What Is The Difference Between Carburetors And Fuel Injection?

The ultimate goal is the same for these two fuel-delivery systems

I’ve often heard old-timers say they wish they could rip all the electronics off their new motorcycle, fit carburetors, and take control of their destiny. Well, I’m not sure carburetors are that simple.

Here is the venerable Mikuni VM carburetor. This is the float bowl. Fuel fills up the bowl—like the toilet tank filling up. The floats rise and press on the float valve. You bend the arms to change the float level.

If we want to make our bike pull well off the bottom, we might have to change the idle jet. Those jets have tiny numbers on them. If you are my age, bring a magnifier. To set the idle air mixture, you turn a screw.

To determine how the engine comes on throttle once it leaves the idle system, the front of the throttle slide—called the cutaway—may have to be higher, which is leaner, or lower, which is richer. I have boxes of different cutaways to tune the carburetor.

In the mid-throttle range, a tapered needle fits through a hole in the center of the slide and then through an orifice. As the slide lifts, the taper becomes smaller. There are many different combinations of tapers and diameters.

On top-end, throttle wide open, the main jet tells you whether or not your engine will sing that high, sweet song. If you want to tune with carburetors, you need all these boxes full of parts and you need to know how to play this particular organ.

On the other hand we can set this material aside and substitute electronic fuel injection. A fuel injector doesn’t have any tapers. It doesn’t have any little numbers on it. It is just a valve. It is either open or closed.

The computer on the engine tells the injector how long to stay open. When you want to change the fuel mixture on an injected racebike, a laptop is the tool. Plug in the cable, download the mixture curve, and, with a few keystrokes, relief is on the way.

Carburetors and fuel injection are just two different ways of accomplishing the same thing. Neither of them have a moral value. Anyone can learn the new way if he tries. I suspect I could learn it. You could learn it.