4-strokes also take a much longer time to break-in, being ringed engines, as opposed to ABC. ABC engines, you can run a couple of tanks through them in a rich 2-cycle and they are good to fly. 4-stroke ringed engines need a good bit of slobbering rich running, then rich running in the air. I typically run 1/2 gallon of fuel with extra castor in smaller engines (.72 & less) and a gallon in larger 4-strokes on my bench, then fly. A Saito will take 2 gallons plus to be really running great. My Magnums seem to take the same time or maybe slightly less to break-in.

There are advantages to both and disadvantages. I like my screaming 2-strokes, but there is something nice about a deep throated 4 banger turning a big prop.