Currently, China's motorcycles are mainly concentrated in 50mL, 70mL, 80mL, 90mL, 100mL, 110mL, 125mL, 150mL and other small and medium-displacement models, while there are very few medium- and high-displacement models of 250mL, 350mL, 400mL, 750mL and above, and some of them are even vacant. This shows that the technical level of China's motorcycle production is limited to medium and small displacement low-speed vehicles, and is too centralized. For example, there are 256 models of certain types of trans-type engines (e.g., CG125 tappet models) with similar appearance. Simple repetition, one side of a thousand vehicles, and general level are the characteristics of China's motorcycle varieties, and there are only a handful of products that are truly personalized and have independent intellectual property rights as the marking of the enterprise, and there is still no real mastery of the development capability and mature technology of medium- and large-displacement and high-speed vehicles.
In order to effectively protect the living environment of human beings and to implement the "Law of the People's Republic of China on the Prevention and Control of Air Pollution" to strictly control pollution from motor vehicles, the State Environmental Protection Administration (SEPA) has issued a public announcement that since January 1, 2005, mopeds and motorcycles within the country's territory have begun to implement the testing of the equivalent of the Euro II emission standards, and that from July 1, 2005, the production and sale of mopeds and motorcycles which do not meet the Euro II emission standards will not be permitted. Mopeds and motorcycles are not allowed to be produced and sold that do not meet the Euro II emission standards. However, a very small number of enterprises to digest the inventory of motorcycles as the reason, but also disregard for the national law, still producing motorcycles do not meet the Euro II emission standards, in the engine crankcase body on the 2004 machine number, in order to cope with the inspection of the relevant departments, if this phenomenon is not completely changed, really worrying.
It is worth noting that some manufacturers, in order to pursue profits, have made variant designs for the local appearance of the vehicle and engine type, such as air-cooled to water-cooled, expanding the cylinder and so on. Particularly serious is the expansion of a 125mL engine (air-cooled models, water-cooled models) into a 150mL displacement engine, mounted on the original design of 150mL displacement motorcycle, belonging to the typical small horse-drawn car. These small-displacement engines only after a simple cylinder expansion (i.e., increase the piston, piston rings, piston pins and cylinders), other components such as the crankshaft connecting components, crankcase and main bearings and other support parts, moving parts basically did not change, the engine has no reserve power and torque, so that the engine is always in a high-speed, high-temperature, high-load state of running in advance of the engine's kinetic energy, so that the parts of serious wear and tear, and ultimately lead to The engine's service life is greatly shortened.
Improving the quality of motorcycles and engines, parts and components is the key. At present, the quality level of motorcycle parts and components in China is generally not high, and there are not many influential and large-scale production enterprises. Most of the enterprises are unable to realize the technological transformation and introduction of equipment due to the limitation of capital, thus falling into a vicious circle of technological backwardness, declining quality, and decreasing profit. Especially in recent years, the motorcycle industry has gone through several battles, those small enterprises that have not formed product scale and lack of competitiveness disregard product quality, rely on counterfeiting, assembling, tax evasion and other illegal means to reduce the price, which greatly disrupts the normal order of the motorcycle market and makes the product quality declining year by year, which casts a shadow over the motorcycle industry in China, although after short-term remediation, it has yielded little result. The motorcycle industry has been suffering from a lack of quality, and is in urgent need of remediation and improvement.
Through the market survey and relevant information in recent years, China's motorcycle engine mainly exists in the following aspects of the problem.
One, the parts of the material problems or improper heat treatment
1. Piston ring elasticity decreased, piston ring and cylinder clearance increased (especially after the new car break-in period of 1,500-5,000km), resulting in a decline in engine power, shortened service life.
2. Output shaft fracture, transmission gear broken teeth, oil pump gear broken teeth (powder metallurgy quality is not up to standard), valve rocker arm fracture or abnormal wear and camshaft combined with the R arc surface.
