Thursday, May 13, 2010



It is very important aspect for a rider to be more familiar with the bike and getting adjustable with different aspects of the same


There are two types of engine – Two Stroke and Four Stroke Engines

Both come under the category of “Internal Combustion (IC) Engine”. In two stroke engine, the working cycle is accomplished in two strokes of piston or one revolution of the crankshaft. This is attained by moving out the suction and compression processes in one stroke (or more in particular in an inward stroke), expansion and exhaust processes in the second stroke (or more in particular in an outward stroke).

In a four stroke engine, the working cycle is accomplished in four strokes of the piston or two revolutions of the crankshaft. This is attained by carrying out suction, compression, expansion and exhaust processes in each stroke. The four stroke Petrol Engine Cycle also recognized as Otto Cycle requires four strokes of operation in the engine cylinder. The four strokes of a petrol engine sucking fuel-air mixture (petrol mixed with in proportion quantity of air in the carburetor known as charge) are expressed below.

Ø Suction or Charge Stroke: In this stroke, the inlet valve opens and pure air is sucked into the cylinder as piston moves downwards from the Top dead centre (TDC). It maintains till the piston attained its Bottom dead centre (BDC).

Ø Compression Stroke: In this stroke, both the valves are closed and the air is compressed as the piston moves upwards from BDC to TDC. As a result of this compression, the pressure and temperature of the air increases considerably. This finishes one revolution of the crank shaft.

Ø Expansion or Working Stroke: Shortly after the piston reaches TDC (during the compression stroke), fuel oil is injected in form of very fine spray in engine cylinder, all the way through the nozzle, known as fuel injection valve. At this moment, temperature of the compressed air is satisfactorily high to ignite the fuel. It suddenly increases the pressure and temperature of the products of combustion. The fuel oil incessantly injected for a fraction of the revolution. The fuel oil is assumed to be burnt at constant pressure. Due to increased pressure, the piston is pushed down with a immense force. The hot burnt gases expand due to high speed of the piston. During this expansion, some of the heat energy is distorted into mechanical work. It may be noted that during this working stroke, both the valves are closed and the piston moves from TDC to BDC.

Ø Exhaust Stroke: In this stroke, the exhaust valve is open as the piston moves from BDC to TDC. This movement of the piston pushes out the products of the combustion from the engine cylinder all the way through the exhaust valve into the atmosphere. This completes the cycle and the engine cylinder is ready to suck the fresh air again.It will be interesting to know that from the thermodynamic point of view, there is no difference between two-stroke and four-stroke cycle engine. The difference is purely mechanical.

Today all the major IC Engines of the world are running on the four stroke cycle.


The engine converts the hotheaded energy to mechanical energy, through the reciprocating motion to rotary motion. The power urbanized from rotary motion is forbidden by various systems in a bike. This system is well-known as the Transmission. The Transmission comprises of the clutch, gear-box & final-drive chain all the way upto driving wheel.

The clutch is a very essential “Link” in the transmission of bike. Its primary use is to permit the rider to engage and disengage the engine from wheels. It also takes up most of the load and vibrations from engine and does not allow it to pass into the rest of the transmission.

After the clutch comes to the gear-box, a box having set of gears, it allows the rider to use the finest amount of power from the engine as and how essential. The main function of the gear-box is to reduce strain on the engine by supplying capable power at required time. For Instance, the first gear is lowest and most sensitive gear, which helps in moving of a stationary bike without putting excessive load onto the engine. On the other, the use of second gear requires relatively more acceleration and gives more strain on the engine and the clutch. A lower gear serves two functions. They serve as brake and also improve acceleration when required. For instance, while going downward on a lower gear provides “Braking Power” and during rising provides extra power.

