Why Is Gas Leaking From The Carburetor Bottom? – Dangerous Situation.

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

Yes, this gas leaking from the carburetor problem is a problem with these little Grom Clone bikes. The stock carburetor has some inherent issues(covered more later), 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 Gas 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.

How To Stop Fuel Leaking From The Carburetor?

SHUT OFF THE FUEL SUPPLY!

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 gas leaking from the carburetor with gas pouring 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: Why Is Gas Leaking From The Carburetor Bottom, It’s The 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.  

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 carburetor fuel bowl with only two screws. Which will make you wonder why is gas leaking from the carburetor bottom sooner?

Once one screw becomes loose, the fuel bowl seal will rapidly fail and soon you will find gas leaking from the carburetor bottom fuel bowl gasket area.

How To Stop Fuel Leaking From Carburetor Bowl.

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.

My Road-side Fix For Gas Leaking From The Carburetor.

If gas leaking from the carburetor bottom while on a ride, you might have some problems.

First, shut off the fuel supply valve to the carburetor, no need to make a bad situation worse.

With the stock Boom Vader motorcycle carburetor, the fuel supply valve is on the side of the carburetor.  Turn it off.

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. 

Righty-tighty-lefty-loosey.

Getting angles and leverage on the screw heads might be a problem, but the goal is to get those fuel bowl screws tight enough so the carburetor fuel bowl holds gas just to get you home. Don’t be surprised if it to continues to have gas leaking from the carburetor bottom seal areas.

The fuel leak might slow down enough when the bike’s engine is actually running. Check.

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 repair options:

Option 1: Fix the leaking carburetor you have. (I did this fix first).

Option 2: Upgrade to a better carburetor (I did this later, also: Boom Vader Carburetor Upgrade).

Option 1, Fixing The Gas Leaking From The Stock Carburetor.

1.- Remove The Leaking Stock Boom Vader Carburetor.

IMPORTANT! You are working around gasoline, very flammable and potentially dangerous. At a minimum, I drained the fuel from the carburetor and practiced safe shop habits. Consult a motorcycle professional before doing this work yourself.

INFO: Gasoline – Illinois Department of Public Health.
FAQ: Motorcycle Garage Safety Rules.

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.- Cut Slots On The Carburetor Fuel Bowl Screws.

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

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 Bowl Screws And Checked The Fuel Bowl Gasket.  

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 Fuel Bowl 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 Repair Work For Continued Leaking Gas.

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

Check for carburetor fuel bowl gasket 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 Boom Vader Motorcycle Carburetor.

One way to fix a defective part, in this case, gas leaking from the carburetor bottom, is to completely replace the whole thing. I did this, and it’s the better choice.

I went with a cheap Grom Clone carburetor kit( Boom Vader Carburetor Upgrade Kit ), and the installation was easy for me.

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?

Hope this helps answers, Why is gas leaking from the carburetor bottom, and gives suggestions on how to fix your leaking carburetor fuel bowl gasket.

Always looking to hearing how you addressed this common problem with Boom Vader motorcycles, including gas leaking from the carburetor bottom fuel bowl gasket, so please comment below.

Ride Safe, Ride Fun!

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Boom Vader Gen 2 Upgrades