Motorcycle school Ⅰ- What you need to know about motorcycles


Nowadays, motorcycles are given different meanings. Motorbikes have become a way of life for millions of people. They don't want to be surrounded by aluminum alloy cars. The light weight and high power of motorcycles allow riders to feel the feedback from the road and pursue the passion of speed!

This article will let you know more about your motorcycle, and I will briefly introduce each part of the motorcycle.


1. Engine

Engine is the power source of motorcycle, which directly affects the mobility, economy, reliability and durability of motorcycle. Today's motorcycle is commonly used is the gasoline engine, the engine is generally through the carburetor, so that gasoline and air mixed into the cylinder, after the compression of the mixer by spark plug generated spark ignited, and the fuel combustion generated heat into the power of driving the motorcycle (mechanical energy). This energy conversion takes place in the engine cylinder. By the intake, compression, combustion expansion (work), exhaust four processes of the working cycle to achieve.

2. How an engine works

At present, the most common type of reciprocating piston gasoline engine is gasoline, which has two strokes and four strokes.
The crankshaft turns once, the piston in the cylinder reciprocating movement once, through two strokes, complete the intake, compression, combustion expansion, exhaust a working cycle of the engine, known as a two-stroke engine.
The crankshaft turns once, the piston moves twice in the cylinder reciprocating, experiencing four strokes, completing the intake, compression, combustion expansion, exhaust a working cycle of the engine, known as a four-stroke engine.

1) How a four stroke engine works

Intake stroke

The piston moves from top TDC to bottom TDC in the cylinder, opening the intake valve and closing the exhaust valve.

Compression stroke

The piston moves from BDC to TDC in the cylinder, and the inlet and exhaust valves are closed.

Combustion expansion stroke

The piston moves from TDC to TDC in the cylinder, and the inlet and exhaust valves are closed. The burning mixture expands rapidly and pushes the piston down, and the connecting rod drives the crankshaft to rotate and output power.

Exhaust stroke

The piston moves from BDC to TDC in the cylinder, when the intake valve closes and the exhaust valve opens.


2) How a two stroke engine works

The piston moves from BDC to TDC, mainly completing the air intake and compression process.

The piston moves from top TDC to bottom TDC, mainly completing the combustion expansion and exhaust process.


3. Engine construction

The overall structure of the engine is composed of base fasteners, pistons, crankshaft connecting rods, valve mechanisms, intake and exhaust systems, cooling systems, lubrication systems, ignition systems and pneumatic devices.

Base fastener

Mainly includes cylinder head, cylinder block and crankcase.

Basic fastener function

Support and install other parts of the engine, withstand the engine when the work of all kinds of impact force and torque, the foundation fixed parts make the engine skeleton, determines the overall stiffness and strength of the engine.

The piston group

The purpose of the piston group is to combine the cylinder head with the cylinder block to form the combustion chamber and transfer power to the crankshaft connecting rod group.

Crankshaft connecting rod group

The linear reciprocating motion of the piston is transformed into the rotational motion of the crankshaft, so as to output power and drive the work of relevant accessories. Crankshaft connecting rod group mainly includes connecting rod and crankshaft and other engine main moving parts.

Distribution agency

Function: according to the requirements of the engine, the combustible mixture is regularly sucked into the cylinder, and the exhaust gas is regularly discharged from the cylinder, so as to ensure the normal operation of the engine.

Lubrication system

Lubricate the contact surface of moving parts in the engine to reduce friction and wear, and take away heat generated by friction, so as to ensure the normal operation of the engine, improve its reliability and prolong its service life.

1) The lubrication mode of two-stroke engine has two kinds of mixed lubrication type and separated lubrication type.

2) Four-stroke engines generally adopt a comprehensive lubrication mode combining splash lubrication and pressure lubrication, and their lubrication system mainly includes oil pan, oil pump, oil filter, oil passage, oil pipe, etc.

The cooling system

Cool the engine to ensure proper engine operation.

Most motorcycle engines are cooled by natural wind, that is, the air flow when the motorcycle is running, and the heat of the engine is taken away by the radiator of the cylinder block and the cylinder head.

At present, the engine also adopts forced air cooling, water cooling and oil cooling.


The frame is the skeleton of a motorcycle that supports the engine, transmission, seat cushion, fuel tank and motorcycle occupant, and provides mounting position for the vehicle so that the entire vehicle supports the wheels. The frame is the main support part of the motorcycle, but also to receive impact and vibration in the driving, so the material and structure must have considerable strength and stiffness, but also requires light quality, so as to tell the driving.

Material: low carbon steel, aluminum alloy, magnesium alloy.


