Water in Motorcycle Gas Tank (Symptoms & How to Fix!)

Water in gas tank - thumbnail

Water can get into the motorcycle gas tank after a wash or rain.

If the gas tank cap is not tight or not right, water leaks into the tank.

To remove the water, you have to drain the gas from the fuel pipe. Use alcohol or water-removing additives to clean the tank. And only after then pour fresh gas.

So, let’s dive into the symptoms of water mixed in the gas tank, its negative effects if left unchecked, how to drain the water content, and preventive measures.

Symptoms of water in the gas tank

In general, water in the gas tank is tough to identify.

The symptoms are not at all obvious.

I mean, rough acceleration and idling can be due to several reasons. One of them being water in the gas tank.

Yet, I hardly would suspect water when faced with rough idling and acceleration.

Still, here are the symptoms of water in your motorcycle gas tank:

First symptom. Water accumulated on the sides of the gas tank cap.

Water droplets on motorcycle gas tank

When you open the gas tank by taking out the cap, if you notice water accumulated on the sides in the area the cap was, then most likely water has entered the gas tank.

This is applicable especially after a heavy rain or motorcycle wash.

Second symptom. Low power, poor acceleration, and rough idling.

Motorcycle rider with feet on ground

This is generic.

But when there is water in the gas tank, this is exactly what happens with the motorcycle.

Still, it’s tough to trace back the problem to water when the engine is underperforming. There may be 100 other things that can cause the engine to perform badly.

Third symptom. Motorcycle starting problems despite everything seeming alright.

When there is too much water content in the gas tank, starting problems are bound to happen.

A guy push starting a motorcycle

You can even see the engine malfunction light ON.

If all things are alright, then you can check the fuel for water.

Fourth symptom. Water droplets on the exhaust or too much smoke.

White smoke coming from a motorcycle exhaust

This is applicable only when there is too much water in the gas tank.

The water exiting the muffler will come out as steam (lots of smoke) or settle on the muffler interior as water droplets.

Last symptom. The fuel smells bad.

This is not universal.

Many don’t smell anything different from the fuel.

But I felt the gas tank smelled foul when water was mixed in my motorcycle gas tank.

Motorcycle gas tank cap opened

Maybe it’s a coincidence. Or maybe the water was in my gas tank for far too long.

Either way bad smell was what tipped me off. Made me check if the gas had gone bad or anything.

Not these starting problems or rough acceleration issues.

So look out for gas tank smelling.

How to get water out of the motorcycle gas tank – Solution

Here’s what you need to do:

First, if the motorcycle is a carbureted motorcycle, turn the reserve fuel switch OFF.

Reserve fuel switch

Then disconnect the fuel pipe from the petcock.

Now place a pipe to the petcock and the other end into a bottle or container to collect the gasoline.

Motorcycle fuel pipe

Next, turn the fuel petcock to the RES position.

This ensures the gasoline from the reserve fuel tank drains as well.

A guy turning the fuel petcock

Let the fuel drain completely from the gas tank.

This might take some time.

Make sure the gas is completely emptied out from the tank.

Draining gasoline from the gas tank

Once emptied, check the bottle/container for water.

Water is heavier than gasoline.

So given enough time, water will settle down at the bottom of the container and the gas floats above.

Bad gasoline

This will give you a clear indication of how much water was there in the gas tank.

Now that the gas

For fuel-injected bikes, you need to take out the fuel pump and then drain the fuel from the gas tank.

Another method is to take out the gas tank itself out of the motorcycle. And then drain the gas.

Motorcycle gas tank taken out

This is a cumbersome and time-consuming process. Avoid taking the gas tank out as much as possible.

Once you have drained the gas out of the tank, it’s time to remove any water droplets remaining out of the tank.

How do you do that?

By using rubbing alcohol or a water-removing fuel additive.

Water remover fuel additive

Pour alcohol or the additive into the gas tank now. If you are using an additive, mix it with a small amount of gasoline and then pour it.

Then drain the additive mixed gasoline again from the tank.

This ensures the water is removed completely from the motorcycle gas tank.

Lastly, check the fuel filter. If there was too much water in the gas tank (based on the collected gas in the container), replace the fuel filter as well.

Motorcycle fuel filter located below the gas tank

Once done, fit the fuel pipe back.

Pour fresh gasoline into the tank.

Pro tip:
You can also use the drained gasoline if you separate the water out.

How do you separate water from gasoline?

Keep the container upside down overnight. The water settles down at the bottom and gasoline floats above.

Separating gasoline and water

Remove the water portion and a bit of gasoline as well.

The remaining gasoline is good for use. You can pour it back into the gas tank.

Gasoline in plastic bottle pouring into gas tank

Once you have poured fresh gasoline into the gas tank, start the motorcycle and idle it for some time. You are forcing the old gas in the carburetor and the engine out.

Only then, shift the gear on and go for a ride.

What happens if water gets in the motorcycle gas tank?

Here is what happens if the water gets into your motorcycle gas tank:

  • Gas tank corrosion: Long exposure to water can make the motorcycle gas tank start rusting. Water
  • Engine seizure: Too much water in the gas tank can lead to water accumulating in the combustion chamber. Hydrolocking and engine seizure might be the worst consequences.
  • Low power and mileage: With water mixed in the gasoline, the engine won’t combust properly. Resulting in low fuel mileage and low engine power.

Preventive measures

Here are a few preventive measures to avoid water getting to the gas tank.

First and foremost, clean the holes below the gas tank cap.

Motorcycle Gas tank holes where water can flow

These holes are designed to allow water to flow through and not get into the gas tank.

So keeping the holes below the gas tank clean prevents water from entering the gas tank.

Second, check if the gas tank cap is damaged or broken or if the cover/gasket is leaking.

Gas tank cap

If yes, change the gasket or the entire cap.

This should fix the water mixing in the gas tank.

Third and last, drain the gas if you are leaving your motorcycle idle for a long time.

Motorcycle sitting idle outside

If the motorcycle sits idle for too long, say more than 3 months, the gas and water (even the smallest amount) start to separate out in the gas tank.

The water settles at the bottom of the gas tank. This can get difficult to drain out. Taking out the gas tank might be the only solution.

So empty out the gas if you are not going to ride your motorcycle for quite some time.

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