Bread and butter engines on most of your discount store or "big box" retailers' mowers.
Junk if you ask me. B&S has more or less pioneered the term "planned obsolescense" with these engines. Well, them and the Tecumseh competiton. The latter that consume a profuse amount of oil right out of the box and run so lean with their fixed jet carbs that most people throw them away before they get broke in. A torch tip cleaner or pin drill can fix 'em, but most end up getting scrapped before someone with any knowledge can get to them and make them run right.