3. Timing chain elongation accelerated or broken, connecting rod small head bearing cage broken.
4. Cylinder gasket damage, part of the stainless steel gasket on both sides of the fluorine rubber coating, poor adhesion, use time is not long to fall off, so that the cylinder head and the cylinder block combined surface leakage, resulting in starting difficulties, power loss.
Second, the poor quality of the parts themselves (low manufacturing level)
1. Due to the poor manufacturing quality of oil seals, short durability, resulting in oil seepage and leakage of oil at the spindle and output bearings.
2. Cylinder head, cylinder block and other aluminum alloy castings manufacturing process level is low, the casting quality is not guaranteed, resulting in pinholes, sand holes and other casting defects, resulting in this part of the parts of the poor density. When the engine is working, the heat in the combustion chamber is not emitted, so that the parts are overheated, the power drop.
3. Valve stem working parts of insufficient hardness (some even without heat treatment), easy to wear, shortened service life.
4. Poor straightness of the valve guide hole, so that the valve movement is blocked, causing overheating, and in severe cases will cause the valve to stall in the guide hole.
5. The valve guide outer circle and inner hole concentricity is too poor (i.e., valve guide oil seal), the oil seal use time soon, the main lip of the abnormal wear and tear, which led to the phenomenon of exhaust blue smoke, and the replacement of a separate valve guide oil seal is ineffective.
6. Live race material or line type is not right, the engine work, the piston skirt by thermal expansion abnormal deformation, so that the friction sub-parts of the wear increased.
7. Camshaft bushings concentricity is poor, so that the camshaft produces eccentric movement, resulting in serious wear and tear of its journals, triggering the cylinder head rattling.
8. The tooth shape of the gear wheel is seriously out of tolerance, causing abnormal meshing.
Three, the hidden dangers of the fuel supply system
1. Due to the low level of craftsmanship, simple equipment, poor manufacturing precision, carburetor fuel supply system of the main amount of holes, idling amount of holes and air amount of holes in the internal surface machining dimensions and roughness does not meet the design requirements, the comprehensive flow rate of the scattering of the difference between the large, resulting in the air-fuel ratio is not appropriate, the engine fuel consumption, and the impact of the combustion of the engine and emissions.
2. Due to the processing quality and selection of rubber seals quality is not qualified, as well as float arm, float frame rigidity or float needle valve rubber layer is not gasoline-resistant and aging deformation, the use of a short period of time there will be a high oil level and the float chamber leakage combined surface.
Four, the hidden dangers of the ignition system
1. Magneto failure is mainly high-voltage coil insulation strength is not enough, poor voltage resistance, in continuous operation is prone to breakdown (this failure is higher in summer). The main reason is that the high-voltage coil of the enameled wire quality is poor, easy to peel paint, some small factories can not guarantee the paint dipping process.
2. Capacitor discharge ignition device components of the screening is not strict, electrical components are easy to aging, so that ignition interruption.
3. Due to the processing and manufacturing quality problems, there is even the phenomenon that the magnet is thrown out.
4. Spark plug skirt end cracking, the main and side electrode fusion or spark plug electrolysis is easy to breakdown, short service life.
V. Hidden dangers in the cooling system
Some models have poor cooling effect due to innate design problems. In the engine at full load, resulting in overheating, so that the moving parts stuck, parts damage, sealing performance damage, etc.. The main reasons for this are as follows.
1. Improper clearance design or assembly of moving parts.
2. Cylinder head and cylinder block waterway casting narrow, so that the cooling water flow is blocked, the heat is not distributed.
3. Poor quality of the water pump, the flow rate is small, so that the cooling effect is reduced.
4. Radiator selection of poor material or its internal channel is narrow, easy to block, slow heat dissipation.
5. Poor reliability of thermostat, temperature control switch, fan motor and other sensor parts.
6. Poor quality of rubber for water pipes (some use recycled rubber), easy to aging and cracking, resulting in cooling system leaks, etc., triggering overheating failure.
