Motorcycle engines: device, operating principle, technical characteristics

Novice drivers sometimes think that the most important quality that motorcycle engines have is the amount of horsepower, and believe that the tool will ride well, only having a capacity of more than one hundred forces. However, in addition to this indicator, there are many characteristics that affect the quality of the motor.

Types of Motorcycle Engines

There are two-stroke and four-stroke engines, the principle of operation of which is somewhat different.

Also on motorcycles set a different number of cylinders.

In addition to the native carburetor engine, you can often find injector units. And if the first kind of motorcyclists are accustomed to correct themselves, then the injector engine with a direct injection system with their own hands to repair is already problematic. For a long time already produce diesel motorcycles and even with an electric motor. The article will consider the characteristics of a carburetor-type motorcycle engine.

How the engine works

In the engine cylinders, the thermal energy of the combustion fuel is converted into mechanical work. In this case, the piston moving due to the gas pressure causes the crankshaft to rotate through the crank mechanism. This mechanism consists of a crankshaft, a connecting rod, a piston with rings, a piston pin, a cylinder.

Differences in design lead to different work of two- and four-stroke engines.

Four-stroke engine

Such motors have a duty cycle of four strokes of the piston and two turns of the crankshaft. The scheme of the engine clearly shows the device of the piston engine and its working process.

1. At the inlet, the piston descends from the top dead center, sucking the mixture through the open valve.

2. When compressed, the piston, rising from the bottom dead center, compresses the mixture.

3. During the working stroke, the mixture, ignited by an electric candle, burns, and the gases move the piston down.

4. At release the piston, rising, pushes the exhausted gases through an open outlet valve. When the top dead center is reached again, the exhaust valve closes and everything is repeated anew.

Advantages of four-stroke are:

• reliability;

• Economy;

• Less harmful exhaust;

• Small noise;

• Oil with gasoline is not pre-mixed.

The construction of this type can be displayed by the following motor circuit.

Two-stroke engine

The volume of the motor of this type of motorcycle, as a rule, is smaller, and the working cycle takes one turn. In addition, it has no intake and exhaust valves. This work reproduces the piston itself, which opens and closes channels and windows on a cylindrical mirror. Also, during gas exchange, a crankcase is used.

The advantages of this engine are:

• With the same volume of the cylinder, it has a power that exceeds the four-stroke in 1.5-1.8 times;

• Has no camshaft and valve system;

• The manufacture is cheaper.

Cylinders and workflow in them

The working process of one and the other engine occurs in the cylinder.

The piston moves here along a cylindrical mirror or plug-in sleeve. If air cooling works, then the cylindrical shirts have ribs, and with water cooling - internal cavities.

Crankshaft through the connecting rod perceives the movement of the piston, transforming it into rotational, and then transmitting the torque of the transmission. Also, the gas distributing mechanism, the pump, the generator and the balancing shafts begin to work. The crankshaft has one or more elbows depending on the number of cylinders.

In the four-stroke engine, so that the cylinder is better filled with the mixture, the intake starts even before the piston reaches the top dead center, and ends after the bottom dead center passes through it.

Cleaning it begins before reaching the bottom dead center, and expelled the exhaust gases when the piston moves to the top dead center. After that, the exhaust valve closes so that the gases leave the cylinder.

The following types of gas distribution mechanism are used on the motor of this type:

• OHV;

• OHC;

• DOHC.

The last type has a minimum number of elements, so that the crankshaft can rotate faster. Therefore, the DOHC is becoming more widespread.

Four-stroke engines have a more complex design than two-stroke engines, as they have a lubrication system and a gas distribution mechanism that is not available for two-stroke engines. Nevertheless, they began to spread widely because of the economy and less harmful impact on the environment.

Motorcycle engines are usually one-, two- and four-cylinder. But there are aggregates with three, six and ten cylinders. Cylinders in this case are in-line - longitudinal or transversal, horizontal opposites, V-shaped and L-shaped. The working volume of motors usually have not more than one and a half thousand cubes of these motorcycles. Engine power - from one hundred and fifty to one hundred and eighty horsepower.

Engine oil

Lubrication is necessary to ensure that there is no excessive friction between the motor parts. It is realized with the help of motor oils having a stable structure from high temperatures and low viscosity at low rates. In addition, they do not form a deposit, they are not aggressive to plastic and rubber parts.

Oils are mineral, semi-synthetic and synthetic. Semisynthetics and synthetics are more expensive, but these species prefer more, since it is believed that they are more useful for the engine. For two-stroke and four-stroke, different types of oils are used. Also they differ in the degree of forcing.

"Wet" and "dry" crankcase

Four-stroke engines use three ways of oil supply:

• Samotec;

• Spraying;

• Feed under pressure.

And most rubbing couples are lubricated under pressure from an oil pump. But there are also those that are lubricated by the oil mist formed by the sprinkling of the crank mechanism, as well as the parts to which oil flows down channels and gutters. In this case, the oil pan serves as a reservoir. It is called "wet" in this case.

In other motorcycles, a dry crankcase system is provided, where oil is pumped into the tank in one section and the other is supplied under pressure to the friction points.

In the spirit-pressure lubricant is oil, which is in the vapor of fuel. It is mixed with gasoline beforehand, or in the inlet pipe it is fed by a metering pump. This last type was called the "separate lubrication system". It is especially common on foreign motors. In Russia, the system is included in the engine of the motorcycle "Izh Planet 5" and "ZiD 200 Courier".

