Why Is Gas Leaking From The Carburetor (Boom Vader Motorcycle)?

One of the common questions asked soon after getting your new Boom Vader motorcycle built and riding is why gas is leaking from the carburetor.

Yes, this is a common problem with the little Grom Clone bike. The stock carburetor has some inherent issues, and we can start from the most common gas leaking causes to the least likely reason for your stock carburetor to leak gas.

Note: I am not covering all reasons a motorcycle carburetor can leak gas, just the common reasons why a Boom Vader motorcycle can leak gas right out of the box or while still new.

So, What Causes Fuel To Leak From The Carburetor?

The carburetor is not functioning as it should. Well, that was an oversimplification of the problem. :p

Well, let me break this down to two things that can be wrong:

  1. Carburetor is getting too much fuel, and it’s overflowing gas.
  2. The carburetor isn’t holding the fuel properly.

Believe it or not, the most common problem with the Boom Vader is the fuel needs to be appropriately held inside the carburetor.  

So with the most common cause of fuel leakage identified, let’s focus on fixing this problem—a leaky fuel bowl seal.

Stock Boom Vader motorcycle carburetor gas leakage.
Gas leakage started early with my stock motorcycle carburetor.

How To Stop Fuel Leaking From The Carburetor?


I can’t believe I’m writing this, but the immediate solution to a leaking carburetor is to stop the gas supply to the carburetor.

I needed to point this out because I’ve seen people post videos of carburetor leaking gasoline all over the ground, and the person just stood there filming. What a waste.

So, now that you stopped the fuel supply to the carburetor, why is the carburetor leaking gas, and how do we quickly fix it?

Most Common Problem: Gas Is Leaking From The Carburetor Fuel Bowl Seal.

Between the fuel bowl and the carburetor body is a seal, and this seal relies heavily on being compressed between the two mating surfaces.  

It looks like an o-ring, but shaped not like an “O” but follows a grove that wraps around the interior of the fuel bowl.

Design issue with the stock Boom Vader carburetor, as mentioned, this seal relies on compression to seal, and the stock carburetor comes with two, yes only two, screws holding on the fuel bowl.  

Stock Boom Vader Carburetor fuel bowl screws, fuel shutoff visible.
One of the two screws that hold the carburetor fuel bowl in place.

So if only one screw loosens, the seal is broken, and you lose one, unlike the standard four or more fuel bowl screws. The others help maintain some time of seal or slow the leak down enough to prevent total seal failure.

Yes, back to the Boom Vader motorcycle carb with only two screws. Once one screw becomes loose, the fuel bowl seal will rapidly fail.

How To Fix A Leaking Carburetor Fuel Bowl Seal?

Let’s first cover how to try and fix the leak while on the road. Understand any fix on the street is temporary, and your bike should be looked over as soon as you get into a garage.

Road Fix For Leaking Carburetor Fuel Bowl Seal.

First, shut off the fuel supply valve. The stock Boom Vader motorcycle carburetor, it’s on the side of the carburetor.   

Second, understand that there are only two screws on the stock carburetor, and both have no slots. So using a screwdriver is out. If you have a fundamental motorcycle tool bag, there should be pliers, or needle-nose pliers, in your kit. Get a hold of the screw heads and tighten them down. 

Getting angles and leverage might be a problem, but the goal is to get those screws tight enough so the carburetor fuel bowl holds gas just to get you home.

Third, once you tighten the loose screw, it can loosen again while riding. So every few miles, stop and check if the carburetor fuel bowl is leaking again. Also, this is a chance to re-tighten any loose screws.

Garage Fix For Leaking Carburetor Fuel Bowl Seal.

Say you noticed the carburetor was leaking gas on the road, and you finally got home, or you even noticed before going out for a ride the carburetor fuel bowl was leaking gas around the seal. 

You have some options:

  1. Fix the carburetor you have. (I did this fix)
  2. Upgrade to a better carburetor (I did this, also: Boom Vader Carburetor Upgrade).

Let’s look at fixing/modding the stock Boom Vader carburetor.

1.- Remove the carburetor after draining the carb and taking all the safety precautions ( My Motorcycle Garage Safety Rules – FAQ ).

Caution: The fuel shut-off is built into the stock carburetor. So removing the carburetor fuel supply line creates a direct path to the motorcycle gas tank, with no valve. You can put in a valve or kink the hose, but if unsure, please get technical help.

2.- Create slots on the fuel bowl screws.

I used a hack saw, but others have used a Dremel and reciprocating saws.  

Stock Boom Vader motorcycle carburetor fuel bowl screw with new slot cut.
Slot cut into stock fuel bowl screws.

Whatever way you do it, be safe.  

Metal shavings can fly, and we don’t want those metal shavings in places it does not belong. Use safety glasses( Safety Glasses With Readers ) and clean around the carburetor before openings.

3.- Removed the screws and checked the condition of the seal.  

Is the fuel bowl seal cut? Is it missing? Depending on the situation, you might consider upgrading to a more user-friendly version of a motorcycle carburetor.

4.- Use some thread locker and reinstall the screws.

Remember, the rubber seal works by compression; once the metal seating services are in contact, the seal is compressed, and no need to crank down on the soft metal.

5.- Test Your Work.

Be prepared for a gas leak, and re-initiate fuel flow to the carburetor.  

Check for leaks.  

You might put a band-aid on a broken neck, but there are slots. If the fuel bowl starts leaking on the road, you can tighten the screws.

Option 2, Upgrade The Motorcycle Carburetor.

I did this, and it’s the better of choices. I went with a cheap Grom Clone carburetor kit( Boom Vader Carburetor Upgrade Kit ), and the installation was easy.  

Boom Vader 125cc Carburetor upgrade kit.
Boom Vader 125cc Carburetor upgrade kit.

I eliminated some known issues on the Boom Vader motorcycle, and having a carburetor I could tune opened up the motorcycle engine quite a bit. 

Read more about my Boom Vader Carburetor Upgrade.

What Did You Do To Fix The Carburetor Fuel Bowl Leak?

Always looking to hearing how you addressed this common problem with Boom Vaders, so please comment below.

Ride Safe, Ride Fun!

Click To See My Recommended

Boom Vader Gen 2 Upgrades

Picture of me, as a New Motorcyclist.
Just Me…Newly Licensed.

Hi I’m Tom, A New Motorcycle Rider and Blog Author.

I am a new rider(Pa Learners Permit at the end of 2020, and I received a Pa Motorcycle License in 2021 after passing a Motorcycle Safety Course).

I bought my first motorcycle, a TaoTao TBR7, at the beginning of 2021 and have been doing upgrades on that motorcycle since.

I added to my motorcycle collection by buying a Boom Vader Gen 2 in 2022, and that Grom-Clone motorcycle has been upgraded by me as well.

I continue to ride my Boom Vader Gen 2 motorcycle as well as my TaoTao TBR7 dual-sport bike.

Read more on my About Me page.

Fun Fact: I’ve only been on one group ride.

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