Valve Clearance

Valve clearance is the distance or gap between the cam and the top of the valve.  Because the engine has a rocker arm between the cam and valve, we measure this clearance as the distance between the cam and the rocker arm pad. We adjust the clearance by turning a set screw located at the end of the rocker arm.  The bottom of this screw effectively rests on top of the valve, so turning the screw clockwise moves the rocker arm up towards the cam (less clearance), and falls away (more clearance) if we turn the screw counter clockwise.We need to occasionally check and adjust valve clearance because the these components wear slightly with use and the clearance may fall out of the specified range resulting in extra wear (not enough clearance) or lost performance and noisy engine (too much clearance). 

cylinder block

         PISTONS

This picture shows the basic function of the pistons. Basically when the air and fuel mixture is compressed
it ignites and creates a spark for the spark plug. the crank shaft makes the pistons move up and down and also in a order.

CRANKSHAFT

 Receives oscillating motion from connecting rod and gives a rotary motion to the main shaft.It also drives the camshaft which actuate the valves of the engine.

 Cam Shaft

It takes driving force from crankshaft through gear train or chain and operates the inlet valve as well as exhaust valve with the help of cam followers, push rod and rocker arms.

Inlet Valve & Exhaust Valve

Inlet valve allow the fresh charge of air-fuel mixture to enter the cylinder bore. Exhaust valve permits the burnt gases to escape from the cylinder bore at proper timing.

Carburettor

It converts petrol in fine spray and mixes with air in proper ratio as per requirement of the engine.

Oil pump

The oil pump in an internal combustion engine circulates engine oil under pressure to the rotating bearings, the sliding pistons and the camshaft of the engine. This lubricates the bearings, allows the use of higher-capacity fluid bearings and also assists in cooling the engine.

The oil pressure generated in most engines should be about 10 psi per every 1000 revolutions per minute (rpm)

The oil pressure at the pump outlet, which is what opens the pressure relief valve, is simply the resistance to flow caused by the bearing clearances and restrictions.