Cooling system

When fuel in the engine burns, heat is generated, from which almost thirty-five percent goes to useful work, and the rest is dissipated. In this case, if the process is inefficient, the parts in the cylinder overheat, which can lead to jamming and damage. To prevent this from happening, a cooling system is used, which is air and liquid depending on the type of motor.

Air cooling system

In this system, the parts are cooled by counter-air. Sometimes, for better work of the surface of the cylinder, its heads are made ribbed. Sometimes forced cooling is used with a fan with a mechanical or electric drive. The four-stroke ones also carefully cool the oil, for which the crankcase surface is enlarged and special radiators are installed.

Liquid cooling system

The option is similar to what is installed on cars. The coolant here is antifreeze, which is low-freezing (from minus forty to minus sixty degrees Celsius) and high-boiling (from one hundred and twenty to one hundred and thirty degrees Celsius). In addition, antifreeze is achieved anti-corrosion and lubricating effect. Pure water in this capacity can not be used.

Overheating of the cooling system can be caused by overloading or contamination of surfaces that remove heat. Also, it can break down the individual elements, because of which the liquid will flow out. Therefore, the work of cooling must be constantly monitored.

Supply system

As fuel for carburetor motorcycles use gasoline, octane number of which is not lower than 93.

Motorcycle engines have a power system, which includes a fuel tank, a crane, a filter, an air filter and a carburetor. Gasoline is in the tank, which in most cases is installed above the motor in order to gravity flow into the carburettor. In other cases, it can be fed using a special pump or a vacuum drive. The latter can be found on two-stroke.

In the fuel tank there is a lid with a special hole, where air enters. In many foreign motorcycles, however, air gets through coal tanks. And some have a lock on the lid.

Thanks to the fuel valve, fuel leakage is prevented.

Air enters the carburetor through the air filter. The filter is of three types.

1. In a compact-oil type, air enters the center, rotates 180 degrees and passes into the filter. At the same time, it is cleaned by turning the flow, where the heavy particles settle in the oil. Such a filter is equipped with a motorcycle engine "Ural" and "Izh". However, other types are used abroad, paper and foam rubber.

2. Paper filters are disposable. They must be changed on every maintenance.

3. Foam filters are reusable - they can be washed and re-impregnated with oil.

Sports motorcycles, which have an engine of 250 cubes and above, today have a system of so-called "direct intake", when the intake of air comes from the front of the fairing, so that the filling of cylinders at high speeds increases.

Carburetor and its types

This device prepares and doses the air-fuel mixture, which after it passes into the cylinder. Modern carburetors come in three forms:

• Spools;

• Constant rarefaction;

• Registered.

All domestic engines, as well as the motor of the motorcycle "Ural" have spool carburettors. The only exception is Ural-Vostok, on which a carburettor of constant rarefaction is installed.

In the spool carburetor, the gas knob is connected to the spool. Through the influence on it, the air entering the motor is regulated. A conical needle is connected to the spool, which enters the atomizer. When it changes, the mixture is enriched or impoverished. A fuel jet is installed on the spray gun. And together all the elements constitute a dosing system.

In carburetors of constant rarefaction, the movement of the handle of the gas is transferred to the throttle, which is closer to the exit from the carburetor. Air in the chamber above the spool interacts with the mixing carburetor chamber. So it turns out that the movement of the spool is regulated by the discharge in the intake tract.

Register carburettors, which are equipped with many foreign single-cylinder four-stroke, for example Honda engines, combine the two previous types. There are two mixing chambers in it, where in one the spool is driven from the handle, and in the other - from the vacuum in the mixing chamber.

Running

In order to start a cold engine, an enriched mixture is needed. In the chamber of some carburetors, there is a float drowner for this. When its rod is pressed, the fuel level in the chamber rises sharply to a level higher than the permissible level. Because of this, the fuel begins to flow into the intake manifold. And part of the fuel flows out. For some time now, however, carburettor designs are designed in such a way that the pairs do not fall outside. Such designs assume the use of a concentration mixture, which is an air dam or another fuel channel. It is used instead of the utopian.

Recently, four-stroke motorcycle engines often have a fuel injection system on electric control. It consists of a fuel pump with an electric drive, a battery, electromagnetic injectors, an electronic control unit, which is connected to various sensors, a distribution pipeline.

There are also systems of motor control, where the adjustment of power and ignition systems are combined, which increases the economy and at the same time the capacity of the unit.

The main malfunction of the power system, because of which it may be necessary to repair a motorcycle engine, is the reduction or even shutdown of fuel supply due to clogging. To avoid this, a fuel filter is used. In addition, it is necessary to monitor the condition of the air filter and the tightness of the nozzles.

Release system

The exhaust system consists of a cylindrical discharge channel, a branch pipe and a silencer. In two-stroke models, the economy and power depend directly on the size and shape of the system components. Therefore, exhaust systems for each cylinder are used for them individually. They have a resonator, a branch pipe and a silencing attachment.

In four-stroke exhaust valves control the gas distribution system, so the resonance in them a special role does not play. In them, usually all the branches are reduced to a single silencer.

On some motorcycles, emissions are equipped with catalytic converters that reduce emissions (they are installed, for example, on engines of Honda and other Japanese manufacturers). Such devices were developed due to stricter requirements for exhaust gases in the EU countries, the USA and Japan. In order to prevent a backward ejection of the mixture from the cylinders at idle and a small rotation of the crankshaft, in the exhaust systems of many motorcycles special power valves are provided.