1) Spatial structure frame

With high strength, it is mainly used for large motorcycles and cross-country motorcycles and racing cars with strict operating conditions

-- Straddle diamond frame

Beam under the frame of the pipe from the head down to the engine crankcase front-end, saves the engine at the bottom of the frame part, using the engine itself as part of the frame, connect discontinuous frame, the frame number for medium displacement motorcycle, especially on off-road vehicles, in order to obtain the ideal minimum height from the ground, This kind of frame form is used more

-- Cradle frame

In this frame structure, the engine is installed on the frame as if a baby is placed in a cradle, so it is called cradle frame.

This frame is ideal in terms of strength and stiffness, so high-power motorcycles, racing motorcycles, cross-country motorcycles are widely used in this frame.

According to the structure of the bracket under the engine, it is divided into double row tube cradle frame, fork tube cradle frame, single tube cradle frame.


2) Main beam structure frame

The main beam structure frame is simple in structure, simple in process, light in weight, but weak in carrying capacity. It is more suitable for motorcycles and mopeds with small engine power.

-- the u-shaped frame

Low strength, weak bearing capacity, mostly used for light motorcycles.

-- Plate frame

The frame is welded from two sets of symmetrical stamped steel plates and has no lower beam tube. The frame can also be used as part of the appearance or other functional parts (such as fenders).

This kind of frame maintenance is not convenient, and because of the stability of the plate is limited, generally used for the engine power of the motorcycle.

-- Combined rocker arm frame

The motorcycle engine is not completely fixed on the frame, but the engine, rear wheel fork, drive device, rear axle and so on constitute a whole, in the engine body is arranged on the contact, and the frame is hinged to form a combination of rocker arm structure.

There is no independent rear fork in the frame, and the engine swings relative to the body in motion, i.e. up and down around the hinge point on the body with the rear shock absorber.



The bearing system

Bearing system mainly refers to the motorcycle used to bear the body weight and the weight of members and cargo functional structure. Including flat fork, footrest, main station frame, side bracket, rear shelf, etc., the material is mainly steel and aluminum alloy parts, but also the use of magnesium alloy, individual rear shelf has plastic parts.

—— flat fork

The rear wheel flat fork connects the rear wheel to the frame, and through the rear shock absorber the rear wheel can be around a fixed point on the frame for a certain range of up and down to cushion the impact of the rear wheel

Rear wheel flat fork construction

In order to ensure that the rear wheel flat fork can swing around the fixed center of the car body, the rear wheel flat fork and the car body are equipped with sleeve or bearing, which makes the rear wheel flat fork flexible and reliable when shaking

1) Axle sleeve rear wheel flat fork

In the rear wheel flat fork head and motorcycle body connected in the two mounting holes, are provided with axle sleeve, so that the rear wheel flat fork can be flexible up and down, and in the left and right direction of the pendulum momentum is very small.

2) Flat fork of rear wheel of bearing

In order to make the rear wheel flat fork more reliable work, some large motorcycles in the rear wheel flat fork head and motorcycle body connection using bearings to replace the sleeve, and other parts with the sleeve of the rear wheel flat fork.



The intake system of motorcycle engine is composed of air filter and intake pipe. Its role is to guide and filter the air, reduce the intake noise, and control the mixed gas volume entering the engine

The structure and working principle of the intake system

The role of the air filter to filter, purify the air into the cylinder, prevent dust in the air, sand and other particles into the cylinder, to reduce the cylinder, piston and piston ring wear, its working performance of the engine power, intake noise, and service life is very affected.

Inlet pipe

The carburetor atomized mixture enters the engine cylinder from the engine inlet through the intake pipe, which reduces the heat transfer from the engine to the carburetor and isolates the impact of engine vibration on the carburetor.


The role of the exhaust system makes the engine work exhaust gas discharged into the atmosphere, and reduce the exhaust noise and exhaust gas temperature, eliminate the flame spark in the exhaust gas, well designed exhaust system can improve the intake and exhaust efficiency, increase the engine power, reduce fuel consumption

Exhaust system includes exhaust pipe and muffler, now usually the exhaust pipe and muffler welding as a whole, collectively known as exhaust muffler.

The structure and working principle of exhaust pipe

The exhaust pipe in the exhaust muffler is made of bent steel pipe, which is located between the engine exhaust port and the muffler, and its role is to guide the exhaust gas from the engine to the muffler.

Muffler is the main part of exhaust muffler, used to prevent sound transmission and allow airflow through a device, when the elimination of air power noise is an important measure.


According to the different rotating elements of the brake, it can be divided into drum brake and disc brake.

According to the transmission mode of braking system control force can be divided into: mechanical brake, hydraulic brake and pneumatic brake.

According to the operation mode, it can be divided into: front and rear wheels linkage braking, and rear wheels two sets of independent braking.

