Next to the differences between 2-stroke and 4-stroke, the fuel supply is the next big thing about bikes with internal combustion engines.
Regardless of its size or shape, your motorcycle or scooter needs some way to mix the fuel and air for proper combustion.
This can be done with either a carburetor or a fuel injection system
In this blog post, you’ll discover:
- How a carburetor works, and the 5 parts of a CV carburetor
- Whether it’s spelled “carburettor” or “carburetor”
- Differences between fuel injection vs. carburetor
- Which was the first motorcycle built with fuel-injection
- How your bike’s name can tell if it has fuel injection
Prefer to get this information in podcast form? Listen to the 30 Minute Motorcycling Podcast episode about the differences between fuel injection and carburetors (and how the petcock works):
- What is a Carburetor?
- What is Fuel Injection?
- Quick Tip – How You Can Tell If Your Motorcycle or Scooter Has Fuel Injection
- Fuel Injection vs. Carburetor – In Summary
What is a Carburetor and How Does It Work?
The carburetor works by carbureting the fuel and air mixture (hence the name)
There are two main types of carburetors:
- Slide carburetor
- CV (constant velocity carburetor)
Since the CV carburetor is the most common one, we’ll focus on it for this blog post.
Parts of a CV carburetor:
- Float bowl – where the carburetor stores the fuel
- Throat – a narrow tube where air passes through
- Venturi – a narrow passage where the fuel is compressed as it flows through it
- Pilot jet – handles the mixture from idle to about 15-20% throttle.
- Needle jet – where the fuel passes through when the amount of throttle is 20-80%
- Main jet – controls the fuel mixture when your throttle is wide-open
- Choke – used to temporarily enrich the mixture during cold starts
- Petcock – controls the fuel flow
Is it “Carburetor” or “Carburettor?”
The main difference is that “Carburetor” is used in American English, while “Carburettor” is used in Australian and British English.
Instead, power is delivered through a metal cable that tensions as you squeeze the brake lever - similar to how many motorcycle clutches work.
Although not so much on modern motorcycles, these brakes are highly common on bicycles and e-bikes.
What is Fuel Injection?
First of all, fuel efficiency is much better compared to a bike with a carburetor.
Secondly, carburetors are much more sensitive to cold temperatures –
It’s for this reason that fuel-injected engines don’t need chokes – they’re much better at dealing with cold starts.
Which was the first motorcycle with fuel inejction?
How does fuel injection work?
When they detect a change in either the throttle position or the engine speed, the sensors send a signal to the bike’s electronic control unit (or “ECU”).
The ECU then uses the information from this signal to calculate when the fuel injectors should open and how much fuel the engine needs.
Quick Tip – How You Can Tell If Your Motorcycle or Scooter Has Fuel Injection
Then the ”i” at the end signifies that it has fuel injection.
It’s not always this clearcut, but if you see this “i” in the name of a motorcycle or scooter, now you’ll know what it means.
Fuel Injection vs. Carburetor – In Summary
- First introduced in 1980 for the Kawasaki Z100-H1
- Standard on most modern motorcycles and scooter
- It relies on electronics to control the fuel and air mixture
- If your bike has an “i” at the end of its name (e.g. “Kymco Like 200i”), it’s a sign that it has fuel injection
- More common on bikes in the past, although still around to a lesser extent
- Works by
- More sensitive to cold temperatures
- It comes in two forms – slide and CV
- In American English, it’s spelled as “carburetor” – in British English, it’s spelled as “Carburettor”