Google Patents Four-stroke cycle internal combustion enginesĭownload PDF Info Publication number US2810373A US2810373A US502580A US50258055A US2810373A US 2810373 A US2810373 A US 2810373A US 502580 A US502580 A US 502580A US 50258055 A US50258055 A US 50258055A US 2810373 A US2810373 A US 2810373A Authority US United States Prior art keywords stroke piston cylinder valve internal combustion Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Google Patents US2810373A - Four-stroke cycle internal combustion engines This is why almost all two-wheelers, from big motorcycles to small scooters, use 4-stroke engines.US2810373A - Four-stroke cycle internal combustion engines But they provide stable power delivery, good fuel efficiency, cleaner emissions and more. And, many motorcycle enthusiasts continue to love 2-strokes for their punchy, breathtaking feeling of acceleration.Īs for 4-stroke engines, they run on gasoline without any oil mixed in and the piston goes up and down two times for every combustion cycle, hence it’s called a “4-stroke.” However, 4-stroke engines require valves for both the intake and exhaust that must operate with high precision, making this engine format more complex, heavier and other disadvantages. Today, Yamaha 2-stroke snowmobiles are used to traverse the icy cold environment of Russia, and our 2-stroke outboard engines are widely used across Africa for fishery.

Nonetheless, Yamaha 2-stroke products have a simple, lightweight construction and comparatively easy maintenance, and their high reliability keeps them popular in many regions. As of 2019, the only 2-stroke motorcycles Yamaha makes are for closed-course competition and some models for export.

However, concern for more environmentally friendly performance grew and 4-stroke engines are now the norm because they inherently have better fuel economy and less exhaust smoke. This are some reasons why 2-stroke engines have a long history of use on many different types of motorcycles. Because combustion takes place with each revolution of the crankshaft with a 2-stroke, this format puts out more power than a 4-stroke engine and the power has more instantaneous delivery. No intake or exhaust valves are used and instead, small holes called scavenging ports in the cylinder wall are used for drawing in air and expelling exhaust. It is called a “2-stroke” because just one up and down movement of the piston-the 2 strokes-performs the full cycle of intake, compression, combustion and exhaust. What’s the difference between 2-stroke and 4-stroke engines?įuel for a 2-stroke engine has a small amount of oil mixed into it.

Combustion 4 stroke