How to acid clean a tank while it's still in the frame

[Placerville]

Fast and Furious - How to clean your tank with Muriatic acid while it’s still in the frame

Before you start, here’s some common sense: Hydrochloric acid, commonly called Muriatic acid, is a highly corrosive, strong mineral acid. Direct contact with soft tissue, such as your eyes, mouth and sinuses, will cause immediate irritation, burning and possible permanent damage. Inhalation of Muriatic acid fumes can cause sinus and/or lung damage. Although this product is readily sold to the general public, it comes with a warning on the container. Read the warning and follow the manufacture’s advice. Use due diligence and you’ll be fine.

Cleaning your tank with Muriatic acid is a very fast, affordable and effective way to remove rust. There are other methods of removing rust from your tank’s interior while it's in the frame e.g., EvapoRust, citric acid, toilet bowl cleaner and vinegar. All of these methods have been discussed on this board. I suggest you research them so that you’re able to decide which method is right for you as this thread only discusses the use of Muriatic acid while the tank is in the bike.

Now that the formalities are out of the way; here we go:

Materials you’ll need:

1. Five gallons of real Muriatic acid. (Buy the kind that’s sold in pool supply stores or other outlets. Do not use the type that’s found e.g., in Home Depot that’s labeled 'safe', as it's not powerful enough and won't work properly. Do not dilute the acid, you must use it full strength.)
2. An inexpensive siphon found at most auto parts stores.
3. Two five gallon plastic buckets.
4. A box fan or other good quality ‘air mover’.
5. A 1.75" expanding plug (available at any auto parts store)
6. A section of wooden dowel or other non-metallic stirring device.
7. Some painters plastic, tarps and some old T shirts.
8. A working garden hose near your work area.
9. A 3 ft. section of rubber hose that will fit your petcock.
10. A shop vac with the hose reversed and plugged into the ‘blow’ hole.
11. A 1' long piece of heavy gauge copper wire.
12. Gloves and eye protection. If you wish, a mask suitable for filtering chemical fumes.
13. A new petcock (or rebuild kit), new fuel lines, new filter and fuel sending unit gasket. All found here.


To begin:

Siphon the fuel from your tank. Remove your fuel sending unit and set it aside (more about this later). Put the expanding plug in the sending unit hole and snug it down. You do not want this to leak or pop out. Close your petcock and disconnect the fuel line from it's nipple.

Next, drape your entire bike from end to end with heavy painters plastic. Cut an opening in the plastic for the tank's filler neck and sending unit hole to poke through and tape it down. Now, cover the bike with a tarp and seal off the area between the tank and frame with heavy cloth. Add a few old T shirts around the filler neck to catch any spills. When you’re done, all you want to see is the tank’s filler neck, the expanding plug and a lot of tarps. Now, set up your fan so it’s blowing at your back, positioning it so it will blow fumes away from you and your work area.

Now, with your two 5 gallon plastic buckets, your bulb siphoning pump nearby and your fan running at your back, pour Muriatic acid into the tank until it comes to within an inch of the bottom of the filler hole, not to the top of the neck rim. The action will start immediately. It's not violent, but it will be obvious that something's working.

Depending on the level of rust in your tank, leave the acid in for as little as 10 minutes for minor rust, or from 30 to 40 minutes for heavier rust. As the acid is doing its thing, insert a wooden dowel into the neck opening and stir. This moves the stronger, undiluted acid from the center of the tank towards the rusted areas, improving the action. When you feel that you've waited long enough, (use your best judgment), siphon the acid from the tank into a 5 gallon pale. Set the pale aside and cover it to reduce the fumes. (A piece of plywood works well.)

Using a garden hose, fill your tank with water and siphon it out into the second bucket. Set that aside (no cover is needed). Remove the expanding plug and siphon out the remaining water. Now, using a small flashlight, illuminate the tanks interior from the sending unit and filler neck openings. (It's helpful if you have some type of small inspection mirror on hand for this.) It will be obvious that you've made progress but, if you still see rust, replace your plug, pour the acid back into the tank for an appropriate period of time. Repeat until your tank is spotless. To get the acid back in your tank, pour an amount of acid from the 5 gallon container into a small plastic bucket, then from the bucket into the tank via a plastic funnel. Obviously, you would not want to attempt a straight pour from the 5 gallon container into the tank.

