Modern street bikes don’t come with a two-stroke engine. Most bikes are four strokers that offer higher torque and more fuel efficiency.
Still, there are many old-timers who miss the oomph of two-stroke engines.
So, this is a question mostly related to dirt bikes.
No matter the type of engine, performance is all about transforming heat energy into mechanical power. Quite simply, you can’t get more juice out of an engine without doing the right things.
Time to look into a few tricks that will help you to extract more performance from a two-stroke engine.
Does Two-stroke Engines Make More Power?
Honestly, when it comes to dealing with two-stroke engines, separating the facts from misinformation is an important task.
So, let’s focus on the straight answer to that question. Yes, it does.
Before I explain how two-stroke engines make more power, let’s take a quick look at the basics.
Firstly, a combustion cycle in an engine refers to the four stages of the fuel mixture intake, compression, combustion, and finally, exhaust.
The term stroke refers to a complete movement of the piston inside the engine chamber from top to bottom.
In a two-stroke engine, the entire cycle is completed in two strokes of the piston. That means it combines the intake and compression processes in one stroke and the combustion and exhaust in another.
And before you ask, four-stroke engines complete the same process in four piston strokes.
(If there were a harder way to explain that, you would find it)
Since combustion takes place at each stroke the power delivery is much higher than in four-stroke engines. Also, the power delivery is more linear.
So why are two-stroke engines not used in street motorcycles anymore?
The main reason is they consumed more fuel and oil and the pollution levels were much higher. They relied heavily on an oil-fuel mixture for lubrication. With unburnt oil particles, the exhaust fumes resulted in higher emissions.
How to Increase HP on a 2 Stroke Engine?
Before you go for any modification, make sure that the bike is in prime condition. Check the tires, suspension, filters, and carburetor to ensure that everything is in top condition.
One more thing: if your bike isn’t designed to handle racing fuel, using it won’t boost performance.
Here are a few tricks that will help in increasing the power delivery from a two-stroke engine.
(Without breaking the bank, I hope.)
Increasing Cylinder Volume
In theory, this is a simple and effective method. By increasing the engine diameter by a millimeter, you can increase the cylinder volume to hold more air-fuel mixture. The power and torque generated are directly proportional to the amount of fuel burnt.
Keep in mind, you’ll need to adjust the intake and exhaust ports to allow more fuel to come in and exit the cylinder
In addition, the slight decrease in weight will also help in improving the overall engine performance.
However, this isn’t something that you can do on your own. You’ll need an experienced technician familiar with the nuances of engine design.
The other option is buying a big bore kit to increase the cubic capacity of the engine. The right kit is used to replace the entire top end of the engine. While it’s not a cheap option, it can boost the power output by 10 to 15%.
Using a Velocity Stack
Velocity stacks have been around for decades and are no less popular. Basically, they are added to the airflow intake system. And the best part is, they are a cheap option for boosting power.
(Now you’re talking.)
The design of the stack allows more air to enter the engine and can improve the engine performance by 3 to 4%. In other words, it’s a force-feed mechanism that results in better airflow through the engine.
Velocity stacks are available in short and long lengths. Consult an expert to understand which design will work best for your bike.
Uncorking The Bike
This is a process where the airflow restrictions on the intake and the exhaust of the bike are removed. That allows the bike to breathe more freely and the engine to perform better.
(Reminds me of the ease of breathing without my face mask on.)
The purpose of these restrictions is to reduce engine noise and pollution levels. So, make sure that you’re not breaking any local laws by doing this. Also, removing the baffles from the muffler isn’t a part of the process.
For this, the airbox and exhaust are opened up to remove any restrictions. At the same time, you’ll need to recalibrate the air-fuel mixture entering the bike via the carburettor.
Otherwise, with all the extra air flowing into the engine, the bike will start running lean.
Adjusting or replacing the valves that control the gas flow through the carburettor is also termed jetting. This can be done even if you don’t uncork your bike. Obviously, you’ll need the help of a professional from the bike store to help you with this.
If you’re a pro, you can experiment a bit with the jet sizes to see how it affects performance. Aim for a richer mixture and then step down a size if you’re losing power.
Porting the Engine
Polishing the insides of the engine and the cylinder heads is another effective way to increase the power output by some amount. The small uneven spots or pits on the surface can affect the airflow.
Experts say that polishing makes the gas flow smoother and removes the turbulence in the flow path. With less resistance to the gas flow, combustion happens in a better manner.
Note, it needs special grinding and polishing tools, along with experience for getting the job done right. If you remove more material than necessary, the cylinder head will simply become unusable.
One warning though: while your engines may thank you for this treatment, your pockets may not.
Closer Look at Ignition
One important step to getting the best performance from a two-stroke engine is to keep the ignition system in top condition. That means you need to replace the spark plug periodically.
The process of precision fuel ignition through the mechanism of gap ionization is a complex one. Without the rightly timed spark, a lot of power is lost in the engine cylinder
We suggest that you select high-quality ignition wires and platinum tip spark plugs to ensure a high-energy ignition system that delivers the best power output.
While spark plugs have different designs, changing them as per your preference isn’t recommended. Always use the spark plug types recommended by the manufacturer to prevent any damage to the engine.
Frequently Asked Questions
How to get more power from a 2-stroke engine?
There are a few ways to get more power from a 2-stroke engine. Some of these methods include increasing the engine volume, increasing the airflow inside the engine, and polishing the insides of the engine.
How much more power does a 2-stroke make?
When engine speed is constant, the number of power strokes generated by a 2-stroke engine is double that of a 4-stroke engine. Overall, they produce more power per unit weight.
What are the disadvantages of a 2-stroke engine?
A major disadvantage is the overall efficiency of a 2-stroke engine is on the lower side. These engines also have a higher lubrication oil consumption rate which makes them highly polluting. The overall vibration levels and the noise levels produced by 2-stroke engines are also on the higher side.