What Is The Difference Between Carburetors And Fuel Injection?

Carburetors and electronic fuel injection represent two different ways of accomplishing the same goal. If you want to tune a carburetor, you need boxes full of parts and to know how to use them. When you want to change the fuel mixture on an injected motorcycle, a laptop is the tool.

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.

[ko]

How fortunate are we to have this resource. Thank you Mr. Cameron and Cycle World.

[cryalowicki]

Just to pile onto the carburetor, you have to make those tuning changes x4 times. One for each carb on the bike.

[williamrusk]

I club raced a rd 350 in the mid 70's, I had tackle boxes full of needles, slides, jets, I've learned the new way out of necessity, it's easy and it works

[kim]

Thank you, Kevin. Now I understand the difference and, who wouldn't want fuel injection. I have rebuilt two car carbs and they can be troublesome if you are not careful or have a little experience. I think my next bike will be FI. You really did a good job with showing and telling. And that is what makes a superior teacher.

[MrBlueberrypie]

Glad to see no dislikes. Mr Cameron has a brilliant style, and much knowledge. Very modest yet educative delivery. Thanks

[benrockwood]

These videos are fantastic Kevin, thank you for making them!!! I hope many more are to come.

[glowiever]

I love the efi system. my bike now feels like a car, almost zero maintenance.

[dballantyne]

What a wry legend you are Kevin. Keep up the great exposition.

[zerosensai]

We've no idea how good we've got it. Both with modern tech and these videos.

[stevemackelprang]

I rode to the top of Pikes Peak this summer on a fuel injected bike, and it never missed a beat, climbing to 14, 115 feet above sea level.

[Ubeleili]

Thumbs up for that! Now I know that I will never want to touch a carburetor if I can avoid it!

[deanrhodenizer]

Kevin, Thanks for a great video, but I still want to comment on where (I think) we are heading. First, without dating myself too much - I think I am probably older than you. My first significant bike was a BSA 650 (A10 engine, 1958 Model with a single Amal carburetor) next came a 1980 Suzuki GS850 with four Mukini carburetors and most recently a 2005 Yamaha FJR1300 with EFI. So, I am no stranger to rebuilding, tuning and synchronizing carburetors. The FJR has about 40, 000 Km (I am in Canada) and I have not needed to touch the fuel system. The point I wanted to make is that you described how to manually create a fuel map for an engine with one or more carburetors. Next you turned to doing something quite similar to a bike with EFI. The thing you didn’t mention is that it is still being done manually in some sense as the decisions for the mapping are coming from a human being. I believe the next step is for the logical rules to make these mapping decisions be embedded right in the bike itself and not on an external laptop computer. This would reduce the amount of time needed to get a bike to perform at its best for any given set of circumstances This would allow the bike to adapt quickly to run in an optimal manner without the need for any human intervention. For example, a race bike that can adapt to changing ambient conditions (e.g. temperature and air pressure) during a race (or from setup day to race day) would have, IMO, a competitive advantage. I’ll stop short of calling this artificial intelligence. It’s just a robot that is responding as programmed.

[dukejivetalker]

Carbs are not simple but once you get a good understanding it's easy to set up a carb.

[blipco]

I have a new Kawi z900. It has the most perfect fueling for any FI bike I have ever owned. Dare I say smoother than my perfectly carbureted bike.

[spenner]

"I suspect I could learn it."

[upsidedowndog]

No needle, seats, and bowls to gum up with FI. Petcocks became a quaint annoyance from years past.

[angelocardoc]

Why are there no 'direct injected' fuel injected engines on motorcycles, like we see in the car industry.
Direct injection is superior to port injection.

[danpetro]

Unfortunately no easy ways to go from carb to fuel injection; oh well if you own a vintage just will have to learn