S.No.

Four stroke engine

Two stroke engine

1.It has one power stroke for every two revolutions of the crankshaft.1. It has one power stroke for each revolution of the crankshaft.
2.Heavy flywheel is required and engine runs unbalanced because turning moment on the crankshaft is not even due to one power stroke for every two revolutions of the crankshaft.2. Lighter flywheel is required and engine runs balanced because turning moment is more even due to one power stroke for each revolution of the crankshaft.
3.Engine is heavy3. Engine is light
4.Engine design is complicated due to valve mechanism.4. Engine design is simple due to absence of valve mechanism.
5.More cost.5. Less cost than 4 stroke.
6.Less mechanical efficiency due to more friction on many parts.6. More mechanical efficiency due to less friction on a few parts.
7.More output due to full fresh charge intake and full burnt gases exhaust.7. Less output due to mixing of fresh charge with the hot burnt gases.
8.Engine runs cooler.8. Engine runs hotter.
9.Engine is water cooled.9. Engine is air cooled.
10.Less fuel consumption and complete burning of fuel.10. More fuel consumption and fresh charge is mixed with exhaust gases.
11.Engine requires more space.11. Engine requires less space.
12.Complicated lubricating system.12. Simple lubricating system.
13.Less noise is created by engine.13. More noise is created by engine.
14.Engine consists of inlet and exhaust valve.14. Engine consists of inlet and exhaust ports.
15.More thermal efficiency.15. Less thermal efficiency.
16.It consumes less lubricating oil.16. It consumes more lubricating oil.
17.Less wear and tear of moving parts.17. More wear and tear of moving parts.
18.Used in cars, buses, trucks etc.18. Used in mopeds, scooters, motorcycles etc.