Search
Close this search box.

2 Stroke vs 4 Stroke

Go karting uses both. The 2 stroke and the 4 stroke engines. The 2 and 4 stroke terminology are referring to the number of strokes the engine goes through. They each have their place in the go karting world. They also have their pros and cons. Recreational Application, and racing class structure will be the main determining factor. Below we try to dissect the 2-stroke vs 4 stroke argument.

Pistons moving up and down complete the cycles of a 2 stroke and 4 stroke engine.

Contents

Racing 2 Stroke vs 4 Stroke

There really isn’t a right or wrong answer about which engine is better to race 2 stroke or 4 stroke. There are some factors that may determine which engine class you race. The major factor is price. The current 4 cycle classes are much more affordable. For example, the LO206 engine is a sealed engine. Meaning that engine builders cannot disassemble and rebuild to produce more horsepower. This helps keep the cost down and allow new people to enter the sport without spending a lot of money.

You can purchase a complete ready to race LO206 engine for just under 1,000. On the other end of the spectrum some of the most popular classes for 2 strokes are IAME KA100, price $2,795.00. IAME X30 125cc TAG price tag is $3,295.00 and a Shifter Rok Engine comes in at $3,995.00. That is some big bucks to spend when first starting out.

The 2 stroke classes can be very expensive to start out. One of the most popular 2 stroke classes right now is the TAG engine. This is mainly due to the convenience of the Touch and Go features of the engine. The electric start makes this engine easy to start with one person. Some of the largest and most competitive races in North America are races with 2 stroke engines.

The 4-stroke engine is a fantastic way to get into the sport. Usually in a less competitive arena. Competition great to keep you pushing and learning. But too much competition when starting out can hurt your performance as well.

The 4 stroke engine also is a lower horsepower engine. Lower horsepower means all of the speed you have matters. Momentum is king. You will learn how to be smooth as a driver and that will pay off no matter which class you race.

Recreational 2 Stroke vs 4 Stroke

4 Stroke all the way. 2 stroke vs 4 stroke at home is an easy decision in my opinion. Especially when we are talking about kids. A 2 stroke engine produces a lot of noise and exhaust. Depending on where you live neither of those will be ok. A 4 stroke engine is quieter and produces much less exhaust.

A 2 stroke engine requires a mixture of fuel and oil. This mixture is not only the fuel but the lubricating oil for the rotating parts inside the engine. Additionally, this can create some reliability issues. If the fuel oil ratio is not correct internal wear or poor combustion can be the result. For these reasons alone I believe a 4 stroke engine is the best choice. 2 stroke vs 4 stroke, it doesn’t matter as long as you are having fun!

2 Stroke Vs 4 Stroke Cycles

4 Stroke

  1. Suck
  2. Squeeze
  3. Bang
  4. Blow

Yes, this is not the “proper” terminology, but it gets the point across. Like the title, 4 stroke implies” there are 4 strokes to the 4 stroke engine. The 4 strokes are completed in two full revolutions of the crankshaft. Whether there is one cylinder or 12 cylinders there are still 4 strokes. We will focus on a single cylinder 4 stroke engine as that is the most widely used 4 stroke engine today.

Intake “Suck”

The piston is moving from TDC to BDC. At the same time the intake valve is opening. The piston moving down in the cylinder creates a low pressure which draws in the air/fuel mixture.

Compression “Squeeze”

The piston has now stopped moving downward and will start to come from BDC to TDC. The intake valve has closed and no more air/fuel mixture is entering the cylinder. The mixture is trapped in the cylinder.

Combustion “Bang”

The piston is still moving upward to TDC compressing the gases. At a point determined by an ignition module or magneto, on the flywheel a high voltage pulse is sent to the spark plug. The spark plug is ignited and the mixture is set ablaze. This creates awesome power inside the cylinder pushing the piston back down to BDC.

Exhaust “Blow”

The piston is racing to BDC. At a point close to BDC the exhaust valve is opening. This allows the inert exhaust gases to escape. At this point some engines have valve overlap. This is a point where the intake valve starts to open when the exhaust valve is still open. This act called scavenging. This helps exhaust gases flow out of the cylinder. The most efficient engines pack as much oxygen as possible into the combustion chamber. Exhaust to an inert gas that will not burn again.

Round and Round

You may wonder? How does the engine keep rotating after there is no more energy left in the cylinder. The twisting or turning force (torque) of the engine keeps the cycles alive. The rotating members of a 4 stroke engine have mass creating torque. The heavy rotating parts want to keep spinning. When the piston starts to move back up on the intake stroke the rotating mass of the engine accomplishes that feat. The 4 strokes are completed thousands of times per minute.

2 Stroke

  1. Upward
  2. Downward

The 2 stroke engine is a simpler design with less moving parts. The cycle is completed in one revolution of the crankshaft and 2 strokes of the piston.

Upward “Intake and Compression”

The upward motion of the piston to TDC accomplishes two tasks. First the air/fuel mixture is pulled/pushed from the crankcase to the combustion chamber via the transfer channel. The transfer channel allows the crankcase air/fuel mixture to move from below the piston to above the piston for compression. When the gases are compressed and combustion takes place the Downward stroke begins

Downward “Combustion and Exhaust”

At peak compression the spark plug is ignited and combustion takes place thus starting the downward stroke. During the downward stroke the exhaust gases are pushed out by the piston moving downward. The area below the piston is connected to the area above the piston via the transfer tube. This causes the pressure below the piston to transfer to above the piston. The movement of these gases is referred to as scavenging. The exhaust gases are pushed out as the new air/fuel mixture enters.

The Motions

A 2-cycle engine is a lighter engine. The less moving parts reduce the overall weight. Improving the power to weight ratio. In a go kart racing application the rotating mass of a 2-stroke engine is lighter. Meaning that the engine can spin faster but less torque.

Why does a 2-Stroke engine Produce more Power than a 4-stroke engine?

Let’s use a 125cc engine. There is a 125cc 4-stroke and a 125cc 2 Stroke. If you put a 125cc 2-stroke and a 125cc 4-stroke on the track together at the same, the race would not even be close. The 2-stroke would destroy the 4-stroke.

Why is this?

Theoretically they are the same size. They are both 125cc engines.

Out of the two strokes in a 2-stroke engine the engine is producing power on one of the two strokes. So, 50 percent of the time.

Out of the four strokes in a 4-stroke engine power is produced one out of four. So, 25 percent of the time.

This means the 2-stroke is producing power on more strokes.

Why do we race with 4-stroke engines?

The 4-stroke engine is more efficient, durable, and produces less pollution. They are quieter and produce more torque due to the rotating mass.

Personal Note on 2 Stroke Vs 4 Stroke

I grew up racing in the WKA Gold Cup series. I started when I was 8 and we raced locally around Chestertown, MD and Belair MD. Each track ran 2 stroke and 4 stroke classes. We raced 4 stroke engines throughout my journey of karting. No doubt the 2 stroke classes were faster and higher horsepower class. Locally the 2 stroke engines were not as popular as the 4 stroke engines. For that reason, we raced in the 4 stroke classes.

Times have changed. The 2 stroke engine classes have gained a lot of traction. If you want to be the best, you got to beat the best. Right now, the best go kart racers are racing 2 stroke engine classes.

Return to BetterKarting to check out some awesome information about go karting!

Search the Best Racing Deals!

You DO NOT have to buy new! Find some of the best deals on used racing gear. Everything from go kart gear, trailers, parts and full go karts! Save money and buy used! 

RacingJunk Classifieds
RacingJunk Classifieds