How to Clean Out a Motorcycle Gas Tank – Removing Rust and Dirt

How often do you ride your bike? If it’s not quite often and your bike sits for a long time, some of its parts and components might be dirty, rusted and wet.

The truth is that no user manual will tell you how to clean a motorcycle gas tank, which is one of the reasons why people usually fear doing this. However, it’s nothing to complicated and can be done with nothing but the minimal skill set and several tools.

A rusted and dirty fuel tank is a problem for several reasons, so continue reading to learn how to deal with this in the easiest way.

Is Cleaning Better Than Replacing?

You can always replace, but why not try to clean it a little before investing in a new one? Rust and dirt from within can contaminate your fuel (read more about how to carry extra fuel), which is definitely something you want to avoid.

If the tank is damaged, dirty and rusty beyond repair, you’d have to replace it anyway. However, if there are only mild corrosion and dirt, you can probably clean it. This is a good way to avoid added expenses of replacing the tank altogether.

So, cleaning isn’t necessarily better than replacing. It might be a bit easier and cheaper, but that depends on how dirty and rusty the tank actually is.

Assess the Situation

Before you do anything, you want to inspect the tank and what condition it’s in. It might be too rusty or constructed in a way that would make cleaning too tricky.

You want to know what to expect since only then you can clean it thoroughly. For this reason, it’s important you have a clear image of what the inside looks like.

Assess the rust level, the construction, and also how rare the model is. These three simple steps can make further process much easier in terms of gathering tools as well as cleaning.

Rust Level

You should inspect the tank to figure out the rust level you’re dealing with. If you have to remove the rust, you’ll have to choose between a few methods.

Still, before you start with any of them, you need to check if there is any visible damage. The best way to do this is with a flashlight. With a bore scope, you can inspect the inside for any damage and flaws.

A combination of rust abatement techniques is a good way of dealing with mild rusting. The entire process is relatively simple and doesn’t take too much time.

Construction

Some models are different than others and as such, require a different approach. Think about old Harley-Davidson models with high survival rates due to the thick steel they’re constructed with.

Nowadays, bikes have tanks made of lighter gauge metal. If you have a thin steel tank, you might find the rust within quite consuming. In these cases, it might be too difficult to clean it. It could be beyond saving, depending on how often you cleaned it before. 

Also, some tanks are constructed differently in terms of accessibility. Certain models are nearly impossible to reach within, which tends to make the cleaning process quite tricky.

Rarity of Model

Another thing you should consider is how rare the model of is. Some that are considered high-production tanks tend to be easier to deal with than those of lower production.

Think about the paint since you’ll probably damage it in some places. Original paint helps retain the initial value of your bike. Putting a bit more effort into the process is worth solely for retaining value. A tank that’s in its original state is always worth more than the one that’s obviously been tampered with.

rusty motorcycle gas tank

Determine Rust Abatement Methods

Manual

If you opt for manual abatement, you’ll need an abrasive material for removing those heavy rust deposits. Before you start, make sure to evaluate the damage so you can have a clear image of what you’re dealing with.

The first thing you can do is place several small bolts and nuts inside the tank. Place them inside and shake it around. This way, the small nuts and bolts with strip away the scale build-up.

You can also use some BBs and gravel for this, as well as pretty much anything that can move in the tank without getting stuck.

These pieces flying around your tank will remove the rust build-up to a certain extent. This method might not be the most effective if the rust level is high.

Chemical

Chemical abatement is usually used in restoration. It requires mild acid such as vinegar for example. Vinegar uses an etching action, eating and removing the rust from the inside of the tank.

Still, it has to be mild acid; otherwise, it could eat up and damage the tank itself, which is something you want to avoid. Products like a motorcycle gas tank cleaner are also available and aren’t as harmful to the surface and its finish.

For best results, combine this method with the one above. Combine the chemicals with bolts and nuts and throw it all in for best results.

Prepare Your Tank

Removal

You have to remove your gas tank before you start cleaning and you can use several techniques for this. The simplicity of these techniques depends on the construction. Some are easier to disconnect than others, but with a little time and skill, all tanks can be removed.

Drain the excess fuel and unhook all the gas and vacuum lines. If your bike comes with fuel valves connected to the tank, you also want to remove those.

Disconnect all the valves, sensors, and lines from your tank as well as bolts that hold it in place.

Plug Holes

You need to block your fuel tank before you put in the diesel and ball bearings. There are several ways to do this, but the best one is to put a short length of hose over the openings. Use heavy clamps to block off the ends of the hoses and make sure everything’s tight and secure.

