Briggs And Stratton Blowing Gas Out Carb

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If you discover gas blowing out of your carburetor, you should try to fix it as quickly as possible to prevent you from inflicting additional damage to your engine and also for your own safety.

In this article, I explain the main reasons your Briggs and Stratton engine blows gas out of the carburetor and also provide simple troubleshooting tips to help you diagnose and also fix the problem.

Reasons Why Your Briggs And Stratton Blows Gas Out Of The Carburetor

The reasons your Briggs and Stratton might be blowing gas out of the carburetor include:

  • Stuck float needle valve
  • Dirty/damaged carburetor
  • Bad carburetor gasket
  • Damaged carburetor diaphragm
  • Carburetor adjustment screw set too rich

Tools You Need For This Job

  • Work gloves
  • Screwdriver
  • Clean rag
  • Compressed air 
  • Carburetor cleaner spray
  • Carburetor repair kit

Briggs and Stratton Blowing Gas Out Carb: Causes, Diagnosis, and Fixes

1. Stuck Float Needle Valve

A faulty float needle valve might cause your gas to blow out of your carburetor. It could simply be stuck, or it could have become so worn that it no longer functions properly. 

The amount of fuel that enters the carburetor is controlled by a float needle. The float needle may become gummed up and stuck in the open position due to residue from stale gasoline. 

As a result, fuel overflows the carburetor and gas begins to blow out of the carburetor.

The float may also become worn out over time. This float will stop the valve from closing as it begins to wear. This implies that the gas will continue to flow continuously. 

When this happens, the engine begins to flood, gas shoots out of the carburetor, and your air filter may even become soaked. 


  • Inspect the carburetor of the engine for signs of fuel flooding. Excess fuel indicates that the float needle is stuck.
  • Try moving the float needle slightly. If it does not move, it is stuck.
  • Check the oil compartment using the dipstick. If the oil appears too thin and smells like fuel, it is a sign that fuel has leaked into it as a result of the fuel float being stuck.


  • First, drain out the excess fuel from the carburetor
  • Use a carb cleaner to free the stuck float needle
  • Replace the float needle and needle seat with a new one if it is worn or damaged.

2. Dirty/Damaged Carburetor

Your carburetor may be dirty or damaged if gas is blowing out of it. Dirt may have clogged the carburetor jets or outlet causing an overflow of fuel in the carb.

It may also be damaged or cracked. This will cause gas to blow out of the cracked parts.


Check for clogged jets and cracks in the body of the carburetor.


Clean the carburetor with a carburetor cleaner spray if it is dirty. You can use a carburetor repair kit to fix any damaged internal parts.

Replace the carburetor with a new one if it is severely damaged or cracked.

3. Bad Carburetor Gasket

A carburetor gasket seals the carburetor to enable it to perform its function effectively. The carburetor gasket can get broken or develop a leak as a result of wear.

When the gasket breaks, it can no longer serve as a seal, allowing excess air to enter the carburetor. In some cases, fuel may also leak out through the crack in the gasket and blow out of the carburetor.


Check the carburetor gasket for cracks and leakage openings. If it is soaked in fuel, it is probably the cause of the problem.


Replace the carburetor gasket with a new one.

4. Damaged Carburettor Diaphragm

The carburetor’s diaphragm works together with the float needle. It aids in controlling the amount of fuel in the carburetor. 

It is constructed of a rubbery substance that can become stiff by repeated exposure to heat and fuel.

To perform its duties effectively, it must maintain flexibility. The diaphragm will flood the engine if it becomes too stiff or damaged and allow excess gas into the carburetor.

Your Briggs and Stratton carburetor may begin to blow out gas as a result of this.


Take out the carburetor and inspect the diaphragm. If it appears to be stiff or bent, it is damaged.


Replace the bad diaphragm with a new one. If the spring supporting the diaphragm is flat, replace it.

5. Carburettor Adjustment Screw Set Too Rich 

If your Briggs and Stratton blow out gas through the carburetor, the air-fuel mixture screw might be set too rich.

This means that it is set to allow excess fuel into the carburetor and combustion chamber. This will undoubtedly cause an overflow of fuel in the engine and excess fuel may begin to blow out of the carburetor as a result.


  • Drain out the excess fuel in the carburetor
  • Adjust the carburetor air-fuel mixture screw to prevent continuous overflowing of fuel.

How To Adjust The Carburetor Settings On A Briggs And Stratton Engine

  • Start the engine and let it warm up for about five minutes 
  • Remove the air filter housing and air filter 
  • Locate the adjustment screw on the side of the carburetor
  • Rotate the screw clockwise with a screwdriver until you feel a resistance
  • Turn the screw in the opposite direction for about 1½ turns to fine-tune it
  • Reassemble the air filter 
  • Start the engine and readjust if necessary

Is it Dangerous If Gas Is Blowing Out Of My Carburettor?

Yes, gas blowing out of the carburetor can be dangerous to both the engine and the user. 

Overflowing engines can cause engine damage. Fuel will begin to flow back into the intake if the engine overflows and it will have to run down the cylinder walls to do this. 

This is bad for a variety of reasons. The first is that it will contaminate your oil, preventing it from properly lubricating everything. 

Second, it will increase the wear on your piston rings. These are significant issues because they may lead to the replacement or rebuilding of your engine.

Also, it may result in fire outbreaks and harm the user. This is why you should try to fix the problem as soon as possible.


Gas may blow out of the carburetor of your Briggs and Stratton because of a stuck float needle valve, cracked carburetor, damaged diaphragm or carburetor gasket, or a wrongly adjusted fuel mixture screw.

It is important that you find the exact cause of the problem and fix it to prevent further engine damage. You can do this by following the troubleshooting guide in this article and applying the recommended fixes.