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Overfilling a Motorcycle Gas Tank? (A Quick Guide)

If you are worried about your ability to fuel your motorcycle’s gas tank—don’t be. It is very easy and straightforward to do.

However, this does not mean that there are not some hazards that you need to be aware of. One such thing—and a question many beginners may have in my experience—is whether or not you can overfill your gas tank.

Overfilling a motorcycle fuel tank can occur when the gas pump auto shut-off does not engage or if you are manually filling up the tank. Overfilling a motorcycle’s gas tank can lead to gas leakage, engine stalling, and hard starting.

A zoomed in photo of a motorcycle gas tank.

Common factors that can lead to gas tank overfilling

Overfilling the gas tank of a motorcycle is easier than what one may expect. Overall there are several reasons why one can overfill their motorcycle gas tank, and below we will explore each one of them.

Poor Fueling Practices

When filling up your motorcycle’s gas tank, one of the things that you may have heard or read is that you should not stick the fuel pump’s nozzle all the way in—that you should leave the nozzle up and just a few inches in the tank.

The nozzle will be just barely inside the tank, and this will allow you to properly fill-up the gas tank and prevent the fuel pump from automatically shutting down too early.

However, one of the downsides to this is that you may quickly overfill your gas tank or create gas spillages and splashes.

Inaccurate Readings

Another reason why you may end up overfilling your gas tank is because of inaccurate fuel pumps. Although very rare, this is something that can happen to anyone.

Many motorcycle riders will keep an eye on the fuel pump’s reading and base their judgment when to stop on that, which could lead to them overfilling their gas tank.

This is why it is recommended to keep an eye on the fuel level in the tank.

Faulty Fuel Pumps

Fuel pumps are usually capable of shutting off when the fuel reaches the pump’s nozzle.

Once the gas reaches the little holes which are drilled at the tip of the nozzle, the fuel pump should automatically turn off, which should, in theory, prevent overfilling the gas tank.

However, this could cause a false sense of security as sometimes the auto shut-off may not work properly, and the gas could end up filling up the gas tank too much. (Faulty fuel pumps can overfill car’s gas tanks, too, so it is not something that happens only to motorcycles.)

Not all fuel pumps are created equal, and some may have a rubber (vapor) shroud that you may have to pull back not just to be able to see the fuel level in the tank but also to get the gas pouring.

These rubber vapor shrouds should be placed in such a way as to create a tight seal around the gas tank.

Still, doing that, people have found that the fuel pump will frequently fill about half the gas tank, and if the fuel pump were to not shut off automatically, they would not be able to act in a timely manner to prevent overfilling the tank.

Consequences of overfilling the gas tank

Spilling a little gas as you take the fuel pump out and away from the motorcycle’s fuel tank can happen to everybody, especially beginners.

This is normal, but there is one caveat. You should always clean any spilled gas off the motorcycle immediately.

Don’t leave spilled gas to dry on its own.

Overfilling your gas tank can also cause gas leakage out of the breather tube. This is not necessarily indicative of any internal damage as tank breathers are designed for that purpose.

Gas is caustic, and it will eat away and break down the finish and the paint, plastic, and any leather parts that it gets in touch with. If you are quick to clean the gas, you should be able to avoid any permanent damage.

What is more, gas fumes are also dangerous when inhaled.

When exposed to heat, gas will expand. This is why you should never leave your motorcycle out in the sun if you have overfilled your fuel tank, as this can also lead to fuel leaks.

Overfilling your motorcycle fuel tank can also cause hard starting and even stalling.

What is more, overfilling your motorcycle’s fuel tank is a fire hazard. If the fuel pump fails to auto shut-off, it will not only overfill the fuel tank but also spray it everywhere.

How full should the gas tank be?

The fuel level in your motorcycle’s gas tank should be one to two inches below the filler neck. Your motorcycle’s gas tank should not be more full than that as this may cause overfilling and fuel leakage.

How to avoid overfilling your motorcycle gas tank?

Fueling a motorcycle is very similar to fueling a car. However, there are some small—but very important—differences.

Follow the proper procedures for filling up the gas tank

  1. Pull up to the pump. 
  2. Shut off your motorcycle.
  3. Remove the fuel tank cap.
  4. Take the gas pump and put the nozzle just a little bit in the tank. You want to be able to see the inside of the tank. This way, you can monitor the fuel level. Make sure to get it just a little bit past the smaller hole to avoid any splashes.
  5. The general rule of thumb is that you never get a full tank by relying on the pump’s auto shut-off.
  6. Insert the fuel pump nozzle just enough to prevent any splashes back—about an inch or so past the filler neck.
  7. Squeeze the fuel pump’s trigger halfway, so it does not pour gas too fast. Don’t rush, keep the gas running slow and steady.
  8. Eventually, you will be able to see the gas coming up.
  9. Keep adding fuel until the gas reaches about 1 to 2 inches below the filler neck.

Know the capacity of the fuel tank

Know how much fuel your motorcycle’s tank can take. That way, you can make an educated guess on how much fuel you can fit in the tank by also paying attention to what the fuel pump says.

By knowing how much gas there is in the tank and how much fuel the tank holds in total, you can find how much fuel you can add before overfilling the gas tank.

Stay focused and monitor the fuel level

You know what they say; “Slow is smooth. Smooth is fast.”

Don’t get distracted; watch what you are doing. A lot of mistakes happen due to people getting distracted. And all it takes is a second.

You need to be able to see and listen to the fuel filling up the tank.

In fact, you don’t even need to get distracted to overfill your fuel tank. Some gas pumps are capable of pushing a lot of fuel in a very short amount of time. All it takes is a second, and you can end up with fuel splashing everywhere.

Don’t try to squeeze in as much gas as possible

One of the mistakes some motorcycle owners make is to try to fill up their motorcycle’s gas tanks up to the cap or slightly below it.

When subjected to heat, the fuel will expand, and this will cause messy fuel leaks.

Exercises extra caution when stopping at new gas stations

If you are at a new gas station and are not sure if the fuel pumps have auto shut-off, it is best to fill up the tank manually.

Don’t blindly trust the auto shut-off; you really don’t want to be unpleasantly surprised by a faulty gas pump.

What to do if you have overfilled your motorcycle gas tank?

If you have overfilled your gas tank or have just a little bit of spillage, you will have to clean up the gas.

Don’t worry. The motorcycle tank will not just explode, but it can happen, as it is a fire hazard, so exercising extra caution is advised.

Make sure to clean the splashes and leaks as soon as possible. Usually, near the fuel pumps, you should be able to find one of those paper towel dispensers that you can use to clean the gas.

Wash away the gas with some water, detail it and then wax any of the metal body parts that may have come in touch with the gas.

If you have overfilled your tank and you have already cleaned the gas, it is essential to let the area where the gas has leaked dry thoroughly. 

If you have overfilled your gas tank and the gas is above the filler ring, this will usually lead to gas leakage through the overflow tube. Do not panic. The overflow tube is designed to drain the gas. (However, it has not been designed for draining gas from an unattended fuel pump.)

Take the motorcycle for a short 10 to 15-mile ride to get the gas level down. This will prevent any gas leakages later due to fuel expansion.

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