This website specifically talks about 4 stroke dirt bike engines and how they work.This website tells me how far back 4 stroke engines went, which was 10 years. Before that it was just 2 stroke and nothing else.This website also talks about how 4 stroke dirt bike engines last longer in many ways. For example 4 stroke dirt bikes don’t rev as high as two strokes which stop many thing like the chain. When a 2 stroke is running there is a better chance of it breaking because it revs so high which makes the motor super hot, which could burn off the chain. I think this website will help me learn about specifically 4 stroke dirt bikes and will come in handy when I am researching or testing a 4 stroke.

This is the website