Two Stroke Engine Animation

Compression  StrokeI love simplicity. And a 2-stroke engine is that. It’s lighter and more powerful than its equivalent 4-stroke engine. Alas, it’s also not as efficient, not as reliable, and pollutes more than the 4-stroke. Hence, nowadays it’s rare in the world of road bikes.

Two-stroke engines operate in two strokes, instead of four, and this animation illustrates the two-stroke engine operation in conjunction with its expansion chamber showing the reflected pressure wave on the fuel charge.

1) Power/exhaust: This stroke occurs immediately after the detonation of the charge. The piston is forced down. After a certain point, the top of the piston passes the exhaust port, and most of the pressurized exhaust gases escape. As the piston continues down, it compresses the air/fuel/oil mixture in the crankcase. Once the top of the piston passes the intake port, the compressed charge enters the cylinder from the crankcase and any remaining exhaust is forced out.

2) Compression/intake: The air/fuel/oil mixture has entered the cylinder, and it begins to move up. This compresses the charge in the cylinder and decompresses the crankcase, pulling in more air, fuel, and oil from the carburetor. The compressed charge is detonated by the spark plug, and the cycle begins again. (Animation and indented material from

2 Stroke Animation

1 thought on “Two Stroke Engine Animation

  • Does anyone here know much about playing with the tuned pipe section of the exhaust for a 2 stroke?

    For example:
    1) I would like to know the maximum performace increase possible (for narrow band RPM) if the tuned section is adjusted
    2) ultimate idea is to make the tuned section “trombone” like so that adjustment could be made easier for different conditions (or really wild idea is making it adjustable on the fly 🙂

    I know it’s crazy, but any input would be welcome. I have an Aprilla 125 RS that I want to put under the knife (don’t worry, I’ll always keep the original pipe to transplant back on when my project doesn’t work) 😉

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