When you've determined that you've dissolved all of your rust (and you've drained the acid from the tank), begin the rinsing process. Reinstall your expanding plug. Using a garden hose, fill your tank and drain it two or three times. Let the hose blast into the interior from the filler neck during this process. When you've drained it for the last time, it's now time to ensure that your tanks main and reserve lines are clean.

Remove your petcock and set it aside. Using a length of heavy gauge copper wire, run the wire into each tube repeatedly. If it comes out very clean, most likely your tubes are clean. But, if you get any residue, do this: Reinstall your petcock. Place the 3 ft. section of tubing on the end of your petcock and with the other end in a plastic bucket, open the petcock. Pour enough Muriatic acid into the tank to cover both the main and reserve openings. Reinstall the plug. Place the end of the shop vac hose into the filler, seal the opening with a rag and blow a little air into the tank. This will cause the acid to move into the lines. Turn off the petcock to stop the flow and let it set for a period of time to dissolve any residue. Rinse the tank again. Install your new, or rebuilt, petcock.

To remove any water that’s left in the tank after rinsing, suction anything you see out through the sending unit hole. What remains in your tank is a very small amount of moisture. Do not attempt to dry your tank with a heat gun as this may cause flash rust. Do NOT use Acetone to rinse your tank as this WILL cause flash rust. A small amount of moisture left in your tank is of no consequence.

Now, for your fuel sending unit. This unit is delicate. It has small wires inside that can break easily. To clean this, I recommend that you purchase a quart of EvapoRust. EvapoRust removes rust without acid and will not harm the this units wires.

To clean the sending unit, bend up the three tabs that hold the little cover to the unit and remove it. Inspect the interior. Specifically, look to make sure that the wires on both ends of the winding are intact and soldered to the 'hot' post. Pour the EvapoRust into a glass container and submerge the sending unit and its cover. It's not necessary to submerge the float arm or the float. You can clean those manually. Leave the parts in the EvapoRust until all of the rust is gone. This could take only 30 minutes or up to 24 hours depending on it's condition. When done, rinse it with well with water, spray it with WD-40 and put the cover back on.

Reinstall the sending unit with a new gasket. Don't use Permatex. Coat the gasket with a thin film of light oil. A tip: To ease the installation of the sending unit’s metal closing rings, lubricate all mating surfaces with a bit of oil.

Regarding the disposal of Muriatic acid: Muriatic acid goes completely inert when it comes in contact with soil. As a result, you can dispose of it by pouring it into the ground. Do this in an area where there will be no direct contact with surface vegetation e.g., flowers and tree roots. Broadcast it over a wide area rather than in one place. If you’re not comfortable with this method, your local landfill can recommend a disposal method.

One last thing comment: When you clean your tank, choose a time and place when you can accomplish your task with ease and not feel rushed. Have all your items at the ready and set up ahead of time so you're not running around at the last moment trying to find something. And, by all means, make sure that no children or pets will be in the vicinity.

Update: I've recently been very impressed with EvapoRust. Although it's much slower than Muriatic acid, it's very thorough, can be used several times, has no fumes, is completely 'green' and, best of all, it doesn't remove any of your tanks metal in the process. (Consider the benefits of that last comment.) However, it's expensive. To do your tank, it will take one 5 gallon container plus two additional quarts. About $120.

[Roady]

Most excellent, Sir.
Thank you very much for that.

[Whiskerfish]

[gltriker]

I saw no mention of a generous quantity of baking soda immediately available in the event of an emergency, to neutralize the Muriatic acid. Especially, if 5 gallons of pool store supply strength Hydrochloric acid is used.
Just saying...... you can't be Too prepared.

[sunnbobb]

Good point, safety first! lol

[Track T 2411]

Just an FYI on muriatic acid strength, at least here in Wisconsin. Pool supply houses sell muriatic acid by the gallon, labeled as 31.45% hydrochloric acid. Home improvement stores such as Menards sells the same product, same strength, as well as the "green" product, which is less concentrated, as Placerville mentioned above. I did mine earlier this year, before I found Placerville's write up, and actually diluted the acid considerably, causing an extended session...

[tlday]

I did mine last year and after draining the muratic acid I mixed a solution of washing soda in a quart jug of water (about a half cup of soda and the rest water). Then, I dumped the washing soda mixture into the tank and finished filling the tank with water and let it set for a couple of hours. This neutralizes the acid in the tank and prevents the flash rust. Then, after draining the washing soda solution from the tank I dried it with a heat gun held into the neck of the tank. The warm flow of air will remove the water from all cracks and crevices.