[Roofaloof]

I've used phosphoric acid with great results.

First used Simple Green (degreaser) and water to clean the gunk out. Then swished some nuts and bolts around to break up the rust.

Then used the phosphoric acid. I used off-brand "CLR". It was $8/gallon at the restaurant supply store. Swishing the gallon of acid around for ~30 minutes cleaned out all the rust.

As a bonus, phosphoric acid etches metal AND deposits zinc on it! This means no flash rust after treatment.

After the acid, I rinsed out many times with water and dried the tank in the oven at 175 degrees F.

I then put a half-pint of POR-15 into it. It's been sitting for 4 days now curing.

Hopefully this will end my clogged tank woes!

 

[JimmyRiot]

I did my first gas tank last week. It wasn't bad in there, and in hindsight I should've just left it alone. I wanted to avoid heavy chemicals cause bike's in basement (no hose either). I did the vinegar thing and hit wicked fast flash rust before I could swish my Marvel Mystery Oil to halt it. It was worse than when I started. I filtered my vinegar & put it back in & read even more on this. I prepped my baking soda water, plain water, all ducks in a row, and I got just one quart of phosphoric Krud Kutter Rust Remover & Inhibitor (Menard's). I also shook a chain around in there.

I dumped the vinegar & RACED to get the base water in, half tank, shook vigorously, dump, round 2 of baking soda water shake, dump, clean warm water shake, dump, then quick w/ the Krud Kutter, swished that on & off frequently for half an hour, poured it in to a pan to soak a centerstand, & dried the tank w/ an air hose on low. It came out pretty good in the end.

 

[rabidawise]

Hey guys/gals, just wanted to throw something out quickly. I am all about DIY, and try my hardest to never pay for any labor that I can do myself. That being said, I work for one of the last radiator shops in the Memphis area, and the only shop in town that cleans/repairs/lines fuel tanks. To remove rust, we either use a sand blaster, or muriatic acid. We use a hot vat of caustic soda to remove fuel deposits, and also to neutralize the muriatic acid. We use Red Kote (which is not always red) liner when we line tanks, and we have had excellent results with it. If anyone has any questions about the process, feel free to give me a shout. If your not comfortable handling the job yourself, we'd be happy to help you out as well!

 

[CL-350 K2]

Does anyone have any feedback on how Caswell Fuel Tank Sealer holds up over time?

I also have a tank with mild tank liner peeling. According to others it looks like Kreem but with a gray colored lining underneath it. The gray lining origin is a mystery. Does anyone have experience using Caswell over failing Kreem and whatever the gray liner is underneath?

Thanks for the advice!

 

[1967 Honda CD125]

I have been using 100% apple cider vinegar in all the tanks I have been restoring. One tank was probably the worst case you will ever see, and it came out beautiful. My steps are:

1. First shake out all the loose scale and rust and crapola as much as you can.
2. Remove the petcock and try to take off the any filters/pipes that might be sticking up. (So they wont be in the way and get abused when the metal washers are bouncing around inside). Clean petcock well, put some oil on the ORing, and put back on. Be sure to turn to "Off". As an added precaution, I attach a rubber gas line and keep it wrapped up above the tank in case the petcock leaks and you loose all the vinegar.
3. Use water to flush out as much debris as you can (before putting the petcock back on).
4. Add 100% apple cider vinegar to the tank, and fill to almost the top. Best to warm the vinegar on the stove. Then, make a spot which has direct sunlight most of the day, and place tank there on a soft surface so you dont scratch the bottom edges. May need to use some blocks of wood to get tank level. Put top on so vinegar does not evaporate out or bird crap falls in.
5. Let sit in the hot sun so the vinegar stays warm (and the 3% acid works better warm) for 4-5 days (depending on how much surface rust the tank had). For a tank with light rust, try 2 days, and for one that you thought about tossing into the dumpster, try 5 days.
6. Pour half the vinegar out into a 5 gallon plastic bucket (you can save this and reuse in another tank, or for rusty bolts). Add about 50 small washers (about 1/2 inch). Then shake real good for as long as your arms will take it. Try sideways, up/down, etc......shake, rattle, and roll.
7. Dump out the vinegar and rust particles into another 5 gallon bucket. Use a flashlight to look inside and judge if it needs to soak more, or if it is good.
8. If all looks good, continue to add water and shake around with the washers, and then dump out.
9. Then add a big cup of Baking Soda to the tank and fill 1/3 with water, and again shake as much as you can with the washers inside. This will further clean and neutralize the acid.
10. Dump out the water/baking soda/washers into another bucket (not the vinegar buckets), and flush again with water. Keep shaking until all the washers are out. For tanks with the flange that goes straight down a few inches at the opening, those washers can be hard to get out.......i found that a magnetic pick-up tool does a good job at retrieving the washers.
11. Then remove the petcock and let as much water drain out as you can, tilting the tank at different angles to get it all out
12. Then take tank to bench, and use a hair dryer to blow warm air into the top, while water drops are forced out the petcock hole. Be sure you tilt the tank to get every drop of water from the other side of the tank (opposite the petcock). Takes a good 5 minutes to blow dry the tank.
13. Then immediately add a gallon of diesel fuel, or motor oil to the tank (after putting the clean petcock back on). This prevents any flash-rusting until you are ready to use the tank.
14. When you are ready to install the tank and use again, just drain out the oil, and rinse with some gas.

