Cleaning old.gas residue

[Monzadude]

What is the best way to clean old gas residue out of a gas tank. Also to flush out the gas lines. I've read lots of different ideas online but was wondering what you guys recommend.

I got a new fuel pump but won't install it until everything is cleaned first.

[classic_cruiser]

I'm no expert on this, but I've used acetone in metal fuel lines and all metal tanks with success - let it soak in the sealed tank overnight, or fill the fuel lines and let them sit overnight capped (both outside, of course - not in the house!). The next day, dump it into a clear glass jar and see if it comes out clear - if not, repeat. It helps if the temperature when soaking is warm - sunny day in summer.

If the residue is real gummy, an abrasive slurry like small gravel (even something as big as #2a modified driveway stone) and water sloshed around in the tank for a while works pretty well. You have to dry it well to prevent rusting - a phosphoric acid treatment afterwards helps too.

I wouldn't do this on the newer tanks with the plastic baffles in them though.

[Monzadude]

I tried the acetone in the gas tank. It's still cold out here but it seems to be working well. It turned black in no time. I've dumped it out and put more in it. I'll check it in a day or two and see how it looks.

[classic_cruiser]

Just be careful that the tank doesn't start rusting if you leave it in that long. Acetone has some water in it.
If it's really stuck on, the method with the slurry abrasive might work better.