1. Disc brake

Divided into mechanical and hydraulic two types, at present in the motorcycle most of the use of hydraulic disc brakes.

Disc brake is generally composed of brake lever, brake main cylinder, storage cylinder, brake calipers, brake disc, brake tubing and so on.

When braking, the brake lever compresses the master cylinder, making the pressure rise in the hydraulic system, pushing the piston in the brake caliper, pressing the friction plate on the brake disc, so that the brake disc fixed on the wheel gets the braking torque.

The features of disc brake make the work soft, self-cleaning, not easy to malfunction.

2. Drum brake

It consists of brake drum, brake shoe block, brake CAM, brake arm, support shaft, reset spring, brake drum cover and so on.

Drum brake is usually the internal drum brake, the brake shoe at one end of the impulse, can swing around the other end of the fulcrum, pressure on the inner surface of the brake drum, friction torque.


Motorcycle electrical system is composed of control part, power supply part, electricity part and ignition part connected by wire.


Generally by the generator and battery two main components.

Main function: in the closed circuit of the motorcycle itself, the generator and the battery work in parallel to provide the electric current to the electric part of the electrical system, and store the excess energy in the battery.

The generator can be divided into DC generator and AC generator according to the nature of its output current.

Alternators can be divided into flywheel alternators, magnet rotor alternators and three-phase alternators according to different structures.


Structure and principle of dc generator (magneto)

The dc generator works according to the principle of electromagnetic induction, that is, when the wire moves perpendicular to the magnetic field line in a uniform magnetic field, the induced electromotive force will be generated in the wire. If the wire and other external circuits form a closed loop, the induced current will be generated in the wire, and the direction of the current will be judged by the right hand rule.

Structure and principle of alternator (magneto)

The mechanical energy of the prime mover is converted into electrical energy output by using the principle of electromagnetic induction, in which the electric potential is induced by cutting the magnetic force line with the wire.



Motorcycle battery has the following characteristics: light weight, small volume, good sealing performance and shockproof performance. Lead acid battery also has the advantages of small internal resistance, voltage stability.

The basic structure and working principle of animal battery

It mainly consists of a shell, a shell cover, a plate, an electrolyte and a separator

The housing is made of hard rubber or plastic resistant to acid, heat and vibration, and is divided into three or six separate parts according to the rated voltage of the battery. Electrode plate is the main working substance for charging and discharging chemical reaction of battery. It is made of lead-antimony alloy sheet coated with active substance after electrochemical treatment. The plate is divided into positive plate and negative plate.


Lighting signal unit

Including headlights, position lights, taillights (license plate lights), instrument lights, etc., the main role of the motorcycle in the night when driving to provide lighting for the driver and remind other vehicles to pay attention to safety, to ensure the safety of driving.

Signal device also includes steering indicator light, horn, gear indicator light, brake light, etc., used to remind the driver and relevant personnel of the vehicle running state, and the driver's operation intention through sound and light signal expression.


In the electric system of motorcycle, the control part is used to ensure the normal work of the power supply part and the electric part respectively, as well as the harmony between them, and make the driver control the electrical system at any time.

The control part mainly includes regulator, rectifier, flash relay, starting relay, fuse and control switch and cable assembly.


Front shock absorber is the elastic link part between front wheel and car body. It supports the quality of the car body, absorbs the impact of the road on the vehicle and the occupant, and rapidly attenuates the vibration, buffers the force of the vehicle components, prolongs the service life, and improves the comfort of riding and the stability of handling.

Construction of front shock absorber

To bearing and absorb the impact of the front wheel received, before have a damping spring shock absorber, if the damping spring is soft, riding will be more comfortable, while the impact of a large, asked for a damping spring force is bigger, so the variable stiffness spring is adopted in some models to meet the needs of the two aspects, in order to better vibration absorption and attenuation, set up in most front shock absorber damping device.

Construction of rear shock absorber

After the shock absorber is mainly by the axial force, in order to absorb the impact of the rear wheel by, after the shock absorber damping spring and damper, arrangement of damper in the shock absorber is divided into the upper and under, and there are multiple forms of damper, according to the different forms of damper, after the shock absorber can be divided into hydraulic damping shock absorber, after filling air after the shock absorber damping type and shock absorbers.

Steering column

Steering column is consist of subject, triple clamp and thrust bearing.


The fuel system consists of fuel tank, fuel switch, fuel oil gauge, fuel filter, oil pipe and so on. Fuel switch is equipped with fuel filter device, but in order to ensure the fuel quality into the carburetor, a fuel filter is set between the fuel switch and the carburetor.

