While riding on pavement is all well and good, for many of us nothing can compare to getting down in the dirt. If you’re the type of motorcycle rider who longs for the roostertail and just can’t wait to strap your goggles to your face and get dirty on the trail or out on the track, then it’s very likely that you spend a lot of time thinking about the best dirt bike for your needs. After all, the trail is bumpy and rough and you rely on your bike to get you through it.
While there are tons of different companies out there to choose from, one of the enduring, perennial arguments in the dirt bike community surrounds the merit of two stroke engines and four stroke engines. In reality, your preference between these two is going to be entirely personal, as you can find many top riders on either style of bike. Most of the time people end up sticking with the variety of engine that they start riding dirt bikes with, but if you are just starting to get into dirt bike riding, it’s important to be aware of this polarizing debate.
What’s a “Stroke,” Anyway?
Obviously, before we can start talking about how your dirt bike engine affects your ride, it’s important to understand how engines work in the first place. Both types of engine, two stroke and four stroke, have a combustion cycle. This is when a piston moves within the cylinder in an up-and-down fashion. When the piston moves between the highest peak and the lowest point of its cycle, this is considered a “stroke.”
The overall process of gasoline and air being pulled into the piston, igniting, and expelling exhaust is called a combustion cycle. The entire cycle consists of four parts: the first is “intake.” This is when the piston moves downward and allows fuel and air to enter the chamber. Second, “compression” occurs. This is when the piston moves back up and the intake valve closes in order to compress the gas in the chamber. Third, “combustion” occurs when the spark plug sparks and ignites the gas in the chamber. Finally, the “exhaust” portion of the cycle is when the piston retreats back upward and the exhaust valve opens again.
2 Stroke vs 4 Stroke Dirt Bike
Both two stroke and four stroke engines have combustion cycles, but they go about the process a little differently. Where four stroke engines are concerned the piston strikes twice during each combustion cycle. There is one exhaust stroke and one compression stroke, followed by a returning stroke. Spark plugs fire every other revolution. As a result, the engine produces power every fourth stroke. These engines are more complex, and don’t require fuel and oil to be pre-mixed. They have a separate compartment for oil.
In comparison, two stroke engines are simpler. The entire cycle occurs with just a single piston stroke. When the piston stroke returns, fresh fuel enters the cylinder and exhaust escapes. In this type of engine, the spark plugs go off every single revolution. As opposed to power being produced every fourth stroke, power is produced in a two stroke engine every second stroke, as the name implies. You also need to premix oil with fuel for a two-stroke engine as there is no separate oil compartment.
Which is the Better Choice?
Again, there really is no “better” here. A lot depends on simple preference.
A four stroke engine is overall more efficient since it only takes fuel on every fourth stroke rather than every second stroke. A four stroke engine is also much quieter than a two stroke engine. Four stroke bikes do tend to last a bit longer since they run at a lower RPM overall as compared to their two stroke counterparts.
If you are concerned about the environment, four strokes are a bit more green in nature since a two stroke engine releases burnt oil into the air while a four stroke won’t. Four stroke engines also don’t require you to pre-mix your fuel with oil, owing to the separate oil compartment. They are also a bit more beginner-friendly as they offer a smoother ride. Four stroke bikes also need a little less maintenance, so if you’re not so much into the “tinkering” aspect of dirt biking you may prefer a four stroke.
That being said, four-strokes can be more expensive since they use more complex mechanics as compared to a two stroke engine. Two stroke engines also give you much more power with fewer CCs since they get more torque with lower RPM. Again, dirt bikes aren’t different from street bikes in that lower CCs means a lower price. The difference here is quite significant: a 125 CC two stroke bike is equal in power to a 250 CC four stroke bike. Two strokes are also more lightweight as compared to four strokes, given that the engine is far less complex and a bike’s engine is usually the heaviest component other than the gas tank when it’s full.
If you are trying to decide between a four stroke and two stroke engine, you need to prioritize. if cost is your number one issue, then you probably want to go with a two stroke engine given that you get a more powerful ride with far less CC and thus a much lower price tag.
If what you are mainly concerned about ease of riding, then you probably want to turn toward the four stroke engine. Dirt bikers who own both a two stroke and four stroke often say that the four stroke is much more reliable out on the trail, given that power is often less of an issue in the wild as compared to control. A four stroke engine requires much less shifting and breaking as compared to its two stroke counterpart. If you spend most of your time on the track, you may want to look more toward a two stroke given that you’ll be looking for that intense torque when you’re racing.
No matter what your engine preferences are, keep an eye out on the best dirt bike OEM to keep your ride comfortable and stylish.