Unless everything is tightly blocked, the ball bearings and gas will simply spill out. This is a critical step that’s also quite simple, so make sure not to skip it.

Get Some Fresh Air

In most cases, this is best done in the fresh air and a well-ventilated area. You’ll work with acid that can splash around and possibly damage some stuff, so it’s good to be in an open space.

Also, you might have acidic fumes accumulate indoors. If you’re working with a mild acid like vinegar, the smell might not be as bad, but it could result in headache nonetheless. 

If you don’t have a well-ventilated room to do this in, go outside. Set up a catch basin under your tank to catch if anything leaks. You’ll be safer outside as there’s more air circulating.

Test the Agitator

Before you load agitating substances into the tank, you want to test it. Place a few test pieces into a ceramic or glass bowl to make sure the acid doesn’t have an adverse reaction.

The chances of this happening are minimal, but it’s better to be safe than sorry anyway. You could ruin something or make a mess of the inside of your tank. You could even poison yourself, which is why this test is crucial and shouldn’t be overlooked.

If you’re using vinegar, it’s unlikely this will happen. However, if you’re using anything stronger, the acid could eat the items and turn them to dust.

Add in the Acid

There are a few types of acid you could use, although specialists don’t recommend anything stronger than vinegar. Stronger acids could eat directly through the metal construction or at least damage the paint. There’s also the risk of personal injury.

While household vinegar isn’t the most fast-acting, you’ll probably have to top the tank off and let the vinegar sit for a few days. Though it takes some time, this acid removes rust quite gently and won’t damage the tank.

If you do opt for something stronger, you have to protect the paint and of course, yourself. Make sure to have a garden hose at hand, as well as a base in order to neutralize acid if you see it on the paint, other items, or yourself.

Vinegar might not be enough to deal with some tanks, but muriatic or phosphoric acid are typically strong enough. They don’t require any sitting time either. With these acids, you want to add the agitator as soon as possible since they start etching the tank immediately and you need to act fast.

Whatever acid you go for, make sure to be careful. You don’t want to damage any parts or the pain of your tank. Also, protect yourself in order to prevent any possible injury, especially if you’re working with stronger acids.

Add in the Agitator

Once you’ve chosen your mechanical abrasive and you’ve made sure it matches your preferred acid, you can move on to the next step. Add your hardware, BBs or metal screws inside the tank. Of course, smaller is better since larger bolts will most likely dent it.

Here’s our guide on how to remove the dent, just in case you do.

It’s important not to add too many of these bolts and nuts because they won’t be able to move around well enough. You don’t want the tank to be packed full. Instead, add a handful or two since it’s all you need to knock off the rust.

It might also be a good idea to count the pieces you throw in. This way, you can be sure you got them all out once you’re done. It’s a bit tedious, but you don’t want any of those bolts and nuts left in the tank after you’ve emptied it.

Shake it Up

Once all of that is in, you want to shake the tank. Use both hands and shake intensively. You can open the tank as many times to see how things are looking inside.

Repeat the process as many times during the day. Shake it and then leave it for a while before shaking it again. This applies only if you’re using vinegar or another slow-acting acid. Whatever you use, make sure not to leave it in the tank for longer than recommended.

Keep in mind that you shouldn’t leave it out if the temperatures are freezing. You risk rupturing it this way.

You can use other methods to shake the tank a few times a day. Some people would wrap the container in blankets and duct tape them in place before sticking them in a dryer with no heat on. Use your imagination and figure out a way that works for you.

Repeat the process of shaking as many times as it’s required. Keep checking the inside to see how the progress and whether you should continue stirring it. How long this will take depends on how rusty your tank is. Advanced levels of rust require as much as several weeks of constant shaking.

Again, if it’s a highly abrasive acid, make sure not to leave it in for too long because it can eat up your tank.

Flush Completely

Before you flush, you want to heat a five-gallon pot of water on a hotplate or a stove. It has to be quite hot and uncomfortable to touch, but it doesn’t have to be boiling.

Once the acid worked its magic, and everything looks bright and clean, you want to remove the caps and plugs. Throw the acid out into a waiting bucket, but make sure that acid won’t damage it.

Empty the bolts and nuts along with acid and get your garden hose flowing. Get all the acid out, shake it, and make sure the water goes all around the inside of it. You might get all wet, but it’s crucial to rinse it thoroughly.

Put some dish soap to neutralize the acid and add hot water you’ve previously heated. You want to neutralize that vinegar left in. Hot water helps with this, and it will drive moisture off. Now you can empty the tank for the last time.

