The 4-stroke engine cycle consists of the intake stroke, compression stroke, power/combustion stroke, and exhaust stroke within one revolution of the crankshaft. During the intake stroke, the intake valve opens and the piston travels down to allow an air-fuel mixture into the cylinder. In the compression stroke, both valves are closed and the piston compresses the mixture. The spark plug then ignites the compressed mixture in the power stroke to force the piston down. Finally, in the exhaust stroke the exhaust valve opens and the piston pushes out the exhaust gases. The key components of a 4-stroke engine include the intake and exhaust valves, piston, spark plug, crankshaft, and camshaft.

2. 4 Stroke Petrol Engine

3. Engine displacement

4.  The 4 Stroke engine cycle consist of these:
1) Intake 180degree
2) Compression 180 degree
3) Power/ Combustion 180 degree
4) Exhaust 180 degree
 Total engine revolution 720 degree

5. The Intake Stroke
consist of the piston
travelling down.
Intake valves are
open to allow
Air/Fuel mixture to
come into the
combustion chamber.
Intake

6. It is an electrical
device that fits into
the cylinder head and
ignites air fuel
mixtures.
Spark plugs

7. Inlet valve
open
Piston down
INTAKE STROKE

8. Inlet valve
open
Piston down
INTAKE STROKE
Fuel in

9. Compression stroke consist of
the piston travelling back up.
Both intake and exhaust valves
are closed
Air fuel mixture is now being
compressed
Compression

10. COMPRESSION STROKE
Piston up

11. Inlet valve
closed
COMPRESSION STROKE
Piston up

12. The piston is now at the TDC
Spark plug ignites, creating a spark that ignites the compressed air fuel
mixture.
Explosion is created and the piston is forced back down.
Hence the Power stroke
Both valves are still closed

13. Inlet valve
closed Exhaust
valve
closed

14. Inlet valve
closed

15. Exhaust stroke the
piston is travelling up
Exhaust valve is open
Intake valve is Closed
Exhaust gases being
pushed out by piston
Exhaust

16. Inlet valve
closed
Exhaust valve
open
Piston up
Exhaust gases
out

17. Inlet valve
open
INTAKE STROKE
Exhaust valve
closed

19. Basic Components of Four-Stroke
Engines
Intake Valve
Valve Cover
Intake Port
Head
Coolant
Engine Block
Oil Pan
Oil Sump
Crankshaft
Camshaft
Exhaust Valve
Spark Plug
Exhaust Port
Piston
Connecting Rod
Rod Bearings