2-stroke and 4-stroke kart engines are the most popular types you’ll come across, no matter if you’re racing or driving rentals. Whether you’re a beginner or a more experienced kart driver, it helps to understand where 2-stroke and 4-stroke kart engines vary.
2-stroke kart engines tend to be more prevalent in sprint karting due to their light weight and rapid acceleration, while 4-stroke engines feature prominently in endurance karting due to their fuel efficiency. 2-stroke go-kart engines offer better performance and are cheaper to maintain.
There are obviously far more differences and pros and cons to be weighed up with both of these engines. Below, I’ll go into those after explaining the basic science of a kart engine. I’ll also discuss a few of my favorite 2-stroke and 4-stroke karts!
How Do Kart Engines Work?
Kart engines work like regular combustion engines do, in that the piston is the primary thing that powers them. It moves up and down in a cycle. This cycle starts with air and fuel going into the combustion chamber, then the gases get compressed, then ignited, and then finally exhaust is let out.
Combustion engines all work in basically the same way, from go-karts to road cars. To get power and start moving, the piston within the engine’s cylinder needs to be going up and down. Specifically, the piston needs to hit two distinct points in the cylinder to properly allow airflow and therefore get combustion to happen for the go-kart or other vehicle to get going.
TDC & BDC
These two points are abbreviated to TDC (“top dead center”) and BDC (“bottom dead center”). As you can probably guess from what each means, TDC is the point nearest the top of the cylinder where the valves are located, and BDC is the position that is furthest away from these valves.
A stroke is when the piston moves from TDC to BDC, and vice versa, which is how engines are named. It’s based on how many of these strokes are needed to make a complete combustion cycle, which is broken down below:
- Intake: The piston first moves down the cylinder, which allows a mixture of fuel and air into the combustion chamber
- Compression: The piston moves back up the cylinder, and the intake valve is closed to compress the gases
- Combustion: A spark from the spark plug ignites these gases, pushing the piston down
- Exhaust: The piston goes back up the cylinder, and the exhaust valve is opened
Note: In a 4-stroke engine, each half-rotation – or stroke – of the crankshaft corresponds to one of these steps, while in a 2-stroke engine, each stroke performs two parts of the combustion cycle
How 2-Stroke Kart Engines Work
Typically, you’ll see 2-stroke engines on lawnmowers, weed-whackers, and even on toy planes, which all points to one thing: these engines are amazingly lightweight!
Although the size of the engine will differ, it’s the lack of extra components that keeps it very light when compared to other engines, and it also makes it fairly easy to repair if things go wrong.
This is because each stroke in a 2-stroke engine performs multiple parts of the combustion process. One stroke compresses the gas within the cylinder and ignites it, while sucking in fuel and air into the crankcase. The next stroke expels the waste gases at the same time as it sucks in more fuel and air for the next stroke. Who needs four strokes when two will do everything you need?
Due to the streamlined nature of this engine, you must mix your fuel and oil together to provide both combustion and lubrication.
How 4-Stroke Kart Engines Work
Whereas a 2-stroke engine has just two strokes doing all of the work, a 4-stroke engine requires – you guessed it – four strokes. This process requires two rotations of the crankshaft to complete the combustion process, which leads to the spark plugs firing once every other revolution, and power is generated every fourth stroke of the piston, following the 4-step combustion process we outlined earlier.
This type of engine is most commonly seen in larger devices that require propulsion and is even seen in normal road cars. Due to the higher complexity of this engine, you will find a separate compartment for oil to be deposited for parts of the machine to stay properly lubricated during this combustion process.
Are 2-Stroke Karts Faster Than 4-Strokes?
2-stroke kart engines are faster than 4-stroke kart engines. This is not only because of the power output of the engine but also because of the overall weight of the engine and the kart. 2-stroke karts will be faster than 4-stroke karts on straights, in acceleration, and through the corners, which means that they will be much faster over the course of an entire lap too.
2-stroke engines have the benefit of higher power output, which makes them faster overall. Generally speaking, a powerful 4-stroke engine such as the LO206 has around 9 horsepower. However, a 2-stroke Rotax engine can deliver 32 horsepower. Having triple the power output makes the engine perform much better, and it makes the kart faster in both acceleration and straight line speed.
2-stroke kart engines are also much lighter than 4-stroke engines. This is mainly because of their design. 2-stroke engines are much smaller with fewer parts and less complex building styles than 4-stroke engines, and this leads to a lighter kart overall. In other words, a 2-stroke engine has a much better power to weight ratio because of this, giving it an advantage in terms of straight line speed.
Because the 2-stroke engine is much lighter than a 4-stroke engine, it will also allow the kart to corner much faster. 2-stroke karts are much more nimble and agile in cornering, which gives them even more of an advantage over 4-stroke karts. Overall, a 2-stroke kart will be much faster than a 4-stroke kart over the course of a lap.
