How I clean steel motorcycle gas tanks

First let's CYA:

Gasoline is flammable use proper precautions when working with gasoline.

Hydrochloric Acid ( Muriatic Acid )is very corrosive, wear gloves, eye protection and a protective

apron when working with acids. NOTE: ADD ACID TO WATER, NEVER ADD WATER TO ACID. Here is part of the caution label:
Label Hazard Warning:
POISON! DANGER! CORROSIVE. LIQUID AND MIST CAUSE SEVERE BURNS TO ALL BODY TISSUE. MAY BE FATAL IF

SWALLOWED OR INHALED. INHALATION MAY CAUSE LUNG DAMAGE.
Label Precautions:
Do not get in eyes, on skin, or on clothing.
Do not breathe vapor or mist.
Use only with adequate ventilation.
Wash thoroughly after handling.
Store in a tightly closed container.
Remove and wash contaminated clothing promptly.

If your tank is rusted through. Removing the rust will make it leak! In theory sealing your tank

will prevent pinhole openings from leaking. Don't bet on it. Unfortunately if your tank has rusted

through it's probably junk.

This procedure is meant for steel tanks only. Do not use this procedure on aluminum, fiberglass or

plastic tanks.

Phosphoric acid is preferred however it is often difficult to find. Hydrochloric acid is available at

most stores that sell pool supplies.

Tools and materials: adequate tools for removing your fuel tank,apron,baking soda,flashlight,

gasoline, gloves, goggles,water hose, Hydrochloric Acid or Phosphoric Acid, power washer or a pocket full of quarters.

Now let's get started.

1.Remove the fuel tank per your service manual instructions.

2. Shake the tank with the old gasoline inside. Turn it over and pour it out into a clean container.

3. Examine the gasoline. Look for water, rust and large amounts of particulates.

4. Using a flash light (NEVER USE A FLAME SOURCE) inspect the inside of the tank. If the gasoline is clean and the inside of the tank is clean and rust free. Rinse it out with a quart or two of fresh

gasoline. Then reinstall the tank.If the old gasoline is dirty, contains water or rust or a visual

inspection of the interior of the tank shows signs of rust or contamination proceed to step 5.

5. Remove, disassemble and clean the petcock per your service manual instructions.

NOTE: AT THIS POINT MAKE SURE YOU HAVE AT LEAST THREE HOURS TO COMPLETE THIS JOB. IF YOU STOP BEFORE YOU HAVE COMPLETED ALL OF THE REMAINING STEPS YOUR TANK WILL RUST!

6.If the tank is heavily rusted and or contains sludge or particulates wearing the proper protective

equipment, power wash the interior of the tank until all loose rust is removed. If you are using a

gas powered power washer make sure it is located a safe distance from your work area. If you do not

have a power washer available, a self service car wash is a good option. Do not leave water in the

tank for a long period of time. 

7.Cap or plug the petcock opening. If the tank has a crossover tube remove it and cap or plug the

openings.Stop and read the warning labels and MSDS for the acid you will use. Fill the tank about

3/4 full with warm NOT HOT! water. Slowly add about one quart of Hydrochloric acid.ALWAYS ADD ACID TO WATER, NEVER ADD WATER TO ACID! Adjust according to volume. You want to use about 7 parts water to one part acid.In other words; one quart acid for a two gallon tank, two quarts acid to a four gallon tank etc. Avoid getting acid on your paint. If acid gets on your paint rinse it with water immediately. Top off the tank with warm water. Let it set for two hours.

8. Empty the tank, neutralize the acid and dispose of it. Baking soda, lime or lime stone works well

for neutralizing the acid. Dilute and discard the used acid.

9. Immediately rinse the tank with lots of clean water. At this point your tank will almost

immediately start to flash rust. DON"T STOP AT THIS POINT!

10. I recommend treating the tank with a sealer to prevent rust from reappearing. I have used a kit

made by Kreem sucessfully. Some people hate it! I suspect that they didn't follow directions.
Some other options are POR-15,KBS MOTORCYCLE GAS TANK SEALER and others.Follow the directions for the sealer exactly.

 If you decide to skip the sealing step immediately rinse the tank with gasoline, reassemble the

tank, install it on your bike and fill it to the top with fresh gasoline.  
 

A few observations

There are safer more environmentally friendly acids available that may work as well as the two I

mentioned. I know the acids I listed work. The cleaning product Lime Away contains Phosphoric Acid.

However, if you can find concentrated citric Acid it may be worth trying. Oxalic Acid may work as

well.

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