1. Fuel tank

1) The fuel tank is usually made of 0.8-1.0mm thick steel plate stamping and welding, and some of the internal fuel tank is welded with a hole partition, which not only improves the strength of the fuel tank, but also can prevent the fuel shock when the motorcycle is running.

2) The top of the fuel tank is provided with a refueling port, and the cover of the oil tank with a vent hole, so as to prevent fuel overflow in the vehicle running, but also to ensure the balance of air pressure inside and outside the tank, so that the fuel can flow out naturally.

3) Most of the motorcycle's fuel tank is arranged above the frame beam tube, located between the handlebar and the seat cushion, which requires the appearance of the fuel tank should be beautiful, and consistent with the vehicle's styling style.

2.  Fuel switch

Fuel switch can be divided into manual switch and automatic switch two categories, and manual switch is divided into plane guide type and spool guide type two.

1) Flat through-type fuel switch

When the handle is placed ON location of fuel oil in the tank body by main tubing into the switch of main oil way, the handle of the oil duct into the lower part of the switch body oil duct, and then into the precipitation cup, after screen flow from the nozzle, when the handle is placed in the RES position, fuel is entered into the switch body spare oil filter tubes of spare oil, lower tubing into the precipitation cup by the handle and switch body, When the handle is placed in the OFF position, the switch body and the oil channel in the handle are staggered, the oil channel is cut OFF, and the oil supply stops.

2) Spool conduction type fuel switch

When the handle is turned to make the oil hole on the conical valve core and the oil channel hole on the switch body relatively positive, the oil channel is on, otherwise it is closed

3) Automatic through-type fuel switch

When the engine is running, the pressure fluctuation in the intake tube suction fuel switch through the pressure tube, due to the role of negative pressure film and pressure hole, in the negative pressure chamber to form a relatively stable negative pressure, so that the diaphragm moves down, the oil circuit conduction; When the engine stops, the negative pressure chamber pressure is the same as the atmosphere, the diaphragm is reset under the action of the reset spring, and the oil circuit is cut off.

3. Fuel oil gauge

It can be divided into mechanical oil gauge and electronic oil gauge.

4. Fuel pump

Common fuel pump vacuum diaphragm type fuel pump, the pressure tube will be the engine inlet tube pressure fluctuations into the fuel pump, when the engine inlet tube is negative pressure, the diaphragm moves up, so that the suction valve is opened, the output valve is closed, fuel from the suction chamber into the middle chamber. When the engine intake tube is positive pressure, the diaphragm pressure down, so that the output valve is open, the suction valve is closed, fuel from the middle chamber into the input chamber; If the needle valve of the carburetor float chamber is closed at this time, the pressure of the output chamber increases, the drain valve opens, and the fuel oil of the output chamber flows back to the suction chamber through the drain valve.



1) The handlebar is connected with the upper triple clamp, centered on the riser, and the front shock absorber is rotated through the direction column to control the steering of the front wheel.

2) Other operating functions: the direction of the right end is the throttle handle, control carburetor throttle; The right handle is the front brake handle, the left end of the direction handle is usually a fixed handle sleeve, and the left handle is the clutch handle.


The torque produced by the motorcycle engine is very small. After the transmission deceleration, the torque output from the engine output shaft is still relatively small. Generally, a reduction device is set between the engine output shaft and the rear axle, so as to make more economic and reasonable use of engine power. The common transmission mode is chain drive, belt drive and shaft drive.

1. Chain drive

Chain transmission machinery parts less, simple structure, manufacturing and maintenance are very convenient.

Chain drive structure: the composition of the chain drive in addition to the chain, and the engine transmission auxiliary shaft (power output shaft) at the end of the drive sprocket and the driven sprocket on the rear wheel. The driven sprocket is bolted to the buffer body, which is connected to the rear wheel hub by a rubber buffer block. In this way, the power of changing gears in riding is transmitted flexibly through the buffer of rubber parts, avoiding damage to parts and improving riding comfort.

The distance from the center of the driving sprocket to the center of the driven sprocket of each type of motorcycle is basically a fixed value, and the adjustable range is limited, so the number of chain sections is a fixed value, one of which can be dismounted.

2. Belt transmission

Belt drive structure is simple, smooth transmission, low noise, easy to use and maintenance. When the rear wheel is overloaded, the belt can slip automatically to ensure that other parts are not damaged. But because it is to rely on friction to transfer power, so the belt transmission efficiency is low, short life.

3. Gear shaft transmission

The power output from the engine is transferred to the rear wheel by a gear shaft, which is called shaft drive

This transmission mode has the characteristics of compact structure, low noise, high strength, few faults and basically no maintenance. However, the manufacturing and installation accuracy of each part is higher, so it is difficult to manufacture and high cost.

Leave a comment

Your Name *

Email address *


Please note, comments must be approved before they are published.