The BR500's four-stroke engine is five times cleaner than the standard two-stroke models.

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How does a four-stroke gasoline engine work?

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For years he had contemplated the inefficiencies of the traditional four-stroke Otto cycle engine (named for its 1876 developer, Nikolaus A. Otto).

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EcoMotors and Achates are developing two-stroke, opposed piston diesel engines while Pinnacle is working on a four-stroke opposed piston gasoline engine.

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