Understanding the Choke on a Motorcycle: Function, Types, and Modern Alternatives

Motorcycles, especially those with carbureted engines, have a device known as a choke. This article explores the function of a choke, its various types, and how modern motorcycles with fuel injection technology have replaced this traditional component.

The Purpose of a Choke

A choke is a device that supplies a richer fuel/air mixture to the engine during the initial stages of starting, particularly during cold weather. This richer mixture helps the engine to start more easily and quickly. In most motorcycles, the choke is activated by pressing a lever on the handlebar, flipping a switch on the carburetor body, or pulling a switch on the dashboard of a car.

How a Choke Works

When the motorcycle is cold, the air in the carburetor is denser and contains less oxygen, making it harder for the engine to ignite the fuel. To compensate for this, the choke is used to provide a richer fuel/air mixture during starting. Once the engine warms up, the choke is restored to its closed position, allowing the engine to run on a leaner air/fuel mixture. This saves fuel and improves efficiency.

Types of Chokes

Directly on the Carburetor: Some older motorcycles have chokes that are mounted directly on the carburetor. This type of choke is activated by pressing a lever on the handlebar.

On the Engine Casing: In some cases, the choke is fitted to the engine casing.

Handlebars or Switch Casting: This type of choke is mounted on the handlebars or the switch casting, allowing the driver to easily access it.

Instrument Binnacle: Some motorcycles have chokes mounted on the instrument binnacle, providing an easy-to-reach location for the choke mechanism.

No Choke in Modern Motorcycles: It's important to note that not all motorcycles have chokes. In fuel-injected models, the ECU (Electronic Control Unit) automatically adjusts the fuel mixture for easy starting. Additionally, carburetor ticklers, which are similar but less complex, may be used in some cases to help with cold starts.

Modern Alternatives: Fuel Injection

Taking a step further, modern motorcycles often utilize fuel injection systems, which eliminate the need for chokes entirely. Fuel injection systems automatically adjust the fuel/air mixture based on the engine's temperature and other variables, allowing for smoother and more reliable starts even in cold conditions.

For instance, in a fuel-injected motorcycle, when the engine is cold, the ECU increases the fuel pressure and/or opens the throttle slightly to provide a richer mixture. As the engine warms up, the mixture becomes leaner automatically. This process happens seamlessly, often outside of the rider's conscious effort, making cold starts much easier and more efficient.

Conclusion

While chokes played a vital role in starting carbureted motorcycles, the advancements in motorcycle technology have rendered them largely obsolete. Modern fuel-injected motorcycles offer a more efficient and user-friendly starting experience. Understanding the functionality and types of chokes can provide valuable insights into the history of motorcycle engineering, while recognizing the evolution towards fuel injection demonstrates the ongoing innovation in this field.