As you select your dirt bike for your adventures, you might be intrigued with the difference between a 2 stroke vs 4 stroke dirt bike. However, you might not get your ideal type without a proper assessment on the essentials of each.
There are lots of factors involved when choosing your ideal dirt bike which will further be elaborated by this guide. For beginner purposes, we will present first a tabulated summary on the essential features of a two stroke vs four stroke dirt bike below:
| Features | 2-stroke engine | 4-stroke engine |
| Engine size | Smaller engine size | Larger engine size |
| Design | Simple engine design | Complex design due to more parts |
| Power requirement | More power requirement, fluctuations observed | Lesser power requirement but more manageable output |
| Fuel requirement | Premixing of oil and gasoline; more consumption | No fuel premixing, less consumption; higher fuel efficiency |
| Emissions | Emit more smoke due to incomplete combustion | Cleaner exhaust emissions |
| Weight | Lightweight; estimated 227 lbs for 250 cc bike | Heavy in weight with more parts; estimated 240 lbs for 250 cc bike |
| Cost | Lower costs; estimated $50-$500 rebuilding cost | More expensive; estimated at least $1100 rebuilding cost |
| Handling | Less stable at the track | Better to handle at increased speeds |
| Suitable terrain | For technical terrains | For rougher terrains |
| Moving parts | Few moving parts | More moving parts which brings more weight |
| Maintenance | Easier to maintain | More engine parts so it requires more cost on maintenance |
Table of Contents
Dirt Bike Strokes: What Are They?
When we say dirt bike strokes, we refer to the piston motion inside the engine cylinder. The number indicated in strokes is the number of movements needed to complete an engine power cycle.
That being said, 2-stroke dirt bikes have 2 different piston motions. On the other hand, since 4-stroke dirt bikes require 4 movements, this also means longer completion of an engine cycle.
In the succeeding sections, we will elaborate further the similarities, differences, and distinctions of 4 stroke vs 2 stroke dirt bike.
Similarities
If you are to compare a 2 stroke vs 4 stroke motorcycle, here are some of their similarities to note:
- Internal combustion engines: Both 2-stroke and 4-stroke engines require an air-fuel mixture to facilitate combustion and pushing a piston down. The up-down motion is translated into rotational motion via connecting rod and crankshaft.
- Combustion cycle steps: 2-stroke and 4-stroke dirt bikes both have engines that undergo four steps of engine cycle–(1) intake, (2) compression, (3) combustion, (4) exhaust.
Differences
The following features will highlight the differences between 2 stroke vs 4 stroke motorcycles:
- Engine size: Smaller engines are observed on 2-stroke engines. This is expected since 2-strokes engines will complete spark plugs fires and internal combustion in two strokes. More strokes will require more space in an engine.
- Design: 2-stroke engines have simpler designs compared to the 4-stroke ones. Unlike 4-stroke engines, 2-stroke bikes do not have timing chain, valves, and camshafts.
- Power requirement: If we talk about 250 2 stroke vs 250 4 stroke in terms of power, the former creates more even when of the same size. The lesser the stroke requirement to complete a power cycle, the more power it produces.
Despite the huge power output, consistency wise, the 4-stroke engine bears more the said aspect compared to the 2-stroke engine as fluctuations are observed.
- Fuel requirement: 2-stroke dirt bikes require premixing oil and gasoline as its fuel since it gives lubrication to its internal parts to avoid wear after constant repetition of cycles. This is not a requirement for a 4-stroke engine for dirt bikes.
Efficiency wise, 4-stroke engines will also have higher fuel efficiency since gasoline is the only fuel of the burning process.
- Emissions: Since premixing of oil and gasoline is required in a 2-stroke engine, this leads to incomplete combustion which could contribute to more smoke generated.On the other hand, cleaner exhaust emissions will be observed for 4-stroke dirt bikes as long as gasoline is burned efficiently in the process.
- Weight: With smaller parts, it is expected that a 2-stroke engine is This can contribute to faster acceleration and ease of slowing down.
Meanwhile, a heavy 4-stroke bike engine might be useful when you are participating in a race where you consider the bike’s base weight.