Six, the hidden dangers of the lubrication system
1. Oil pump quality is not good, the pump and the inner and outer rotor clearance is too large, so that the oil flow is reduced.
2. The engine crankcase oil channel design is unreasonable, the oil channel is narrow, the oil delivery is blocked.
3. Improper selection of lubricants, such as 253FMM engine (configured with a twin-cylinder 250mL motorcycle) thermal load would have been high, should be selected 20W/50 special high-temperature lubricants, while a few manufacturers choose 10W/30 lubricants, so that the engine does not have effective lubrication, resulting in overheating of the parts, wear and tear increased.
The consequences of the above problems will make the lubrication effect is reduced, the movement of friction parts abnormal wear and tear, and even lead to serious failures such as cylinder pulling.
Seven, the hidden dangers of assembly quality
1. cylinder head, cylinder block tightening torque is not enough to make the combination of plane distortion, caused by the loosening, resulting in compressed gas leakage, overheating parts of the engine power decline and other failures.
2. Assembly cleanliness is poor, the engine does not work for a long time, the oil pump filter will be blocked by foreign objects.
3. engine assembly process, too much glue (such as the crankcase on the plane of the oil channel and the cylinder head bolt root combination), so that the lubricant oil circuit is blocked, resulting in the cylinder head camshaft and bushings and other parts of the oil lubrication, causing abnormal wear.
4. magneto flywheel lock nut or screw loose, so that the rotor and the crankshaft on the semicircular key to produce shear displacement, affecting the engine ignition timing.
5. The magneto wiring is open and welded, interrupting ignition.
6. The carburetor needle is installed incorrectly or the clamp falls off, causing the engine to fail to work properly.
7. When the engine is shipped from the factory, the fuel in the float chamber is not drained according to the regulations (especially for scooters, which are inconvenient to drain due to structural limitations). Storage time of more than a month, the carburetor volume hole due to gasoline oxidation and deterioration of the phenomenon of blockage, the engine can not start.
Eight, the hidden danger of engine accessories
1. Engine accessories in the air filter cartridge, such as foam (commonly known as sponge) of poor quality, intolerant of gasoline and oil, use time will not be long aging and cracking; air filter parts of the bonding quality is poor, by the vibration of the bonding at the cracking off, so that the dust into the carburetor, the cylinder, resulting in the amount of holes clogged and cylinder wear and so on. A series of failures.
2. The exhaust muffler is made of poor muffling materials, and the internal structure is unreasonable or the internal welding is of poor quality. Soon after the muffler is used, the spacer plate and other parts will be desoldered and loosened, and the noise of the motorcycle will increase.
3. Some engine factories, when choosing carburetors, air filters, exhaust mufflers and other accessories, did not conduct selection tests and vehicle matching tests, and the accessories used were improperly matched to the engine, so that the engine's power and torque could not be properly utilized, and its main performance indexes could not reach the original machine's design level. Eventually, the motorcycle will have difficulty starting, overheating, poor acceleration, no speed, and a much shorter service life.
Nine, shoddy parts of the hidden dangers
China's vast majority of enterprises have set up quality management organizations, a set of rigorous testing equipment and the necessary testing gauges, under normal circumstances, does not meet the technical requirements of the product drawings of the parts, are found in the quality of the spot check when the exclusion. However, it is these parts that are rejected by the quality sampling inspection of the production enterprises and have serious quality problems, due to the lack of systematic and formal quality management in the motorcycle parts market, they flow into the parts market in a dignified manner. When these shoddy parts are mounted on the engine, they can cause a series of failures, such as motorcycle hard starting, unstable idling, engine overheating, poor acceleration, and loss of power.