The power transmission is by the way of two chains. The primary chain is mutually with this in the clutch case on the L.H.S. of the bike and runs in an oil-bath. The final or drive chain connects the gear-box to the drive-sprocket of the rear wheel. The drive-sprocket is attached with the brake drum, which in turn is fit into the rear hub. There are four rubber blocks rigid between the drive-sprocket/brake-drum and the hub of the rear wheel, which act as efficient dampers, absorbing practically all the shocks of power and transmission units and have a very encouraging influence on the life of chain as well as very important engine parts.


The main components of an electrical system in the bike are the Battery, Alternator/Dynamo/ Generator/Magneto and Ignition/High-Tension Coil(s). The main occupation of the system is to provide ignition in the form of a spark to the compressed air with fuel mixture in the cylinder. A battery gives either 6 volts or 12 volts current. But a voltage thousands times higher is needed to create a spark from the spark plug, which can ignite the air with fuel mixture. It’s the high tension coil (Ignition coil) which improves low voltage current of the battery and provides upto 30,000 volts to the spark plug. A small spark is makes at the distributor, which is converted to a high voltage current, which flows to the spark plug and finally ignites the air with fuel mixture. A contact breaker and rotor, inside the distributor, make sure correct series of current to the plug while a condenser attached to the contact breaker serves as a capacitor that reduces the damage to the contact breaker. One more part, which is at the heart of the electrical system, is the Alternator/Dynamo/Generator/ Magneto. This provides a charge to the battery by generating a current. As the generator output increases with the engine speed a control unit (Cut-out/Regulator) is presented to control the output. This unit stops the damage to the generator unit and protects the battery from over charging/discharging. The stored energy of battery is used for different purposes such as: ignition, horn, lights etc.

To keep the standard energy of the battery it wants periodical maintenance like check up of specific gravity, cleaning of terminals, applying a thin film of petroleum jelly or pure Vaseline (not grease) to keep terminals and connections from corrosion and sulphation etc.


There are two different types of brakes used in bikes, namely: Drum Brakes & Disk Brakes. The Drum Brake has an aluminum/steel/iron drum to which the wheel is attached. The drum and wheel rotate together. The brake shoe plate is bolted on to the chassis and inside the drum lie the brake shoes, which have brake liners on them. The brake liners are either engrossed or casted onto the brake shoes.

When the brake pedal is dejected, a cam (placed between the brake shoes) rotates such that the brake shoes move towards the drum. When the brake shoes grip the rotating drum, the rotating wheel changes itself by lock or stop.

The Disk Brake has a metal disk instead of a drum fitted to the wheel and the calipers are bolted on to the chassis/shock-absorber pipe. The calipers have pistons and brake pads. The disk brake has to be operated hydraulically. The brake fluid and the actuating cylinder (brake-oil sump) are fitted on the handle bar of the bike. When the brake lever is hard-pressed a non return brake valve operates and sends the brake fluids to the caliper and the piston, the caliper operates thereby forcing the brake pads to move towards the disk and produce the friction which allows you to slow down or stop.

The usual arrangement on a good bike is front disk brake and rear drum brake.


The Front suspension consists of a telescopic fork with hydraulic dampers. It is the straight slider type with two cylindrical coil springs. Steel cover tubes protect the suspension elements. The rear suspension operates on a circular path. The pivoted rear swing arm is sprung by two cylindrical coil springs and fitted with hydraulic dampers. The suspension dampers are protected by chromium plated steel covers.


The Tyres have two functions. Firstly, they are air-filled cushions that absorb most of the shocks caused by riding on bad roads. Therefore they diminish the effect of the shocks. Secondly, the tyres grip the road to provide good traction. Good traction allows the bike to accelerate, brake and make turns without skidding. There are two types of tyres available, the inner tube type and the tubeless type.

In the inner tube type tyre, both the tube and tyre are mounted on the rim. The tube is like a hollow rubber doughnut. It is inflated with air after it is installed inside the tyre and the tyre is put on the wheel rim. The increase causes the tyre to resist any change of shape.

The tubeless type tyre does not have an inner tube. As a substitute, the tubeless tire is directly mounted on the wheel rim so that the air is preserve between the rim and the tyre.

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