A key decision when it comes to gas-powered dirt bikes is whether to pick 4 stroke dirt bikes or 2 stroke dirt bike. And it’s a difficult question especially if you are not familiar with the difference between 2 stroke and 4 stroke dirt bikes.
Now, in this analysis article, I will divulge the main difference between 2 stroke and 4 stroke dirt bikes and the impact of choosing one over the other could have on your dirt biking adventure.
Let’s blow the whistle on this latest 2 stroke vs 4 stroke dirt bike battle.
And first, the basic questions…
What Are Strokes On A Dirt Bike?
Usually, strokes refer to a complete travel of their pistons along the cylinder regardless of the direction. For example, from the TDC (top dead center) to the furthest down a piston can travel.
Each stroke has a role to play in order to generate the power required to run the bike.
Then, the number differs. In short, 2 stroke engines need 2 sequences while 4 stroke engines will, of course, need 4 strokes hence the debate two stroke vs four stroke.
Next, I will explain what each of the strokes does.
What Does 4 Strokes Mean On A Dirt Bike?
In 4-stroke dirt bike engines, the cycle consists of four strokes of their piston: Intake, compression, power, and lastly exhaust.
Notably, the power stroke stage is the major source of an engine’s torque and subsequent power.
The engines spark plug fires only once every 2 revolutions in 4-stroke engines.
Usually, what you see coming out via the bike’s exhaust valve is the burned gas as pushed out during the exhaust stroke.
Moving on, the 4 strokes design is somewhat complex as it’s reliant on a valve mechanism, itself operated via a form of gear/chain arrangement to run the cycles.
On engine conditioning, 4-stroke engines are typically lubricated by oil held in their sump pump with the oil being distributed from the sump pump via a splashing action.
Alternatively, the oil is spread through pressure-based lubrication created by the pump.
What Does 2 Stroke Mean On A Dirt Bike?
Two strokes engines use 2 strokes to run the 4 processes so every two processes are merged into one action.
When we come to lubrication, 2-stroke engines cannot use the sump pump system since the inlet and outlet bores are found on the walls of the cylinder and may easily become blocked.
Instead, you have to mix oil and gasoline together before pouring the mixture into the bike’s fuel tank.
There are also instances where two-stroke engines work with some form of an oil injection system.
On firing, two-stroke engines fire each time a piston moves up/down.
And as we have seen, 2 stroke engines replace the valve system with ports so the design is far much simpler.
What Is A 4 Stroke Dirt Bike?
When rated against 2-strokers, 4 stroke engines involve a tidier way of movement of charge and exhaust. Four strokes burn fuel more efficiently than two strokes now that 2 stroke engines can’t burn the entire fuel.
That 4-strokes get through reduced fuel makes them favorable in those terrains where gas stations are very scattered.
Gear selection is also less of a bother as the bike pulls almost any gear depending on the conditions and speed needs.
What Is A 2 Stroke Dirt Bike?
Maintaining the same tone, 2 stroke dirt bikes use the previously discussed two-stroke engines. These engines simplistic design makes them lighter than their 4-stroke peers and subsequently easier to lift and bring down.
But these bikes need frequent shifting making them more difficult than 4-stroke bikes to control.
Traditionally, two-stroke engines take in more fuel and generate more emissions than the ‘competing’ four strokes.
Its ,however, important to note that due to recent advances in motor technology, two-strokes dirt bikes can now run almost as neatly as four-strokes.
2 Stroke Vs 4 Stroke Power
Since a four stroke dirt bike produces power with each stroke in the cycle and fires every two revolutions, there’s a steadier and a generally more predictable delivery of power. This explains their being more manageable.
The other notable reason is that 4-stroke engines powerband is known to be significantly smoother making them easier to ride for starters.
This controlled power also means they don’t need hefty effort to ride, yet another factor in their popularity among beginners.
In summary, the 4 stroke’s user-friendly power makes it a champion in difficult conditions that usually need great traction. For example, a 4-stroke rider will grin on ruts and hard pack dirt racing.
In comparison, two-stroke engines can emit twice the level of power a same-size four-stroke engine would.
That’s simply because it fires every revolution while the four-stroke fires every two rotations.
The engines will also rev up to a higher rpm helping produce higher ranges of riding power compared to 4-strokers.
Sandy, loamy, and loose dirt are some zones where the 2 stroke outshines the four strokes.
Exhaust is pushed out via an inefficient process christened scavenging because the power and exhaust strokes are merged.
What’s Faster 2 Stroke Or 4 Stroke?
Since 2 strokes have more power than their rivals, it follows that they smash through speed barriers better than 4 strokes.
While a 220cc dirt bike is greater size-wise than 110cc and many actually think it’s twice as powerful, the 110cc 2-stroke dirt bike will outgun a 220cc 4-stroke.
And that’s always true: 2-stroke bikes typically have a significantly higher power than their 4-stroke counterparts with equal engine displacement.
So in short, 2 strokes will outpace it a 4 stroke bike of an equivalent displacement.
2 Stroke Vs 4 Stroke Dirt Bike Maintenance
As I have repeatedly said, two-stroke engines have a simpler and more straightforward engineering. For this reason, the manufacturing and the components are less complicated than their chief competition. This means you have fewer parts to worry about.
There are, however, several issues to note here:
- The Issue Of Mixing Gas & Oil
Well, two-stroke engine uses a mixture of gasoline and recommended two-stroke engine oil in their fuel tank.
The combination can potentially clog the carburetor if not prepared well or if allowed to sit for long (and become stale).
- The Issue Of Inadequate Cooling Off Time
Additionally, these engines tend to wear out faster because they experience explosions at twice the frequency in four-stroke engines in the chamber.
This means they have an inadequate cooling off time in between explosions. Well, it’s true that recent models are performing better but the gap still exists.
- The Issue Of Poor Exhaust Scavenging
Do you still remember about the poor exhaust scavenging that we talked about earlier on?
If yes, the problem is that this could add to the unhealthy carbon buildup in the engine causing wearing.
- The Issue Of Stressed Engine
There’s also the higher horse power/weight ratio and the resultant high revving of the engine which is sometimes highly stressing to these engines.
Two-stroke engines have fewer parts but are prone to quicker wear. You may, therefore, need to rebuild your 2 strokes quite often.
Let’s now contrast with 4-stroke engines.
Here is why:
- The Advantage Of A Dedicated Engine System
Four stroke engines have a specialized lubricating system and superb fuel burning efficiency.
- Balanced Power
Four stroke engines steady power transmission and won’t stress the engines as much as in two-stroke engines.
These engines are more durable but tougher and expensive to work on.
Summary Maintenance Schedule:
For both bikes:
- Check air filters and tranny oil.
- For four strokes add:
- Check crankcase oil filters.
- Adjust the valves periodically
We have looked at the difference between 2 stroke and 4 stroke dirt bikes from various perspectives so let’s find the winner.
Two stroke dirt bikes have poor fuel consumption, more harmful emissions, poor combustion, and more noise.
But they have more torque and know how to crank up the pace when needed.
Conversely, 4 stroke engines have improved fuel efficiency and are environmentally friendlier.
The engines are also generally longer lasting and easier to handle.
Their major downside is the less power, confusing design, and expensive repairs whenever needed.
Unsurprisingly, they come at a higher price.
And so the winner is…
I am sorry this could be an anti-climax but it’s all about personal preferences as each has its own wins and losses!
Having said that, make a wise choice!
Alex Mwangi is the creator of Outdoor Right and an outdoor enthusiast. During his free time he enjoys riding his road bike or traveling the world looking for his next adventure.