What is 4 stroke?

A 4 stroke engine, is one engine that has 4 "tasks" to do, which is:

1st Intake (mixing the air with fuel)

2nd Compression (compressing the air and fuel)

3rd Combustion (exploding the air and fuel with the engine's candles)

4th Exhaust (expelling the gases from the combustion)

A 2 stroke engine does 2 tasks at the same time, so it does the same as the 4stroke, but faster, and that's why 2 stroke have better acceleration, but also that's why you have to mix oil with the fuel (and sometimes they are a bit noise seeing that they get to high rpm's very fast, but a good exhaust should make the noise less noticeable)