Views: 108 Author: Site Editor Publish Time: 2019-08-27 Origin: Site
Motorcycles, driven by gasoline engines, are two or three-wheeled vehicles with front wheel steering by hand. They are portable, flexible and fast. They are widely used in patrols, passenger and freight transportation, and also as sports equipment. Today we will introduce the characteristics of motorcycle engines.
(1) The engine is a two-stroke or four-stroke gasoline engine.
(2) Air cooling is adopted, which includes natural air cooling and forced air cooling. Generally speaking, the natural air-cooled cooling mode is adopted, which relies on the running air blowing through the cylinder head and the radiator on the cylinder liner to take away heat. In order to ensure the cooling of the high-power motorcycle engine at low speed and before the start of walking, the forced air cooling method with fan and guide hood and forced air cooling radiator is adopted.
(3) The engine has a high speed, generally over 5000 rpm. The lift power (the effective power emitted by the engine displacement per liter) is large, generally about 60 kW/liter. This shows that the motorcycle engine has a high degree of reinforcement and a small size.
(4) Engine crankcase is integrated with clutch and gearbox design with compact structure.
The cylinder block is composed of cylinder head, cylinder block and crankcase. The cylinder head is made of aluminium alloy and has heat sinks. The new four-stroke motorcycle engine adopts top valve, chain drive and camshaft structure. Cylinder block materials are mostly bimetal (wear-resistant cast iron cylinder liner cast aluminium radiator) in order to obtain better heat dissipation effect.
The crankshaft of motorcycle engine is composed of left half crankshaft, right half crankshaft and crank pin. The main journal of the left and right half axles is equipped with ball bearings to support the crankshaft on the crankcase. The two ends of the crankshaft are respectively equipped with flywheel, magneto and clutch drive gear. The connecting rod is an integral structure, the big head is circular, and the needle roller bearing and the crank pin are assembled into a crank connecting rod group. When installing the piston ring in a two-stroke engine, attention should be paid to aligning the opening of the piston ring with the positioning pin in the piston ring groove so as to prevent the piston ring from rotating in the ring groove, resulting in air leakage and scratching the intake and exhaust ports on the cylinder liner.
Carburetor is an important part of motorcycle fuel supply system, located between air filter and engine intake. Generally, motorcycle engines are equipped with parallel suction inlet air flow direction, plunger throttle valve and float chamber carburetor. The structure of carburetor is mainly composed of float chamber and mixing chamber. The float chamber is located below the carburetor. There are oil pipes through the throttle switch to the tank. Through the needle valve on the float, the oil level in the float chamber is kept at a certain height, so that the oil supply pressure is stable. The function of the mixing chamber is to mix gasoline vaporization and atomization with air, so that the engine can get the required mixture under various loads and rotational speeds. It consists of a throttle valve, an injection needle, a fuel injection pipe, an air and an oil passage, etc.
Splash lubrication combined with pressure lubrication is adopted in four-stroke engine. Two-stroke engines usually adopt the mixed lubrication method of mixing a certain proportion of QB grade gasoline engine oil into gasoline. However, no matter what the engine working conditions are, the lubricating oil is supplied in a fixed proportion, which increases the consumption of lubricating oil, causes incomplete combustion, more carbon deposits and exhaust pollution. The new generation of two-stroke engines are equipped with separate lubrication tanks and oil pumps. Oil pump generally adopts reciprocating plunger variable fuel supply pump, driven by crankshaft gear through worm wheel and worm. The oil supply is changed with the engine speed through the linkage of throttle handle, steering rope and carburetor throttle valve. The oil supply is more at high speed than at low speed. The oil supply is reasonable. Compared with the mixed lubrication mode, more oil can be saved. Oil is blown into tiny oil mist by high-speed mixture, which supplies lubricating parts, reduces oil entering combustion chamber, combusts completely and reduces carbon deposit and exhaust pollution.
The starting mode of motorcycle is mainly pedal starting mode. The starting mechanism has a sector gear starting mechanism. The pedal starting transmission rod drives the fan gear, starting ratchet, clutch assembly sprocket, front chain and crankshaft sprocket to drive the crankshaft to rotate and start the engine. When the engine starts, the starting mechanism is restored to its original position by the unidirectional action of the starting ratchet and the action of the return spring. The starting mechanism can start by shifting the starting transmission rod to the neutral position and stepping on the pedal.
The other is the starting pedal type starting mechanism adopted by some imported models. Unlike the former, the clutch handle should be pinched tightly to separate the clutch when starting. The transmission rod can be placed in any grade position, without having to be in neutral gear. After starting, the clutch can be loosened and the throttle can be increased. When the starting pedal is depressed, the pawls on the starting pedal shaft mesh with the internal ratchets of the starting pedal transmission gear, which makes the transmission gear rotate. The crankshaft rotates to start the engine through idle gear, driven gear, clutch gear and starting pinion gear. After starting, the foot leaves the starting pedal rod, and the reset spring makes the pedal rod rotate reversely, and the pawl breaks away from the meshing of the internal ratchet teeth, thus restoring the original position.
If you are also a motorcycle enthusiast, then you can not miss our motorcycle tool. The first reason is for the usual small maintenance of motorcycles. The maintenance of motorcycles is relatively simple, such as changing the oil, cleaning the chains, tightening the screws, etc. It can save money and also a lot of fun. The second is when running for a long distance, you can carry them as an emergency.
