ADVANTAGES OF 4 STROKE ENGINE :-
More torque :- In general, 4 stroke engines always make extra torque than 2 stroke engine at low RPM. Although 2 stroked ones give higher torque at higher RPM but it has a lot to do with fuel efficiency.
More fuel efficiency :- 4 stroke engines have greater fuel efficiency than 2 stroke ones because fuel is consumed once every 4 strokes.
Less pollution :- As power is generated once every 4 strokes & also as no oil or lubricant is added to the fuel; 4 stroke engine produces less pollution.
More durability :- We all know that more the engine runs, quicker it wears out. 2 stroke engines are designed for high RPM. If an engine can go for 10000 rpm’s before it wears out; a 4 stroke engine with 100 rpm will run for 100 minutes than the other 2 stroke engine which has a higher rpm of 500 & will run for only 20 minutes.
No extra addition of oil :- Only the moving parts need lubrication intermediately. No extra oil or lubricant is added to fuel.
DISADVANTAGES OF 4 STROKE ENGINE :-
Complicated design :- A 4 stroke engine has complex valve mechanisms operated & controlled by gears & chain. Also there are many parts to worry about which makes it harder to troubleshoot.
Less powerful :- As power gets delivered once every 2 rotations of crankshaft(4 strokes), hence 4 stroke is less powerful.
Expensive :- A four stroke engine has much more parts than 2 stroke engine. So they often require repairs which leads to greater expense.
so, overall the 4-stroke engines have some minor disadvantages but a lots of advantages which are more relevant.