Frank, I bought a kit, brand named Kreem at a motorcycle shop. It comes with etchant/rust eater, rinse to neutralize that, and liquid plastic to coat inside of tank. If yoiu do it right this lasts well and can be renewed with a MEK rinse and more liquid plastic if you need it years down the road.
1. First I used "Spic 'n' Span" to degrease inside and out with drill mounted and manual wire brushing on outside.
1.1 weld hole with wire feed gun turned way down and using flux cored wire. (this is not easy, I took 4-5 hours)
1.2 braze the weld to seal porosity of poor weld (my first attempt at brazing, not a pretty thing)
2. Next you etch inside with their chemical (I bolsterd mine with a commercial rust remover/metal prep based on the active ingredient of Naval Jelly). Did this as you need to completely fill tank to do good job and the dilution would have been too great.
3. Wait for it to work, pour it out but save it in plastic waste cans. Inspect inside for residual rust, put a handful of nuts and bolts in the tank, pour liquid etchant back in and tumble the tank by hand.
4. Repeat step 3 above as needed till no rust.
5. Rinse and drain
6. Add their rinse agent (MEK or acetone or some other highly volitile solvent known to the state of California to cause cancer, warts, or both. It is fully miscible with water and removes the last of it.
7. reverse shop vac and blow dry the inside. (do not use hair dryer, explosive fumes)
8. pour in plastic and turn tank everywhich way.
9. pour out plastic and let tank dry.
10. repeat 9 & 10 a few times to build up a thicker coating.
11. let dry
12 paint outside with heavy rusted metal primer (red)
13 paint outside with spray-on undercoating (black)
14 paint outside with hammertone rust encapsulating dark grey paint.
15 reinstall
16 pray it doesn't have to be done again in your lifetime.
I found that what I thought was a on/off petcock where the fuel leaves the tank was in fact the original Wolfsberg "gas gage" In other words the manual reserve valve. It has two litle brass fuel pickup tubes, one about a couple inches longer than the other. Switch the dual port valve to the position that draws fuel from the taller tube. When you run out of gas, switch to the other pickup tube and you can access the rest of your gas. The original VW beetles had this in lieu of a gas gage. There was a manual torque rod on the fire wall that you twisted to remotely operate the described valve. As my shorter pickup tube was glogged with "cruddygunk" the valve acted like an on off petcock. No wonder I thought I was getting poor mileage. I never used all the fuel in the tank before "running out" and dumping in my reserve from a small plastic gas can I carried (stranding in Baja is not just inconvenient but can be life threatening)
Bubbble gum and bailing wire will fix a lot of stuff.
The hole was a dent with a "star" shaped series of radial cracks from the steering damper mount pounding on it for years. When I adjusted that part of the tank with a large hammer to shape that area away from the dangerous damper, the gcracks opened up to a bunch of really enormous gaps. Welding was done with the tank full of water but inverted/positioned to place a small air bubble at the weld site. As I have always done before on jobs like this, as soon as you are 99% done you burn through and have another 1/4 inch dia hole to fix etc. etc. etc. The effort and perserverence builds character, I'm told. If I had it to do over, I'd solder it in 5 min and color it done. If I were really smart I would not have dented it in like my mechanic/consultant directed but reworked the damper mount (custom by crunch, with a big hammer) instead.
Patrick
