This article/company are misrepresenting the truth. Once you add the carburetor, a starter (watch the video, they use a drill to start the engine, obviously real small engines have pull starters, which add weight.), the exhaust, intake manifold, etc. This engine is much heavier than 4 pounds.

This is almost the equivalent of me saying I've invented a 3 pound airplane, which is nothing but a carbon fiber tub. You just have to add wings, engines, cockpit, etc. etc.

It's a small engine, yes, that's nice. But don't blow it's carbon emissions up my ass and expect me to believe the hype.