Also, its a good idea to put a coat of wax on the outside of the tank to help protect the paint, in case you spill some vinegar onto the paint. When you do spill some, or if the sun heats up the vinegar causing it to expand and leak out the top, you will want to use soapy water to rinse off.

Vinegar is super cheap, and has worked great on all the tanks I have done.
Use a funnel with a filter screen, and pour the vinegar back into the bottles, and you can use it again on another tank, or for rusty parts. Waste no, Want knot.

 

[longdistancerider]

Nice write up of your process, thanks

 

[Old Putz]

So we've got a lot of good advice regarding rust removal, but what to do if the rust has chewed through the tank? Not necessarily time to toss the tank. Surprisingly large holes can be repaired with readily available tools and just a minor bit of work. As with any repair, you'll want to start with a tank that's completely empty of fuel and well rinsed and aired out so that there are no gas fumes. If you've done the rust removal outlined in this thread, you should be in good shape already.

You'll need a reasonably powerful soldering iron, some soldering flux, a brush to apply the flux, some solder of course, and some sandpaper and a small round file:

That's a 140 watt soldering iron. You want a reasonably powerful soldering iron- a 15 or 20 watt pencil-tip iron won't be powerful enough to heat the area thoroughly enough to get the solder to flow out and stick. These are reasonably easy to find at garage sales and flea markets, generally because they've cleaned out grandpa's old stuff and cant figure out what anyone would do with such an oversized iron (grandpa used it to repair the radiator in his Buick, not mount transistors to circuit boards).

I discovered that my tank had holes in it when the paint started bubbling up. The tank had been Kreemed a decade or so back, but from the look of things the rust had begun before that because of spot welds done in the process of pulling dents. The holes were allowing gas to seep into the Bondo, undermining the paint and causing large blisters that reeked of fuel. So I took a razor knife to the Bondo, removing all the softened, fuel soaked filler and exposing the rust spots:

On top of the tank, aft of the filler neck.

Right front corner of the tank (where the tank typically gets bashed if you drop the bike).

Bottom right corner of the tank, where water generally settles (VERY common site for rust-through)

Thoroughly sand the area around the hole. Cleanliness is absolutely critical. It also helps to file out the inside of the hole, as the solder will adhere to the inner edges of the hole. Filing also removes paper-thin metal that will detract form the strength of the area:

Yeah, you'll be making the holes bigger, but it's better to make it slightly bigger if it'll help the solder to stick.

The repair itself is easy to do. Brush some soldering flux around the hole, extending 3/8" to 1/2" around the hole. Get the soldering iron hot, clean off any old solder with a wet rag, melt a bit of solder onto the tip, then place the solder-wetted tip of the soldering iron over the hole. The melted solder will help the heat to flow into the adjacent area. Feed solder to the tip where it meets with the tank- once the area is hot enough, the solder will melt and flow onto the metal. You want the solder to flow out and bond to the metal. If the solder balls up instead of flowing into the metal surface, the area isn't hot enough. The flux allows the solder to bond more completely to the metal and helps with flow out.

