Briggs and Stratton Auto Choke Bypass(Choke No More)

Briggs and Stratton engines have been a staple in the world of small engines for decades. These engines power various outdoor equipment, from lawnmowers to generators.

One of the features commonly found in these engines is the auto-choke mechanism. This mechanism ensures a smooth starting by adjusting the air-fuel mixture during cold starts.

However, some users may prefer more control over their engines’ starting process.

This post delves into the concept of bypassing the auto choke in Briggs and Stratton engines to provide users with the know-how to make this modification.

Let’s dive in.

Understanding the Auto Choke Mechanism in Briggs and Stratton Engines

The auto choke mechanism in Briggs and Stratton engines is designed to regulate the engine’s air-fuel mixture during startup. When the engine is cold, it requires a richer mixture for combustion.

The auto choke restricts the air supply to create a fuel-rich mixture, aiding in easy starting.

As the engine warms up, the choke gradually opens, allowing more air to enter and transitioning to a leaner mixture suitable for continuous operation.

The Need for Choke Bypass

While the auto choke mechanism is effective in ensuring reliable starts, some users might have specific preferences or requirements that lead them to consider bypassing it.

Bypassing the auto choke gives users more control over the starting process, allowing them to manually adjust the choke and throttle to suit their engine’s needs.

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Benefits of Bypassing the Auto Choke in Briggs and Stratton Engines

Bypassing the auto choke can offer several advantages. Firstly, it allows users to customize the starting procedure, which can be especially useful for experienced engine operators.

Additionally, manual control over the choke can prevent over-choking, which may lead to excessive fuel consumption and carbon buildup in the engine over time.

Moreover, bypassing the auto choke can simplify the starting process in various weather conditions, ensuring a smoother and more predictable startup.

Tools and Materials You’ll Need

Before proceeding with the choke bypass, gather the following tools and materials:

  • Screwdrivers (flathead and Phillips)
  • Wrench set
  • Choke bypass kit (available at auto parts stores)
  • Safety gloves

Briggs and Stratton Auto Choke Bypass

1. Disabling the Auto Choke

Begin by disconnecting the spark plug wire to ensure safety. Then, locate the auto-choke mechanism on the carburetor.

Depending on the model, you may need to remove the air filter cover and housing to access it.

Use the screwdriver to carefully remove any screws holding the auto choke in place. Once removed, detach any connecting rods or springs.

2. Modifying the Carburetor

With the auto choke removed, you might need to make adjustments to the carburetor settings to compensate for the absence of the choke. Refer to your engine’s manual for guidance on adjusting the air-fuel mixture and idle speed.

3. Installing the Choke Bypass Kit

To simplify the process, consider using a choke bypass kit. These kits often include all the necessary components and instructions.

Install the kit according to the manufacturer’s guidelines. This typically involves attaching a bypass plate and adjusting linkages.

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Important Tips to Consider

  • Safety First: Always disconnect the spark plug wire before working on the engine to prevent accidental starts.
  • Manual Control: Understand the manual choke operation and practice using it before relying on it in critical situations.
  • Maintenance: Regularly inspect and clean the carburetor to prevent clogs and ensure optimal engine performance.

Potential Risks and Precautions

It’s important to note that modifying your engine’s choke system can void warranties or cause unintended performance issues.

if not done correctly. If you’re not confident in your mechanical abilities, consider seeking professional assistance.

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How the auto choke works on a Briggs and Stratton

The auto choke mechanism in Briggs and Stratton engines plays a crucial role in ensuring a smooth and reliable starting process.

When you start your engine, especially in colder weather, the auto choke mechanism comes into play to provide the optimal air-fuel mixture for combustion.

Here’s how it works:

  • Cold Start Detection: When you pull the starter cord or turn the ignition key, the engine control unit (ECU) detects that the engine is cold and needs a richer fuel mixture to start effectively.
  • Choke Plate Closure: In response to the cold start signal, the auto choke mechanism closes the choke plate. This restricts the airflow entering the carburetor, reducing the amount of air mixed with the fuel.
  • Rich Fuel Mixture: With the choke plate closed, the carburetor draws in less air, creating a fuel-rich mixture. This is essential for cold starts because a richer mixture ignites more easily at lower temperatures.
  • Enhanced Combustion: The richer mixture, along with the choke plate’s closure, results in a higher concentration of fuel in the combustion chamber. This makes it easier for the spark plug to ignite the mixture, even in cold conditions.
  • Gradual Choke Opening: As the engine starts and begins to warm up, the auto choke gradually opens the choke plate. This allows more air to flow into the carburetor, adjusting the air-fuel ratio to a leaner mixture suitable for continuous operation.
  • Smooth Transition: The transition from a rich mixture to a lean one is crucial for preventing the engine from stalling as it warms up. The auto choke ensures that this transition is gradual and seamless.
  • Optimal Performance: Once the engine reaches its normal operating temperature, the choke plate is fully open, and the engine operates on a lean air-fuel mixture, delivering optimal performance and fuel efficiency.

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Briggs and Stratton Auto Choke Problem

ProblemPossible CausesSolution
Engine Doesn’t Start1. Choke Plate Stuck Closed
2. Choke Plate Stuck Open
3. Faulty Ignition System
1. Check and free any obstructions around the choke plate.
2. Inspect the choke plate linkage and ensure proper movement.
3. Check spark plug, ignition coil, and wiring for issues.
Rough Idling1. Choke Plate Not Opening Gradually 2. Carburetor Blockage1. Clean or lubricate choke plate linkage for smooth opening. 2. Clean carburetor jets and passages.
Engine Stalls on Warm-up1. Choke Plate Not Opening
2. Incorrect Carburetor Adjustment
1. Check choke plate for proper movement; clean if necessary.
2. Adjust carburetor settings as per manufacturer’s guidelines.
Poor Fuel Efficiency1. Choke Plate Not Opening Fully
2. Incorrect Choke Operation
1. Inspect choke plate linkage; ensure complete opening.
2. Practice proper choke usage; avoid over-choking.
Black Exhaust Smoke1. Choke Plate Stuck Closed
2. Rich Air-Fuel Mixture
1. Investigate choke plate movement; address any issues.
2. Adjust carburetor for a leaner mixture.

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Is bypassing the auto choke reversible?

Yes, you can revert to the auto choke setup by reinstalling the original components.

Can bypassing the choke improve fuel efficiency?

Yes, manual control allows for more precise adjustments, potentially improving fuel efficiency.

Will bypassing the choke significantly change starting procedures?

It might take some getting used to, but with practice, starting the engine can become more intuitive.

Can I use the choke bypass kit on any Briggs and Stratton engine?

Kits are often designed for specific models, so ensure compatibility before purchasing.

Are there any legal restrictions on choke bypass?

While choke modifications are generally permissible, local emissions or safety regulations may apply. Check your local laws.

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Final Remarks

Bypassing the auto choke in Briggs and Stratton engines offers users the flexibility to customize their starting procedures.

This modification, though not without risks, can provide a smoother and more controlled startup experience.

By following the outlined steps and considering the precautions, users can confidently make this adjustment to suit their needs.

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George Bill
George Bill

George Bill is a Mechanical Engineer by Profession and an avid gardener and has been mowing his lawn for over 20 years. He has used a variety of different mowers during this time.
George is an expert at maintaining his mowers and over the years, he has learned many tricks and techniques for getting the best results from his mowers and is always happy to share his knowledge on this site.