower drive shaft rolling bearing is not installed in time. After the driving shaft is installed, the vertical axis of the crankshaft connecting rod has no engine cylinder management center, which causes the crankshaft to tilt up and down and the piston rod is in the The yaw in the engine block makes the piston ring and the engine block eccentric, and the cylinder pressure is lowered, causing the diesel engine to overheat. Four-stroke engine engine cam

The damage of the shaft camshaft is serious, the aspect ratio of the camshaft is insufficient, and the lift of the exhaust shaft of the camshaft rocker arm is small, so that the exhaust pipe is blocked and the displacement is insufficient, resulting in overheating of the diesel engine.


Third, poor lubrication

The grease of the four-stroke engine is also responsible for the heat dissipation of the heat pipe during the entire operation of the diesel engine. According to the high-pressure oil pump circulation system, the heat generated by its own digestion and absorption, and the heat generated by the digestion and absorption of its spare parts, will release the heat according to the whole process of the moisturizing circulation system, so that the components of the diesel engine are evenly heated. When the high-pressure oil pump is destroyed, the amount of oil pump is insufficient, the quality of the grease is poor, the grease is mildewed or the grease is lacking, the heat-dissipating heat pipe heat-dissipation becomes weak, causing the moisturization condition to be malignant, the friction intermediate oil film is cracked, the damage is aggravated, and the diesel oil is caused. The engine is overheated.


Fourth, the heat pipe standard deviation

The air-cooled two-wheeled motorcycle, because of the unscientific installation, makes the diesel engine reverse water cooling cyclone encounter resistance, and the water cooling exhaust air volume is too small, resulting in overheating of the diesel engine.

The mandatory air-cooling type is a good result of water cooling in a small-displacement motorcycle diesel engine refrigeration system. Because the water-cooled fan blade in the forced air-cooled device is destroyed, the fan is split and lost, and the air hood is burned and glued to the cylinder head or the engine block radiator by the engine block and the cylinder head, resulting in water cooling wind. The total flow is not enough, the working pressure is small, the air hood can not effectively distribute the total flow of the wind, and the fine sand of the diesel engine casing due to the smashing of the stern adheres to the heat pipe, which causes the diesel engine to overheat.


A water jacket is arranged under the cylinder of the cold diesel engine, and the water cylinder of the cylinder head communicates with the water passage of the engine cylinder. The water jacket is filled with cooling circulating water, and after the engine is warmed up, the cooling circulating water is also warmed. During operation, in order to maintain the temperature balance, the high-temperature cooling circulating water is pumped by the centrifugal water pump to the heat pipe radiator to dissipate a part of the heat, and then return to the cylinder water jacket. In order to avoid steam due to excessive temperature, most of the air cooling system software is equipped with a temperature regulating valve (thermostat). The inlet valve of the thermostat is turned off before the operating temperature of the diesel engine is exceeded. The circulation system of the water is limited to the small circulation system between the engine block and the thermostat. When the temperature rises to 63 ° C -90 ° C, the pressure regulating valve is slowly opened, and the cooling circulating water is pumped into the heat pipe radiator to generate a large circulation system, thereby dissipating a large amount of heat. When the temperature rises to the zero point, the thermal switch will be fully automatic, and the fan will rotate, which will improve the actual heat dissipation of the heat pipe. When the air-cooled diesel engine thermostat is destroyed and the temperature rises to 83 °C, the pressure regulating valve is still not easily opened (or not all open), and the cooling circulating water is only used as a small circulation system, causing the diesel engine to overheat. When the chilled liquid added to the air-cooled diesel engine is hard water that has not been solved, because there are many minerals in the hard water, it is very easy to produce dirt at high temperature, the volume of the water jacket is reduced, and the components such as the water pipe heat pipe radiator are blocked. The actual effect of heat pipe cooling causes the diesel engine to overheat. On the other hand, due to the damage of the heat pipe radiator, the deformation of the heat pipe radiator and the waste of the outside, the leakage of the inlet pipe, the discharge of the refrigerant when the refrigerant is filled, or the destruction of the fan motor and the thermal switch, the temperature rises and the diesel is caused. The engine is overheated.

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