That is a good question.

I don't believe JB Weld and Phosporic acid with have any problem - but unfortunately JB Weld does not hold up to exposure to gasoline.  It will break down over time and get gooey.

The best way to fix those pinholes is to clean up the metal - dent them in just slightly with a pick or nail, and solder them using a good flux for steel and solder without flux.

strang wrote on 10/27/15 at 03:10:41:


With this E10 ethanol fuel today....just about every steel tank should have some kind of lining applied - especially vintage tanks that have gone through some rusting previously.  Once the tank has had some rust inside it is very hard to stop it from rusting again.

The POR15 is a good sealer....the Caswell Plating kit is good as well - but does require a warm shop when you use it.  If the temperature is too cold it is really thick and hard to make it move around inside the tank.

I went with por15 as Caswell isn't distributed as widely here so is more expensive.

The badge areas seem to be the worst affected areas on the tank by far, rest of the tank looks like just surface rust, the badge area has dimples where the rust has penetrated. These jap badge mount areas are just stretched to make the indent and so are very thin to start with. Dumb.
  I tried tig welding the hole at first and that was a no go and made the hole bigger, even with the welder on the lowest setting. I managed to weld it up again but it aint pretty. Me dumb.

  I've now managed to get access to a good propane torch setup so I'm considering doing this:
- cutting out the badge mount areas.
- cut metal patches to fit the badge areas.
- braze on new patches using "fluxed silicon bronze rods":
http://www.ebay.co.uk/itm/171952756962?_trksid=p2057872.m2748.l2649&ssPageNam...
- line inside with POR15 sealer.
- finish outside with 2k.
Does this seem sensible?

I don't care about the tank looking slick, ascetically I want the bike to be like the old speedway bikes that me and my cousins used to watch when we were kids in 1970s Australia - so a bit patched up is cool for this build.

thanks Dave very helpful as usual.

Is this flux ok (I have some already)?
http://www.ebay.co.uk/itm/171939397445?_trksid=p2057872.m2749.l2649&ssPageNam...

Was gonna buy this 60/40 solder:
http://www.ebay.co.uk/itm/Solder-Wire-Lead-60-40-40-60-High-Grade-Lead-Free-G...

Here's a video I found of the process. He seems to get good results:
https://www.youtube.com/watch?v=watHkrMQQOs

strang wrote on 10/28/15 at 14:00:45:



The flux doesn't look like it is suitable....the listing states: Metals this flux can be used on.  Copper, Zinc Coated, Nickel plated, Silver etc.


What you want to find is an "acid flux"....not rosin.  Do a search in your area and see what you can find.  I got mine at Graingers....most likely you will need to go to an industrial supply, really good hardware store, or get it online.  My flux is a liquid and I apply it with a Q-tip.

I looked at Youtube and was surprised how badly most of the folks are at soldering steel.......most of them to a really sloppy job.  With a little practice you can do a much better job than they do in most of those videos.  The solder is pulled toward the heat, and a much better job is done if you heat the part and melt the solder by placing it on the heated part.....don't hit the solder with the torch flame or it just melts and drops onto the floor.

This guy does a really nice job of soldering....however you aren't going to have to heat up this much of an area.
https://www.youtube.com/watch?v=LIkvP55UbxM

For the small area/joint you want to do....you won't need nearly that much heat.  The cool thing is that it is easy to practice this....some scrap metal, the flux and solder, a torch...and you can practice.  You can find good solder at flea markets and yard sales - you want acid core or solid solder (rosin core doesn't work on steel).  Solder is not good at filling wide gaps - but it will work on small holes.

Centre stand fully functional - ended up making the spring adjustable.