Watch Through A Glass Cylinder Head As A Two-Stroke Dirt Bike Engine Works Its Magic

Photo: Petri Ranki/YouTube
Photo: Petri Ranki/YouTube

Mmm, two-stroke engines. You’ve seen them in weedwackers, but you probably haven’t realized how beautiful they are, offering tons of power in a very small package. Here’s a close-up look at the combustion chamber of such a beast, through the lens of a see-through cylinder head.

One of my friends has a fetish for two-stroke engines, and I totally understand why. The little single-cylinder thumpers make that beautiful “braaapidy brap brap” sound that we all subconsciously lust for.

But it’s not just the sound: two strokes can make gobs of power at hilariously low displacements, they’re super lightweight, and bone simple to work on. Heck, they don’t even have valves, which is why the plexiglass cylinder head below only houses a spark plug and nothing else. Have a look at the beauty in action below:

It turns out plexiglass threads aren’t very strong.

Anyway, if you’re curious to learn more about two-stroke engines—and you should be—the first half of this video does a very good job at explaining how these Mysterious But Awesome motors work:

But two-strokes aren’t perfect. They require a gas/oil mixture (usually around 20:1 or 30:1) to keep the moving parts lubricated since there’s no dedicated oil lubrication circuit, and even then, replacing the rings is a fairly regular occurrence.

Perhaps more importantly, two-stroke engines aren’t so good for the environment, in part because some of the fuel/air mixture shoots out the exhaust before ever undergoing combustion, and in part because there’s oil in the fuel, and burning oil tends to produce all sorts of Ice-Cap Melting gases.

Sr. Tech Editor, Jalopnik. Always interested in hearing from engineers—email me. Cars: Jeep J10 ('85), Jeep Cherokee ('79, '91, '92, '00), Jeep Grand Cherokee 5spd ('94), Chrysler Voyager Diesel ('94)

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Regarding emissions, these things are —dirty—. 30 minutes worth of use of a leaf-blower equated to the equivalent of driving a Ford Raptor for about 3800 miles to produce the same hydrocarbon output. Interesting article...