How To Adjust Carburetor On Briggs and Stratton Riding Lawn Mower

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Briggs and Stratton is an engine manufacturing company, and these engines are mostly used in powered garden tools such as lawnmowers. These Briggs and Stratton engines are gasoline-powered. So it uses gasoline as a power source to propel the mower and turn the blades for cutting grass.

Briggs and Stratton gasoline engines are designed with a carburetor that controls the gas flow from the task to the engine. Over time the carburetor can be malfunctioned, and cause the mower to perform significantly less optimal. Proper knowledge about how to adjust carburetor on Briggs and Stratton riding lawn mower can help you to adjust the malfunction carburetor very easily.

Why Carburetor Need Adjustment?

The carburetor controls the gas flow, so if it does not work properly, the engine will not be fueled. Fuel is what powers the engine, and without fuel, the engine is unable to function. There are a number of other reasons, and some of these are-

  1. The primary intention behind adjusting the carburetor is to make sure the engine runs smoothly. A properly adjusted carburetor makes sure ideal engine speed when the engine is idle, making the engine helps to run smoothly.
  1. For ensuring proper air, and fuel mixture when the mower engine is idle, it is mandatory to have a properly adjusted carburetor.
  1. The carburetor, in a manner, controls the way a lawnmower will behave when it is in an idle position. So if the engine is behaving or running roughly, adjusting the carburetor will ensure the engine runs smoothly when at idle position.

The carburetor is not digital, so it cannot adjust itself. You have to adjust the carburetor manually to make it work perfectly.

Carburetor Adjustment Safety

The carburetor adjusting process is not so risky but no process is 100% safe. It is easy to notice the good sides of a process, but we often overlook the process’s risk. Mostly you’ll be working with the baseline, but in between in the process, you have to start the engine. So, for preventing any sort of accident, you should follow these safety tips-

  • If your mower is very old, then the first thing you have to ensure that there is no fuel leakage. If you find any fuel leakage, then seal the leak appropriately or cause a backfire on the manifold.
  • You’ll not be working near the engine fan, but still, you have to keep an eye and keep your finger away from the engine fan. If your fingers get near it, then the fingers can get seriously injured.
  • Before starting the procedure, make sure that no part of the engine is hot. Stop the engine, and wait for some time to make the engine cool. Hot engine parts can cause you to get second or third-degree burns. Also, make sure the carburetor also does not get near any hot engine part.

You are working around chemical and running engine parts. So use gloves and goggles to be safe from any type of hazard.

How To Adjust Carburetor On Briggs and Stratton Riding Lawn Mower Step-by-Step Process

The carburetor controls idle speed and high speed. Let’s learn to adjust all of these.

Tools you’ll need to complete the process-

Adjusting the carburetor does not include any heavy tools, and it is very easy to do as well.

  • Gloves and goggles– These two tools will ensure safety while you will adjust the carburetor.

Adjust Idle Speed Mixture

Step-1: Turn of the engine

Ensure the engine is not running and shut off the engine at least 5-10 minutes before starting the procedure. Allow the engine to cool, and it will be easy to work with the carburetor.

Step-2: Remove the air filter

On top of the mower engine, there is an air liter. Locate it and the air filter cartridge. The filter is attached to the engine using some nuts. Loosen those, and remove the air cartridge and filter from the engine.

Step-3: Clean the carburetor

After removing the air filter, if you may see dust inside the carburetor, you can use a carburetor cleaner or compressed air to clean that.

Step-4: Adjust idle screw

Locate the idle screw, and use a screwdriver to adjust it. Turn the screw clockwise using the screwdriver until the screw’s needle touches the seat. After that, turn the screw counterclockwise with the screwdriver 1 turn.

Step-5: Adjust the high-speed screw

Along with the idle screw, high-speed screws also need adjustment.  Use a screwdriver clockwise until the screw’s needle touches the base. Then, use the screwdriver counterclockwise, and turn the screw 1 turn.

Step-6: Replace the air filter

After adjusting the screws, place the filter and cartridge at the place, and tighten those nuts that you have loosen before to secure the cartridge and filter. No need to put the cover back now.

Step-7: Start the engine

Now, start the engine of your mower, and make sure it is running on half throttle. Allow the engine to run for 5 minutes to warm it up.

Step-8: Fine-tune idle speed

You may see the engine running roughly. To make it run slow, turn the idle screw clockwise. Note at what point the engine is running slow. After that, turn the idle screw counterclockwise, and it will start to normalize. Continue turning it until you find a spot where the engine runs slow again.

Place the screw in the middle of these two points to get the best control over the engine at the idle position. The best idle speed for an aluminum-block engine is 1750RPM, and an iron-cast block engine is 1200RPM.

Step-9: Fine-tune high-speed screw

Set the throttle to fast from half. Turn the high-speed screw to your right until the engine gets slow, and note the point. Repeat the process counterclockwise, and note the point where the engine runs slow. Now set the screw at the center of these two locations for getting the best result.

Step-10: Test the lawnmower

Now use the mower in various conditions, and see the engine is running smoothly or not. If not, then fine-tune the idle and high-speed screw, and you’ll surely get the desired result.

Frequently Asked Questions

What can cause a lawnmower engine to run roughly?

Sometimes a very little thing like airflow issues can cause the engine to run roughly. To get the engine to run smoothly again, adjusting the carburetor will do. Adjusting the carburetor will make the air and fuel flow properly, which will help to run the engine smoothly.

How Can I adjust the carburetor on a riding lawnmower?

For adjusting the air-fuel mixture, you have to adjust the idle and high-speed screws. Use a screwdriver to adjust these screws and set those at an ideal position. After that, the air-fuel mixture will work fit and fine.

Final Words

After knowing how to adjust carburetor on Briggs and Stratton riding lawn mower, it is very easy. Adjusting the carburetor does not kill a lot of time, and by spending a little time, you can quickly fix your engine carburetor.

Even after using the fix, if the engine still behaves roughly, you should see a professional. This solution should work in most cases. But if the mower is very old, you should take help from a professional to avoid all types of risks.

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