Motorcycle Intake Systems – Which is Better, Fuel Injection or Carburetor? What are the Differences?

Motorcycle Intake Systems – Which is Better, Fuel Injection or Carburetor? What are the Differences?

I write about FCR carburetors all year round. This time, I'll add a bit of variety. I'll discuss the differences between fuel injection and carburetors from the perspective of a biker who loves FCR carburetors. While I can't delve into detailed technical specifics, I aim to make this understandable for beginners and intermediate riders. Use this as a topic for tomorrow's touring conversation.

To get straight to the point: fuel injection is simply outstanding. While considering the conditions of use and weighing the pros and cons, there are some good aspects of carburetors. However, overall, fuel injection is superior. Both systems operate differently, but they share the common goal of delivering fuel to the engine. They both supply the engine with a mixture of fuel and air.

So, let's get started!

How Fuel Injection Works

Most riders probably have a perception of fuel injection that goes something like this:
 "It controls the amount of fuel delivered via a computer." 
Let's delve into the details.

The ECU (Engine Control Unit) controls the ignition and intake. One of the components managing the intake is the fuel injection device. Fuel injection sends fuel to the engine under pressure. Imagine turning on a faucet and water coming out—that’s similar to how fuel is sprayed from the fuel injection system.

In contrast, a carburetor uses the negative pressure created when the piston moves down to draw fuel into the engine. The key difference in mechanisms is:

・Fuel injection pushes fuel to the engine.
・A carburetor allows the engine to suck in fuel.

This means that a carburetor operates primarily by the engine drawing in fuel. (Strictly speaking, some motorcycles also control ignition using a Throttle Position Sensor, or TPS.)

The ECU controls ignition timing and fuel delivery in response to external inputs such as throttle position, air-fuel ratio, pressure, RPM, gear position, and temperature.

Even with this brief explanation, it's clear that fuel injection is superior.

Weaknesses of Fuel Injection

Because fuel injection systems control the motorcycle electronically, they are vulnerable to battery issues. When something breaks, it affects all vehicles in the same way. It might be an exaggeration to call it a "weakness." The main thing to pay attention to with fuel injection is the battery.

Bump starting is not possible with fuel injection systems.

Fuel-injected motorcycles typically cannot be bump-started. While it might be possible, I would not recommend attempting it forcefully. Bump-starting is a feature that is more easily performed with carbureted motorcycles, especially when dealing with a dead battery. However, if there are issues with the regulator or generator, bump-starting might cause the engine to stall immediately or even lead to secondary problems such as harness fires. I do not recommend forcefully riding a motorcycle that is not in good condition.

What are the Advantages of Carburetors?

When writing about fuel injection, it’s hard to find many advantages of carburetors. They cannot adapt to changes in temperature or altitude. Fuel injection systems can handle many things that carburetors cannot. One advantage of carburetors is that they allow for bump starting. While both systems manage the intake, their mechanisms are fundamentally different.

The ease of repairing a carburetor compared to a fuel injection system depends on one’s perspective.

Carburetors are generally easier to access for disassembly, cleaning, and replacing spare parts. Most repairs for carburetors involve cleaning and replacing deteriorated O-rings or gaskets. However, this is only true for those with maintenance knowledge and spare parts on hand. For those without these resources, there is little difference between the two; both are essentially black boxes. Carburetors are more prone to causing trouble.

Overflow is not an issue with fuel injection systems.

Overflow is a problem unique to carburetors. Fuel injection systems, by their nature, do not experience overflow. Overflow refers to the symptom where gasoline spills out from the part of the carburetor that stores fuel. The fact that there is no overflow makes fuel-injected motorcycles more convenient compared to those with carburetors.

Fuel Injection Tuning

The difference lies in whether or not you have tuning equipment. Ultimately, if you have a complete set of tuning tools, there isn't a significant difference between carburetors and fuel injection systems. Fuel injection tuning is done via a tablet, with minimal physical work on the motorcycle. In contrast, tuning a carburetor requires disassembly. When comparing the time required for these tasks, fuel injection offers far superior convenience.

Motorcycle Intake Systems – Which is Better, Fuel Injection or Carburetor? What are the Differences?【summary】

Fuel injection and carburetors should be considered as completely different ways to enjoy motorcycling. Carburetors are entirely analog devices, offering a hands-on experience that many find appealing. I started tuning FCR carburetors on a whim. If the CBX1000 had been a fuel-injected motorcycle, I would have likely started tuning fuel injection instead.

Even if not working with carburetors, there are plenty of other areas of a motorcycle to explore and enjoy, such as the suspension, front forks, and brakes. These aspects contribute to the overall appeal of motorcycling beyond just riding.

Occasionally, I receive questions via email. I’ve also learned a lot from predecessors and have been helped by the information shared by anonymous individuals on the web. If you have any issues, I will do my best to provide answers within my knowledge. If you're interested in DIY projects, I encourage you to give it a try.

See you again!

CBX1000 – Photo Gallery

Here is a photo of the CBX1000 from a previous post, where the FCR stands out.