When you're done, it should look like this:

Since the first two repairs would be covered in Bondo, I just left them as-is. The spot on the underside of the tank I filed down so that it isn't so obvious:

From there, just continue with filling & sanding the repaired area:

Easy peasy!

 

[krukster86]

What is the general consensus of POR-15? I found an unopened box of the Motorcycle Tank Sealer kit in storage, and was thinking about using it on my tank.

 

[Rob Axel]

Check the shelf life of that stuff before you use it!!!!
Just this month as I am doing a paint job for a local shop... my base coat paint "cracked"... I had never had this happen..using the same stuff for years, never had an issue...
well the phrase "same stuff for years" played a part.. the hardner (with most catilized stuff) has a shelf life... depending on elements some longer then others... I had no idea untill this paint job was driving me nuts, I thought I may have some "contamination"...
Would hate for you to get this tank sealed, then later find out your having to find a way to remove this stuff because the fuel/alcohol may break it down... yes even if it dries and cures.. the catilyst (that keeps it hard) will give way to something as light as denatured alcohol...

 

[krukster86]

Check the shelf life of that stuff before you use it!!!!
Just this month as I am doing a paint job for a local shop... my base coat paint "cracked"... I had never had this happen..using the same stuff for years, never had an issue...
well the phrase "same stuff for years" played a part.. the hardner (with most catilized stuff) has a shelf life... depending on elements some longer then others... I had no idea untill this paint job was driving me nuts, I thought I may have some "contamination"...
Would hate for you to get this tank sealed, then later find out your having to find a way to remove this stuff because the fuel/alcohol may break it down... yes even if it dries and cures.. the catilyst (that keeps it hard) will give way to something as light as denatured alcohol...

O__O

Thanks for the heads up!

 

[drdubb]

Put just over two gallons of Apple cider vinegar in my SL 350 tank. I had previously removed the PO's Kreme and some rust with POR products. Set it in the garage with a lamp underneath and a quilt over the top. I'll let it sit a few days before taking a peak. Baking soda is at the ready as well as some alcohol. Need to pick up some diesel.

New regulator/rectifier arrived today as well as the graphite muffler gaskets. I've had this bike about 5 years, time to get it going and on the street (or trails)

 

[Rob Axel]

Keep us posted.. just took possession of a tank with what the PO described as "typical surface rust".

Last tank I did I used muriatic acid from Home Depot... looked almost as bad, but I believe it was mostly old fuel residue..

 

[drdubb]

I let the tank set with the vinegar five days or so. Worked pretty well. However, its abnormally cold here, so my hose bib was frozen, I hauled water out from the kitchen in 1/2 gallon pitchers to rinse. Used alcohol to rinse the water. Got a little flash rust, but not bad. Remember to turn off the petcock before adding gas. I kept wondering where it was coming from until I had the realization.....

I"m now airing out the garage. I don't want the gas hot water heater to ignite the fumes.

 

[BrianHull]

Sounds like I need to use Evaporust on my tank. How long is idea for a good removal? 24-48 hrs

 

[Rob Axel]

Depends on what you use to clean it.. if ur using muriatic acid... 1-2 MINUTES should be long enough. It will also depend on strength of the solvent (%)....
Just remember to "coat" the tank with a "oil" to keep out the flash rust..

 

[GodZilla]

Not a gas tank but just to show you how what distilled vinegar does, I did this with an old Coke Cooler and a few other things worked awesome but you gotta be sure you have baking soda or whatever to neutralize it after and flush flush after.

The rust basically brushed off after with a soft brush. I have a tank that needs to be done soon but want to try out Evapo-rust and BB's.

 

[mike in idaho]

Got this out of a goldwing tank, using electrolysis:

Inside of the tank afterwards:

 

[ancientdad]

Man, that's a lot of rust there... no holes in the tank at all?

 

[mike in idaho]

No holes, the re-bar I used for an anode got kind of thin on the bottom end.

 

[ancientdad]

Sure did. One day I'll have to try that, it looks like it works amazingly well