A lot of them are 2-stroke engines, which burn a mixture of gasoline and oil. Usually badly tuned with poor fuel/air metering. They pollute like crazy. The US

A lot of them are 2-stroke engines, which burn a mixture of gasoline and oil. Usually badly tuned with poor fuel/air metering. They pollute like crazy. The US EPA has not yet banned 2-strokes, but emissions on them have been tightened, and there are different allowances[0] for 2-stroke engines with aftertreatment technology vs. without. 2-strokes are commonly used in lawn equipment, chain-saws, snow blowers, jet-skis, etc. And famously in the East German Trabant 601 automobile (called "little stinker" by the West Germans) [0] https://www.ecfr.gov/current/title-40/chapter-I/subchapter-U/part-1054#p-1054.245(c) https://www.ecfr.gov/current/title-40/chapter-I/subchapter-U...