So you want to buy a quad eh? ATVs are fun and useful off-road vehicles that are relatively inexpensive and easy to maintain. To this day, though, the debate rages between supporters of the two stroke and the four stroke engines. What do you need to know when looking at purchasing an ATV?
Mechanically, the difference between a two stroke and a four stroke engine lies in how often the spark plugs fire. In a two stroke, it fires once with every revolution of the cam, while a four stroke only fires the plugs every other revolution of the cam. With everything being equal, a two stroke will have twice as many combustions as a four stroke, which causes it to produce much more energy with the same size engine. While this may make the two stroke engine the obviously superior choice, there are real-world drawbacks that may make you want to get a four stroke.
Because of the high heat that the two stroke engine develops due to the increased combustion frequency, oil needs to be added to the fuel as a cooling agent, which in turn causes it to produce a lot of smoke. This is why two stroke engines are being discontinued from production, and two stroke ATVs will no longer be available for purchase. Two stroke quads have been used in competitive motocross and high-speed racing, and that is what they are best suited for, because the great majority of their power is found at wide open throttle. This makes it impractical for use on rocky or muddy trails, where low-end torque is needed.
Think of the difference between these two engines as the difference between a 4-cylinder import and a big domestic V8 engine. The 4-cylinder can get a lot of power when revved high, whereas the V8 has loads of low-end torque that makes it so appealing for muscle car applications. In the end, it really depends on what you are going to be using your ATV for. In most cases, a four stroke quad will be perfect for most people, be it hunters, rock crawlers, farmers, or forest explorers.
To top it off, two stroke engines require much more frequent and involved maintenance and it consists of rebuilding the top end every so often. Four strokes, on the other hand, only require regular tune-ups and oil changes. Besides, you may have trouble finding a two stroke quad to buy in the near future, as they are a ‘dying breed’.