Hey, this may seem like a noob question, but how to you fully empty a gas tank?  Thought I got it all but I still here stuff swishing around.
The gas that did come out was brown.  I attached some pics to the inside of the tank, should I be concerned?

Thanks for the help!

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Okay, so I learned about Phosphorus acid, there are some great products for removing tank rust.  But how to empty the tank? Remove the petcock and keep shaking? It's frustrating when nothing comes out but I hear liquid swishing around.

I used this stuff called metal rescue and it worked like a charm. What I did to drain it out was drain as much as possible then dilute with fresh gas and drain again.

Hook up an air compressor to the filler hole with as good a seal as you can get and blow out the rest of the bulk.  If there's any left after that it'll evaporate and leave from the air passing through.

Thanks for the tips.  Metal rescue came up on some of my searches.   Fire up the air compressor!!!

Some local restorers here swear by vinegar left overnight in the tank. 
Does not help you get the junk our. I would add kerosene in stages or something like that to wash out the junk. I managed to get most gas out by shaking but was never 100%

So I have a related question. I have some rust in my tank and it looks like little "rust dust" particles are getting through the gas line. I am thinking about doing apple cider vinegar to clean it, but will it just rust again if I don't use a sealer like Kreem, or will just removing the rust leave me with an ok tank?

The rust is not severe, similar to the above pictures.

Thanks.

Should not rust if you don't get moisture in the tank , sitting a long time without stabiliser for example.
Use the cheap gallon white vinegar, it's purer and will leave less organics behind. My understanding is that liners like redkote and kreem and por15 are OK if you have pin holes in the tank but put them off as long as possible as they eventually lift  off and be a pain to remove (need to put tank on a flame burner).

Yeah you don't need a sealant if you don't have holes in the tank.

..... Been thinking about particles/small chunks left in tanks.... After shaking and all sorts fail to get them out....

A tyre fitters 'tool' which was often home workshop made comes to mind...

They use it for removing all the little rubber 'frass' that builds up in car and truck tyres of the older type that used tubes... But I think it would work for this also?

An air compressor with some good output is required though.

The tyre fitters ones are normally a piece of 1" PVC conduit with a slight bend on the lower end ... And about 2/3rds way up a air nozzle is inserted into the tubing so it blows air UP the tube..... Creating a vacuum behind it and sucking up all the little bits.... Blowing them out in a fountain of crap onto the floor....

Thinking for a fuel tank maybe a 1/2 inch tube? With a heat gun bend or two in it ... The bends let you wiggle the bottom end around to reach the crannies... And still the air nozzle inserted the same.... Depending on compressor strength/pressure you can shift a decent sized chunk of small crap!

Shaking the tank about till the chunks are down in a wider bit maybe near the petcock would make for better aiming with the bottom end too.

Just a thought!

Also .... Working on this same premise.... A well sealed air nozzle into the tube, then a hose on the end of the tube that goes to a fuel drum ...could probably suck the fuel out of the tank fairly quickly too!! ... And it's only air pressure... Only thing I can think of that might be a drama is static ... But having the drum, compressor etc on the ground, or grounded out with a cable like the fuel tankers do while unloading into ground tanks... Would work wouldn't it?

it'd be great to see a cross-section of the tank.  no matter how much i think i got out, there's always a little more in there....

I actually cleaned the tank out this past weekend. The reason you're having an issue getting the rest of the fuel out is because the tank has edges around the sides where the petcock hole can't reach.

I was able to get 99% of the fuel out by rolling the tank in my arms, basically reaching out with the tank (holding each side long ways), and then going down in a rotation to push the gas out of the tiny petcock hole. Make sure you take the petcock out first.

I washed the tank out with water and then filled it up with a gallon of white vinegar overnight. The next morning I drained most of it and put a bit of baking soda to neutralize the the acidity of the vinegar. After that I washed the tank out again and then sprayed a bit of WD-40 into the tank (at different angles) to remove all of the water. It took a bit of time but the bike started up better than ever.

I also used some Seafoam in the tank after it was fresh to help remove the additional potential waste, but I can't comment on how well it worked because I have no idea.

Shake it out, or heat up the tank (leave it in the sunlight), with open gas cap, for it to evaporate.

If you have an inline filter, it will filter out the biggest rust particles.
The rest (brown colored gasoline, without texture or grain), will just pass through the carburetor and burn up.

I wouldn't worry too much about it, but an inline fuel filter is certainly a necessity (I find).
I have that on all my bikes!

thanks for the advice.  i think i got most of the rusty gas out, letting the rest evaporate. i only drained the tank because it's a used bike and after watching all the repair shows on velocity it seems the first thing they do.  never thought i'd see so muck corrosion.
my only concern now is when i have to get the rust repair liquid out. but i guess a good flush and a full tank w/stabil should do it.

Will the phosphoric acid damage the petcock or filler cap rubber? seems like it would, but i need to get a tight seal to let the chemical do it's job....

I used 5 gallons of apple cider vinegar over two days, and covered the petcock hole with gorilla tape that i heated slightly with a heat gun.  It didn't leak once. I don't know how the tape might respond to whatever acid you use, but it worked perfect for me. You might do a test with the acid and see if the adhesive side goes spongey or if it burns through the tape. Also, I would have a gas can ready to rinse with after you empty the tank. This is my second go at rust removal because I drove to the gas station after the vinegar treatment and that was enough to let flash rust start again. Hopefully this time it stays clean in there. I am pretty new to this whole thing so take this with a grain of salt.

Raven

'Tanks' for all the tips! (get it?)   I did the Rust-Oleaum process yesterday.  Had 2 buckets of clean water on stand-by for diluting and rinsing.  Everything went well except, It's really hard to get the tank completely empty!  Best way is as described above, hold the tank w/the filler cap on top, one hand on front of tank, one on rear, and w/the petcock out, rocking back and forth (away and towards me.) Man, took me a while. 
Leaving in the sun to evaporate was a great idea. Got most of it that way. 
Problem now (there's always a problem) is that now I hear dirt rolling around there.  Rust no doubt. I'm thinking of another rinse to get the loose rust out.

It's always the 'easy' things...



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Why use apple cider vinegar instead of plain? ACV has particulate of its own that becomes one more kind of gunk to get out.

Granted, you can get filtered...still why not plain V?

Better aftersmell?

I used apple cider vinegar because I watched a few videos and read some things online that said it worked better. That and the Walmart here in juneau was out of regular vinegar but had plenty of jugs of apple cider vinegar. I drained the tank and washed it out several times with gas, so hopefully it stays rust free.