- Handling: Due to its lighter weight, a 2-stroke dirt bike may be less easy to handle at increased speeds compared to a 4-stroke dirt bike. More frequent vibrations felt could affect the rider’s way of handling the bike.
In addition, a 2-stroke bike requires more shifting compared to a 4-stroke bike to stabilize the system as it navigates the challenging trails. - Suitable terrain: As dirt bikes produce a distinct sound that could be of disturbance to neighborhoods, your terrain must be fit for either woods riding or for trail riding.For 2-stroke bikes, it needs a terrain that would not involve too many obstacles as this may likely be thrown off course if there are several square edges, holes, or whoops.
- Maintenance: Fewer parts mean less to maintain which is the case for a 2 stroke engine on the dirt bike. This also means that for a 4-stroke engine that has more parts, it needs more cost to undergo maintenance operations.
Pros and Cons
Having presented the differences between 2 stroke vs 4 stroke dirt bike engine, we now summarize each pro and con on the said dirt bike engine types:
- Smaller engine size
- Lightweight
- Easier cleaning and maintenance
- More emissions
- Less efficient fuel burning
- Handling difficulties on rough trails
- Parts are more subject to wear
- Less shifting; better handling
- Less “jumpy”, easier to ride
- Reliability in delivering a stable power output
- Cleaner emissions with efficient fuel burning
- No pre-mixing of fuel required
- Heavy
- More expensive maintenance with more parts
Cost
It is expected that due to the number of moving parts a 4-stroke engine has, the costs would be greater vs 2-stroke engine.
If it was dirt bike rebuilding, the estimated cost for a 2-stroke bike is around $50-$500. On the other hand, rebuilding cost for a 4-stroke bike is more expensive due to more parts and may take around $1100.
Which is Easier to Ride?
As mentioned above, when increasing the speeds, the 4-stroke bike will be a tad easier to control despite it being heavier than the 2-stroke engine. Still, if you are a beginner, you can handle both dirt bikes if you choose an engine with a cylinder of volume as low as 125 cc.
Which is Faster?
Due to its being lighter, the 2-stroke engine can go faster than the 2-stroke one. However, the 4-stroke will help maintain the high speed longer.
Why is 2-stroke Engine Banned?
Over the years, there has been a shift with the usage of 2-stroke bikes to 4-stroke bikes due to environmental implications that could be detrimental. Listed are the following reasons for such initiative or even develop a better 2-stroke engine model:
- Release of emissions: Due to incomplete burning of mixed fuel, more smoke is released in the process. Gradual exposure could cause respiratory problems as it mixes with dirt.
- Higher non-renewable fuel consumption: Since the fuel used is a mix of oil and gasoline, these forms are considered non-renewable. Fuel efficiency is also lower vs 4 stroke engines.
- Greenhouse gas contribution: Smoke released is a mixture of vapors which already includes greenhouse gases such as carbon dioxide (a byproduct of fuel combustion) that contribute to global warming.
FAQs
What does 2-stroke mean on a dirt bike?
A 2-stroke on a dirt bike means that the engine undergoes 2 piston motions to power up and complete an engine cycle.
Are two strokes faster than 4 strokes?
Depending on which factor to consider, we need to assess how these contribute to the overall speed of a dirt bike. Both are actually designed to operate at fast speeds.
For instance, weight is a factor to speed as 2-stroke bikes are lightweight and 4-stroke bikes are heavy. This means initial power is relatively higher on 2-stroke bikes.
However, the consistency of a 4-stroke bike’s power without shifting too much can prolong its fast speed. Hence, a 150 cc 2-stroke bike is equivalent to the power that a 250 cc 4-stroke bike has.
Conclusion
The main distinction of a 2-stroke with a 4-stroke on dirt bikes is the kind of engine it bears and the number of piston movements needed to complete an engine power cycle. Both undergo the same steps but 2-strokes combine 2 steps in one stroke.
Now that we have compared the 2 stroke vs 4 stroke dirt bike, it is now up to you to select a bike for your adventures. After all, it will boil down to your skills and your ability to discern which one works best for you.
