Find Out Which Engine Type Is Best Before Choosing an ATV

Quad 4
2 Stroke ATV vs 4 Stroke ATV - What's the Difference?. (Richard Gerstner/Getty Images)

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 2 stroke and 4 stroke engines.

What you may not be familiar with is that the many facets of this debate are moot points.

Mechanical Differences Between 2 Stroke and 4 Stroke Engines

The biggest difference is the number of times the cylinder fires during a stroke.

A "stroke" comprises Intake, Compression, Combustion, and Exhaust. A 2 stroke engine will do this by moving the piston up and down 1 time, a 4 stroke engine will take 2 times.

In other words, a 2 stroke engine has a "power" cycle every time the piston moves up and down once, and a 4 stroke engine moves up and down twice to make power.

As you can imagine, you get more bang for the buck with a 2 stroke because you get more power with the same size cylinder.

    Misconceptions About the Difference in 2 Stroke vs 4 Stroke Engines

    There are a few common myths people use when comparing 2 and 4 stroke engines.

    The most common misconception is that 2 strokes have to have pre-mix (mixing gas with oil). This is only a matter of simplicity. Take a look at Caterpillars; they have huge oil sumps, they have oil pressure AND they are 2 stroke engines.

    Valves at the top of the cylinder head in 4 stroke vs reeds in cylinder walls on a 2 stroke is also a misnomer.

    Cruise ships have turbo diesel 2 strokes with poppet valves.

      Emissions and Maintenance

      People will also try to tell you that 2 stroke engines produce more emissions than 4 strokes. In general, this is true. But there have been huge advances in technology that has made 2 strokes able to run as clean as 4 strokes.

      Surrich/Orbital 2 stroke design on Mercury outboards is a good example.

      Maintenance is more frequent on 2 strokes because they fire more and run hotter. You can expect to re-do the heads every few seasons. Fortunately, 2 strokes are much simpler and therefore easier to work on.

        The Bottom Line: Power!

        So, what's the difference? About the only difference between 2 stroke engines and 4 stroke engines, besides the number of times they fire in a cycle, is the amount of power they can make given that everything else is equal. Because the 2 stroke fires more often than a 4 stroke (twice as much as a 4 stroke), it naturally results in more power.