Key Differences Between 2-Stroke & 4-Stroke Engines
The 4-stroke engine wins in this regard because it only intakes fuel once every four strokes. Less fuel being consumed means that the engine can be powered for longer!
Because 4-stroke engines have more components, it goes without saying that they’re heavier than the simpler, smaller 2-stroke variant. Most, if not all, go-karts in younger age brackets have a 2-stroke engine installed, and this is because kids are lighter than adults. Lighter loads, plus a lightweight, smaller kart, wrapped up with a 2-stroke, makes for a winning package!
As with anything that has a great deal of pressure put on its parts, 2-stroke engines are more likely to wear faster and potentially break when compared to a 4-stroke engine.
For karts that spend more time on the track in longer races, a trusty 4-stroke will almost always be attached. The extra weight onboard doesn’t make such a huge impact when you want to run a long race because you won’t be hugely concerned about speed alone.
Although 4-stroke engines take more time to maintain and are generally more complicated to look after, they are generally more reliable. All of these factors make them a favorite for endurance racers. If you couple a 4-stroke with a clutch/gear system, although this adds more weight to the rig, you’ll also reach a higher top speed potential.
When comparing each engine in terms of their raw power output, the 2-stroke engine is the winner of the pair. It combusts far more frequently than the 4-stroke, and that means more frequent, responsive power!
More parts mean more to fix and, of course, they are more complicated to fix if things go wrong, which makes the 4-stroke the more complex of the pair. 2-stroke engines contain fewer parts and complex sets of extra valves, so they’re easy to perform regular maintenance on.
The fact that 2-strokes are very easy to maintain, with a lack of complicated parts to worry about, makes them very attractive to go-kart enthusiasts.
Because you aren’t mixing oil with fuel, the 4-stroke engine is considered to be more environmentally friendly than its 2-stroke counterpart, and it’s more fuel efficient. That, and the 4-stroke is also considerably quieter than the distinctive buzz-like roar of a 2-stroke engine.
How To Choose Between 2-Stroke & 4-Stroke Kart
It’s important to make the choice between a 2-stroke and a 4-stroke kart engine before you get into karting. Whichever engine you choose, you will likely need to stick with it because of the costs involved in buying and maintaining it. However, the decision is much simpler than you might expect. There are a few factors to consider when choosing your kart engine, but one of them is most important.
You need to choose the engine that your local championship is using. If you’re buying a kart to race in a series, you need to check what the engine requirements are. Most karting championships are ‘one make’ series, which means that there will be a specific engine that you need to use, such as Rotax for example. This will narrow your search down and take much of the decision making out of your hands.
But sometimes there will be multiple different championships that you could compete in. There might be a Vortex and a Rotax championship for example. In this case, you will need to make a choice between the different engines before you buy your kart. This makes it much more difficult as the decision will impact how your kart performs and which races you can enter.
If you just plan to use your kart as a hobby, the decision isn’t always as easy. In terms of the fun factor, using a 2-stroke engine is best. However, a 4-stroke engine will be the better option if you prioritize reliability and are on a budget. Use the table below to help finalize your decision.
2-Stroke vs 4-Stroke Kart Engines Compared
|2-Stroke Engine||4-Stroke Engine|
|Lighter weight||Longer lifespan|
|Higher performance||More durable|
|Better power to weight ratio||Less vibration|
|Cheaper to build and maintain||More fuel efficient|
|Less complicated maintenance||Doesn’t need fuel additives|
|Engine can operate in hot and cold temperatures||Quieter|
|More common in racing karts||Engine of choice for most rental karts|
The 3 Best 2-Stroke Kart Engines
1. Rotax 125cc
The Rotax 125cc kart engine is one of the most popular in the world. It’s used in multiple series worldwide, including official FIA events such as the Karting World Championships. It’s reasonably priced (in karting terms) with a range between $1,500 and $2,500 depending on the class of engine you’re buying. The engine is also affordable to run and easy to maintain, with excellent overall reliability.
Rotax engines are capable of producing speeds of up to 70 miles per hour (110 kilometers per hour), depending on several different factors, including the weight of the driver and kart, the gearing of the engine, and the track layout. This is the average performance of a 2-stroke engine, which is one reason that it’s such a popular karting engine.
The biggest benefit to choosing this engine is that you will always be able to find a championship to race in, even if you go abroad.
2. Vortex Rok
Vortex Rok engines are slightly more powerful than Rotax engines. However, they are also more expensive to buy and maintain. Vortex engines generally cost around $2,500 to $3,000. It’s important to keep in mind that your budget is critical in karting, and if you overspend you can’t head out onto the track. So, make sure you understand the costs before you buy one of these engines.
