A motorcycle carburetor creates a mixture of fuel and air that makes the motorcycle move forward. The carburetor working principle is quite simple to understand, and we will explain to you the best way possible how it operates.
So how does a motorcycle carburetor work? A motorcycle carburetor is a device that mixes fuel and air in the proper ratio inside an engine with internal combustion. The carburetor controls airflow through the main bore. The air then draws the fuel and creates the mixture that enters the engine through the intake valve.
Stay with us as we will tell you all about the carburetor advantages, challenges, and other things that you may find interesting and useful.
Table of Contents
How Does a Carburetor Work?
In this section, we will cover the carburetor’s basics, such as what it does and its operating system:
- The carburetors main purpose is to deliver the proper fuel-air mixture to the engine with an internal combustion system
- The main bore or Venturi regulates the airflow
- The Venturi Effect is vital for the carburetor to operate successfully
What Does a Carburetor Consist of?
These are the parts of a motorcycle carburetor:
- center bore
- jets
- vents
- a bowl
- passages
- a slide
- enricher (Choke)
- idle speed adjustment
- fuel-air ratio adjustment
- accelerator pump
Motorcycle Carburetor Advantages
A carburetor has a few of its advantages, and these are:
- It is easy to repair, sometimes doesn’t require a skilled mechanic to fix the problem but can be done in your garage
- Most of the time, doesn’t need software or a computer for making adjustments
- It can operate without pressurized fuel lines
Motorcycle Carburetor Challenges
A carburetor also has some disadvantages or challenges, and we will mention them as well:
- It is less efficient in comparison to fuel injection, and this is most noticeable when you are decelerating or the engine is cold
- If you haven’t ridden a bike for a longer time, it can be a little bit finicky
- Motorcycles with multiple carburetors and multiple cylinders need to be synchronized, so they work properly; if they are not synced, they could experience difficulty in their function
These were the carburetor basics, and now we will let you know how a carburetor works more in-depth.
Interesting Fact: Many riders, including myself, thought that twisting the throttle controls how much fuel will flow into the engine, but surprisingly that is not quite the truth. The throttle regulates the amount of air sent through the carburetor, and the airflow regulates the amount of fuel sent into the engine.
The Venturi Principle/Effect tells us that when air travels through a narrowed part of a tube, airspeed accelerates while the air pressure lowers. When airdrop pressure happens, the fuel gets drawn out of the carburetor bowl, sent to several passages and jets, and last to the cylinder head.
Note: Click on this link if you want to know How to Fix a Motorcycle Carburetor.
What Is a Motorcycle Carburetor?
If you have never seen or heard about the carburetor, and this is your first interaction with it, you may think it is some complex part inside the motorcycle engine. But to be honest with you, it is not complex at all. The carburetor has one task to do: mixing the perfect fuel-air mixture. During the last decade, carburetors have been improved, upgraded, modernized, and updated, but the basic purpose of the carburetor, which is mixing air and fuel, has stayed the same.
What Makes Air Flow From the Carburetor into the Engine?
Negative air pressure is created when a piston gets down the cylinder bore of an engine with internal combustion. The negative air pressure, together with an open intake valve, gets air from the carburetor and takes it to the combustion chamber.
As soon as you twist the throttle on your motorcycle handlebar, a butterfly valve or slide lets air in, which takes a certain fuel amount out of the carburetor bowl. The fuel volume is regulated by a number of jets, passages, and vents, and it depends on what your engine needs the most.
Mechanical Slide vs. Constant Velocity Carburetors
Carburetors get in two categories:
- Mechanical slide
- Constant velocity
Mechanical Slide Carburetor
In this carburetor category, the throttle has a direct impact on raising or lowering the carburetor slide, which has control over the amount of air that flows through the bore and gets into the motorcycle engine.
Interesting Fact: Mechanical slide carburetors are used in off-road, racing, and similar kind of performance and are very popular in these sports.
Mechanical slide carburetors often have accelerator pumps built-in, which lets them maximum performance because this enables the fuel to be delivered at any moment.
Constant Velocity Carburetors
This carburetor category enables better operating through numerous altitudes, and the throttle has a better reaction in all throttle ranges. The handlebar-mounted throttle and the slide are not connected in constant velocity carburetors. A butterfly valve in the carburetor’s throat is opened by the throttle, allowing vacuum pressure to raise the slide as much as it needs to be raised.
Air/Fuel Ratio
The mixture ratio significantly impacts your engine’s lifespan, emissions, performance, and fuel economy.
A rider can adjust his diaphragm spring tension, jet sizes, and slide needle taper to achieve wanted performance outcomes. One of the ways to tune and dial an optimal fuel-air mixture ratio is to analyze the composition of the exhaust gas.
Although electronic fuel injection is more sophisticated than carburetors, carburetors can still present a challenge to some technicians.
Note: Air-fuel ratio (rich or lean mixture) can have an impact on cylinder head temperature.
Circuits
A carburetor has Three Main Circuits:
- Midrange
- Idle
- Main
Every circuit regulates the ratio of fuel-air mixture, which depends on what a rider prefers best. If the idle ratio is 14.7 air parts to 1 fuel part, previously mentioned three circuits will perform in such a way to enable that ratio all the time.
1. Midrage
This circuit is active when a rider uses partial throttle, which means that it is active when a rider accelerates from a stop position or during the rider’s gradual acceleration.
2. Idle Circuit
This circuit is active when the bike idles and the throttle is closed.
3. The Main Circuit
This circuit is active when a rider twists the throttle from 75% to fully open throttle (wide open throttle-WOT).
How Does a Carburetor Work on a 2 Stroke Engine?
2 stroke engine carburetors have the same task as the 4 stroke carburetor counterparts, and that is to make a proper fuel-air ratio mixture. However, they do it in a little bit different way.
2 stroke carburetors are capable of creating a pressurized, continuous loop of fuel with diaphragms and a primer bulb out of the fuel tank and into the engine with any fuel that has been left unused back in the fuel tank. There is no bowl that could temporarily store the fuel, but the system will be pressurized by mechanically priming the bulb, preparing the fuel system to be ready to send the fuel to the engine.
Here is a nice video that you can watch about motorcycle carburetor working principle:
Final Thoughts
At first, it may look to you that a motorcycle carburetor is a very complex part of your bike. Still, hopefully, we explained to you in detail how it works, carburetor types, and their characteristics. You should know the basics about the carburetor working principle and all necessary stuff related to the carburetor once you read this article.