It’s time to get air flowing through the tank by using a hair drying or a heat gun. Use caution because a heat gun can severely damage the paint job (and you’ll be especially cautious when you find out how much paint jobs cost). It’s essential you use low heat while keeping the gun moving. Use your fingers to feel the material that it doesn’t get too hot.

If you don’t move quickly, you’ll probably see rust reappearing. This is referred to as ‘flash rust’ and is something you want to avoid by working quickly. Still, don’t stress this too much since flush rust is pretty fine, so even if some is left, your fuel filter (see our top picks) will most likely catch it.

Flushing is something you want to be quick with but also make sure to take your time. Flush as much as it’s required until you’re sure that all acid and whatever debris are gone out of your tank.

image of steel motorcycle gas tank with no rust

Finish with a Sealer

At this point, you should choose a sealer to finish the process with. Commercial sealers are an option, and people mostly opt for those. However, some argue that if your tank needs a sealer, maybe you need to replace it. Either way, it’s up to you to decide. Commercial seals tend to go soft and bad after a while, so other options might be better for your carb.

There are several ways in which you can seal up the metal. One of the popular methods is by using a fuel-soluble sealer. Toss some kerosene in your tank if you’ll be reinstalling it immediately. Seal it back up and shake it around to coat the interior thoroughly. This helps prevent flash rust from forming.

On the other hand, if the tank will sit on the shelf for a little while, you might want to use something a bit thicker. Motor oil is an option, and so is tacky two-stroke oil depending on your preferences and what you have at hand at that moment.

Don't Forget the Fuel Cap Gasket

At this point, you want to replace your fuel cap gasket as well. It might seem unimportant but think about it for a little. If your tank was in bad shape, the gasket probably is just as well.

Future Maintenance

An excellent way to maintain your fuel tank is by keeping it full and using the bike regularly. Full reservoirs always displace air that’s required for the rust to form. On top of that, frequent use keeps the moisture out of the air.

The fuel inside will move around and knock all the naturally forming condensation. Use burns that, allowing you to refill the tank with fresh fuel.

If you have to store the bike (see good shed options here) along with the repaired tank for an extended period of several years, you should drain it and do the entire oiling process again.

You might want to consider filling the tank with oil to protect it (see top oils). This means you’ll have to drain it further down the road, but the oil will keep the rust away, and it’s one of the best ways to protect the tank.

Also, inspect your tank now and then to make sure no rust is forming. If you do notice some, it’s recommended you don’t wait for too long to eliminate it if it’s at all possible.

Additional Considerations

Acid Safety Notes

Working with acid is always risky, especially if it’s a stronger type you’ve chosen to work with. As we said, vinegar probably won’t harm you as long as you’re in the open air or a well-ventilated room. 

Regardless of what you work with, and especially if it’s a strong type of acid, you should wear protective gear. Goggles and industrial gloves keep you from getting hurt. These keep your skin and eyes protected from direct contact with acid.

You should also wear a face mask because acid evaporates. If you spend too much time inhaling it, you can end up with headaches.

Make sure to have fresh water at hand at all times. If some acid comes into contact with your skin or eyes, you have to rinse the area with fresh water immediately before seeing a doctor. It can cause burns and scars, so it’s highly advised you do wear protective gear.

You also want to protect your bike since certain acids can damage the paint finish. If that happens, the value of your motorcycle will drop, so it’s definitely something you want to avoid. Again, use fresh water to rinse the area if some acid droplets found their ways onto the paint job.

Additional Chemical Safety Notes

Acid isn’t the only potentially harmful chemical you’ll work with. It’s highly likely you’ll be draining fuel as well. Fuel produces toxic fumes, and it’s important you’re cautious when working with it.

Use caution when dealing with all the chemicals in the process of cleaning your gas tank. Make sure to also dispose of them properly, so that they don’t harm another person or the environment.

Conclusion

At this point, you probably understand the process and are ready to clean your motorcycle gas tank by yourself. It takes some time, several tools, and also some patience, but the result is rewarding.

As long as you stick to the steps we’ve mentioned above without skipping any, you should be successful depending on the rust and dirt level you’re dealing with.

Whatever you do, make sure you’re safe and protected. Keep the air flowing through the room you’re working in or even better, work outside. Don’t forget to also dispose of all waste adequately.

Cleaning a motorcycle gas tank can be a fun process that’s generally simple enough to do at home. If you do come across some difficulties that we haven’t mentioned in the article below, we recommend you consult with a mechanic or another motorcycle specialist.

Additional Resources

The team at Road Racerz aims to be a source of knowledge for all riders, whether they are beginners, intermediate, or have been riding for 20+ years. We want everyone to enjoy safer rides and have access to rider-specific content to get the most out of every mile.

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