We mentioned that the Vortex is more powerful, which gives it the edge over the Rotax engine in tighter and twistier circuits. It can accelerate faster, but in general, they have similar top speeds. Again, it all comes down to the setup of the kart, the weight of the kart, and the track layout that you’re driving on. Rotax is known for excelling on fast and flowing circuits where the revs can remain high.
Another downside to using a Vortex engine is that the series is dying out (in the US especially). This is mainly due to the high costs involved with these engines. However, the junior series (Mini Rok) is still going strong for now. It might be worth investing in this engine if the championships are still going strong in your area, but just keep this in mind before making your purchase.
3. IAME X30
The X30 engine has become very popular in recent years. The X30 engine is also more expensive than a Rotax engine, but you can often find them at cheaper prices than the Vortex engine. Generally, these engines have a price range of between $2,000 and $2,500 depending on the class that you’re buying. Their maintenance and running costs aren’t too bad either, which is why they are often better than Vortex as well.
The X30 has a wider range in its power band, which also means that it can outperform a Rotax and Vortex engine. The average top speed for these engines is 75 miles per hour (120 kph), again depending on the factors mentioned above. The power band also means that the X30 performs better on tight and twisty tracks, which is the Rotax’s weakness.
However, the Rotax is better than the X30 on fast, flowing circuits. Nevertheless, the superior power to weight ratio of the X30 might still appeal to some drivers more than the Rotax engine. Just keep in mind that your overall costs will be significantly higher with an X30 engine than it would be with a Rotax engine.
The 3 Best 4-Stroke Kart Engines
1. Honda GX200
The Honda GX200 is one of the most popular 4-stroke kart engines, specifically for rental karting. This is because it’s quite affordable (especially compared to the 2-stroke engines I looked at above). The GX200 has a price range of between $600 and $800 depending on where you buy the engine from.
It’s not the most powerful kart engine out there, with a top speed of just 40 miles per hour (65 kph) depending on the setup of the kart and the track layout. It doesn’t have incredible acceleration, but that’s to be expected from a 4-stroke engine. However, the GX200 is a workhorse, and that’s why it’s such a popular engine for rental karting.
As a durable engine that can run all day, it’s perfect for hobbyists. Not only does it have a long lifespan, but the GX200 is also cheap and easy to maintain. It does have more parts than a 2-stroke engine, but it’s more robust and much stronger than a 2-stroke, which can make it cheaper in the long run.
The downside of the GX200 is the same as that you would get from any 4-stroke kart engine. It’s much heavier than 2-stroke engines, so there is a noticeable drop in performance both in straight line speed and through the corners. But overall, it’s a decent option if you’re looking to buy a 4-stroke go-kart.
The Briggs & Stratton LO206 kart engine is the go-to choice for many 4-stroke racing kart owners. Where the Honda engine was the more popular choice for rental karting, this is the engine you want to invest in if you have your own 4-stroke kart. This is the most popular 4-stroke engine used in championships worldwide. So, if you want to race, this is most likely going to be the engine you’re going for.
The GX200 and the LO206 are similar in price, with both costing between $600 and $800. They also have similar levels of performance, and you won’t notice much difference between the two over the course of a lap. However, the main difference between these two engines is that the LO206 is sealed, which is why it’s ideal for karting championships and professional races compared to the Honda.
However, the fact that the engine is sealed also means that you can’t make any performance adjustments to the engine, just like the 2-stroke engines above. Nevertheless, this is still a good thing, because it also means that there is less maintenance and costs involved in running this engine compared to the GX200.
With the engine being sealed, it also means that there is a level playing field for all drivers in the championship. If your aim is to race with 4-stroke karts, then this might be the best option you could choose out of the three listed here.
Tillotson 4-stroke go-kart engines are completely different to the other two mentioned above. First of all, they are more expensive. Depending on the model that you’re going for, they can reach prices of up to $1,000. The main difference lies in the design of the engine. Tillotson engines have a hemispherical combustion chamber compared to the flat-top design of the GX200 and the LO206.
Thanks to a larger bore and stroke in Tillotson engines, they can also produce more horsepower than the other two engines. Some of the models have as much as 20 horsepower, compared to the 9 horsepower of the Honda GX200 and the LO206. That’s a significant difference in power, and it could mean a much more fun experience if you have the need for speed!
The only problem is that there are very few championships that would allow this engine to be used unless they are single-make Tillotson engines. If you’re not on a tight budget and you’re buying a kart just to have fun, this might be the perfect 4-stroke engine for you.
2-stroke and 4-stroke kart engines hold some key distinctions that set them apart from one another. Mechanically speaking, 2-stroke engines perform one full combustion cycle every 2 strokes (one rotation of the crankshaft), while the 4-stroke takes 2 full rotations of the crankshaft to complete the combustion cycle (i.e. 4 strokes).
2-stroke engines are more popular for racing karts thanks to their better performance. But the reliability of the 4-stroke makes it the engine of choice for rental karts and many hobbyists that put a strong focus on durability.
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