Activities Hobbies The Great ATV Engine Debate 2-Stroke vs. 4-Stroke Share PINTEREST Email Print 2 Stroke ATV vs 4 Stroke ATV - What's the Difference?. (Richard Gerstner/Getty Images) Hobbies Cars & Motorcycles ATVs & Off Road Cars Motorcycles Used Cars Trucks Public Transportation Contests Couponing Freebies Frugal Living Fine Arts & Crafts Astrology Card Games & Gambling Playing Music Learn More By Matt Finley Matt Finley Matt Finley is a sports writer specializing in off-road recreation. He has covered ATV, 4x4, motocross, and motorcycles for outlets including ATV magazine, MX Affiliate magazine, and ATV Source. Learn about our Editorial Process Updated on 07/11/18 If you've been around ATVs, dirt bikes, or other small performance engines for any length of time, you're probably familiar with the age-old debate between two-stroke and four-stroke engines. What you may not be familiar with is that many facets of this debate are moot points. The Mechanics The biggest difference between the two engine types is the number of times the cylinder fires during a single phase of the engine's power cycle, known as the stroke. This cycle is comprised of the intake of gas/air, its compression, followed by the combustion that makes the vehicle go, and then dissipation of the exhaust through the exhaust pipes. A two-stroke engine will do this by moving the piston up and down one time, while a four-stroke engine will take two times to complete a stroke. This naturally affects the engine's power, which we'll get to in a minute. Common Myths There are several misconceptions about how these engines work and the ways in which that affects their efficiency. The most confusing concerns engine lubrication. All engines need to be lubricated in order to run, otherwise their metal parts will wear on each other and eventually stop working. This is why one of the most important things you can do to maintain the health and longevity of your vehicle is check its oil on a regular basis. Four-stroke engines are lubricated by holding oil in a sump pump. Oil is distributed from this sump pump through either a splashing action, in which the movement of the crankshaft rotating in and out of the oil in the sump "splashes" oil to the engine's components, or through pressurized lubrication provided by the pump. Two-stroke engines on the other hand cannot use a sump pump lubrication system because their inlet and outlet (exhaust) bores are located on the sides of the cylinder—the bores would become blocked. Instead, oil and gasoline are either mixed together before being poured into the fuel tank, or the two-stroke utilizes some kind of oil injection system. If you use a high-quality two-stroke oil, there is no reason why your ATV's two-stroke engine shouldn't last as long as a four-stroke. People will also try to tell you that two-stroke engines produce more emissions than four strokes. In general, this is true. But huge advances in technology have made two-strokes able to run nearly as cleanly as four-strokes. Two-stroke engines do require more maintenance because they fire more and run hotter. You can expect to re-do the heads every few seasons. Fortunately, two-stroke engines are much simpler and therefore easier to work on. The Bottom Line: Power! About the only difference between two-stroke and four-stroke engines, besides the number of times they fire in a cycle, is the amount of power they can generate, given that everything else is equal. A two-stroke engine fires every time the piston moves up and down once, while a four-stroke engine fires once very two strokes. As you can imagine, you get more bang for your buck with a two-stroke, which generates more power with the same-sized cylinder.