There is an old Chinese saying: "If you don't have far-reaching worries, you will have near worries". At present, China's motorcycle engine production quality problems, if not improved as soon as possible, will bring serious consequences to China's motorcycle industry, should cause the motorcycle industry people attach great importance to. In order to improve the quality and reliability of motorcycle engine products. The first is the elimination of backward products
China's current production of most of the motorcycle engine models, the Department of foreign products developed in the 1950s and 1960s (a very small number of models developed in the 1970s and 1980s). Such as 1E39QME, 157FMI, 1P2QMI, etc., the performance indicators of these models with the same displacement of other models lag behind a lot. Even if the quality is good, they cannot adapt to the requirements of low fuel consumption and high environmental protection. Some engines are structurally inherent problems (such as long-stroke, low-speed type), so that it can not reach a more advanced level. Especially than the quality difference is too large, must be updated as soon as possible.
The second is to improve the existing products and the development of new products
1. Improvement of existing products must be strengthened engine, increase the average effective pressure and thermal efficiency; improve the shape of the combustion chamber, the use of high compression ratio of the compact combustion chamber; improve the cooling system, the use of forced air-cooled and liquid-cooled.
2. Adopt multi-valve and overhead camshaft type. China's current production of motorcycle four-stroke engine, the vast majority of 2-valve structure, only the latest development of the CL2V60MM engine and VF125 engine for the 4-valve structure. Multi-valve structure not only adapts to the requirements of high power, but also realizes low fuel consumption. The use of overhead camshaft can reduce the number of moving parts of the gas distribution mechanism and shorten the transmission distance, improve the reliability of the gas distribution mechanism, and help reduce the inertia of the mass of the gas distribution mechanism and increase the speed of the engine. As for the tappet drive air distribution mechanism will be eliminated sooner or later.
3. Adopt variable technology. Variable technology is based on the engine speed of its intake and exhaust system for automatic adjustment, in order to achieve a wide range of speed with a large torque output and more ideal power performance, is to improve the economy of the engine is a new technology, but also a direction of the future development of four-stroke engine.
4. Development of electronically controlled gasoline injection technology. The use of electronically controlled gasoline injection technology is to achieve efficient combustion of gasoline engines and clean emissions of one of the most simple measures. At present, some domestic enterprises have developed EFI motorcycle engines, whose emissions fully comply with Euro II emission standards. Practice has proved that EFI engine is a green product that reduces fuel consumption and emissions and purifies the environment, and has been widely used in foreign countries.
5. Improve product reliability. According to relevant information, Europe, the United States, Japan and other motorcycle powerhouse of a variety of gasoline engines, has long been the implementation of more than 200h of full-load intensive testing, the average fault-free interval of more than 1,000h. In the 1980s in our country will be the reliability of engineering applications to the internal combustion engine industry, and only 100h of intensive testing (which includes 20h of low-load break-in operation), the actual full-load test only 80h. 80h. As soon as possible to take practical and effective measures to improve and implement to the motorcycle product testing, to the advanced level of foreign interference.
6. The pursuit of quality and price. For quite a long time, China's motorcycle industry sales policy, has been inexpensive. Thus, the formation of a nationwide reduction in the cost of motorcycle engine prices (also including motorcycle vehicles), resulting in product quality along with the price of the phenomenon of declining, but also the name: cheap and beautiful! Now that we have entered the 21st century, we must reflect on the "cheap and beautiful" to the people brought about by the misleading, because cheap and beautiful is contrary to the objective law. People know, a penny a penny reason. The price is lowered, the quality can go up? We start now, we must strictly good engine parts quality, strengthen the engine processing parts and assembly control, resolutely eliminate unqualified products, the pursuit of quality and price, in order to improve the quality of China's motorcycle engine products, lay a solid foundation.
In summary, at present, the quality and reliability of China's engine products have lagged far behind the foreign advanced level. Motorcycle companies want to survive and develop in the fierce competition in the domestic and foreign markets, a place, we must pay attention to product quality, improve product reliability on the hard work. In this sense, to build China into a world motorcycle powerhouse, there is still a long way to go. As soon as possible in a relatively short period of time to narrow and catch up with foreign advanced level, is still China's motorcycle industry's goal. To this end, we raise our arms and call: work hard, China motorcycle!