What are "two-stroke engines" and why do they generate so much pollution?

What are "two-stroke engines" and why do they generate so much pollution?

Terry Tamminen (Author & Environmental Policy Advisor) gives expert video advice on: What percentage of the world's "carbon emissions" come from the United States?; Do I have to choose between a healthy economy and a healthy environment? and more...

Engines typically come in what's called four-stroke or two-stroke. That's just the number of movements of the piston inside the engine. Without getting into the details of how engines work, four-strokes are designed to operate more cleanly than two-strokes. Two-strokes lose as much as half of the oil or gasoline that's put into the engine, which is discharged as air polution.