My Motorcycle Is Leaking Gas. Six Possible Reasons

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Gas leaks can be a problem on motorcycles. It’s somewhat common among older motorcycles, but can surprisingly happen to new motorcycles as well.

Motorcycle gas leaks are not only annoying but also dangerous. It is possible that your motorcycle has begun to leak gas.

My motorcycle is leaking gas. Gas can leak from a motorcycle anywhere in between the motorcycle gas tank to the carburetor or fuel injector usually because a hose isn’t on tight, a gasket is worn, or a nut isn’t tight enough. The fuel petcock, carburetor and holes in the tank are all common places that a motorcycle can leak gas.

It’s important to promptly take care of a motorcycle gas leak. Gas leaks can cause gas to leak, which can result in exposure to harmful fumes, gas on clothes, lost money, and more wear and tear to your motorcycle. I’ve owned more than a dozen motorcycles, and have learned the best ways of repairing any gas leaks.

Petcocks Fuel

The fuel petcock, also known as the fuel valve on a motorcycle, controls the flow of gas from the tank. You can control this valve with either a butterfly handle, or a ball valve.

The fuel petcock is where gas leaks are most common on motorcycles. You can let the petcock leak anytime, even when it is turned on for gas flow.

Leakage from the gas tank’s bottom is a common reason for petcocks. Petcocks can also leak from their internal mechanism. This is because the gas tank has very few gaskets or o-rings, which can become brittle. Gas can then leak from the petcock’s body. These types of leaks can occur regardless if the petcock is in the on, off, or reserve positions.

It is easy to diagnose. The leak could be caused by a petcock in your motorcycle.

If you suspect the gas leak is from the petcock but not sure if it’s the gasket or the petcock itself, try replacing the gasket that goes between the petcock and tank first since it’s an easy fix. Empty the gas tank completely and remove the petcock. Replace the small gasket connecting the petcock to the gas tank. The right part should be available at an auto shop or online for just a few dollars.

Some petcocks don’t have a gasket. Some have the petcock welded to the gas tanks. To ensure a tight, leak-free fit, use a fuel-resistant gasket manufacturer. You should empty the gas tank before using fuel-resistant gasketmaker. After it has cured, add gas to the tank.

If you notice the leak is coming from the bottom of the petcock, it’s likely that the hose clamp is not tight enough. This is an easy fix that requires only tightening the clamp around the petcock.

If you have tried the previous methods and neither worked, or you suspect a faulty internal petcock leak, you’ll simply need to get a new petcock. These are quite affordable. When replacing the entire part, make sure that the gas tank and petcock seals are sealed properly.


The carburetor of a motorcycle delivers the right air and fuel mix to make the engine combust.

The second most common place you’ll have a gas leak on your motorcycle is the carburetor. A carburetor can leak gas if its gasket is worn or brittle. The carburetor bowl holds the gas that is being sucked into it. With the gas sitting there, it’s easy for the gas to leak if the gasket isn’t doing it’s job.

These gaskets are very inexpensive and I often find them online for a fraction of the price. To replace the gaskets, remove the carburetor and disassemble the bike.

A drain plug is located at the bottom of the carburetor bowl. This drain plug can also leak gas. These plugs can sometimes become loose due to vibrations from the motorcycle. Make sure that drain plug is tight so fuel won’t leak out of it.

Carburetors may also leak from their fuel connections. The fuel connection could be the one connecting the fuel line and the carburetor. It is possible for the hose clamp to become loose, so ensure that it is secure.

If you have a 2, 3, or 4 cylinder bike, you’re carburetors are going to be connected (essentially each cylinder has it’s own carburetor). Sometimes there’s a fuel bar that goes between the carb banks. These fuel bars need to have an o ring on both ends. For example, between carbs 1 and 2 there’s going to be two o-rings, between 2 and 3 there’s going to be two more and so forth.

Fuel can leak from these carb banks if any of the o-rings is worn. You should look for a gas leak in the middle of the two carburetors on your motorcycle. If this happens, use a light to see the location. Take your entire carburetor apart and search for the broken o-ring between the carb banks you have identified.

If you’ve determined that all the o-rings between the carb banks have become worn, replace all of them.

A video series I created about motorcycle restoration from start to finish. It includes a 25-minute video detailing how to clean and rebuild carburetors. You will also find other components that are difficult to tackle, such as the body and electrical. I give dozens of tips and tricks that you won’t find anywhere else online. Click here for more information if you’re interested in viewing multiple videos that will help fix up your bike or if you’re interested in completely building your dream motorcycle!

Holes in The Gas Tank

We’d like to think that because of the material a motorcycle gas tank is made out of, the only thing they’d be susceptible to is dents. Your motorcycle’s gas leak could be caused by gas tanks that have holes.

Holes in the gas tank are usually caused by rust but can also form if there’s a lot of wear on it (such as if it was dropped hard or dragged across asphalt). Older motorcycles are more susceptible to gas tank leakage, and they can be especially vulnerable if you live in humid areas.

A gas leakage problem is most likely caused by a gas tank leak. It will happen regardless of whether the motorcycle is turned on. It is possible for the gas tank to leak from multiple places, making it appear random.

If you are unable to locate the exact location of the hole in your tank, lift the tank slightly off your motorcycle while it is still connected to the fuel lines. Dry everything underneath so when the leak forms, you’ll able to easily locate it.

If you do have a hole in your motorcycle gas tank, you’ll simply need to get a new one. You should not try to repair the hole by yourself using a filler, or welding it. It can explode if you try to weld it. It is best to take the item to a professional who can handle it.

Fuel Injector

For the past 10 years fuel injectors were a standard feature on motorcycles. They are reliable in delivering the correct fuel and air ratio to the engine to power the motorcycle. A gas leak from your motorcycle’s fuel injector is one of the most common reasons for a motorcycle to be leaking gas. However, it is still possible.

You will find a fuel rail within a fuel injector and fuel injectors that have o-rings. For the most part these parts are durable and usually don’t have any problems with leaks. However, if you’ve been taking these parts in and out several times or if you’ve been working on the fuel injector, a gas leak can be quite possible.

Examining the fuel injector can help you determine if it is the problem. You will find it on the backside of the engine. You should inspect it for any signs of leakage.

Fuel injectors are a lot more complicated than carburetors because it’s an electronic system. So if you suspect your fuel injector is the reason your motorcycle is leaking gas, you’ll either need to take it in to a mechanic or get a new fuel injector altogether.

Similar Questions

Why is my motorcycle so rich? If your motorcycle has 02 sensors, it is possible for the motorcycle to run dry. For more information, click here.

Why does my motorcycle keep crashing? Motorcycle backfires are caused by uncombusted gasoline in the exhaust pipe. This is due to incorrect timing, too many fuel, loose exhaust pipes, too short of fuel, too little fuel, intermittent spark, and too much fuel. For more information, click here.

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