The exhaust fume method of making tanks safe to weld was the favoured way of emergency tank repair in the paddock at race meetings. Probably prevented now due to H&S. A friend who restored Frazer Nash cars had a more exciting method of fuel evacuation, shake out any remaining fuel, blow out with the air line, light up the welding torch and waft it around the filler neck, at arms length of course. The result was a whoosh and column of flame. He never had an explosion, and died of natural causes, but of course I would not under any circumstances suggest that anyone should try this themselves. It could be fatal.
That is exactly what I have done several times in the past with no ill effects. It is also how I mount new modern tubeless motorcycle tires ("tyres"). Fit the tire to the rim, spray starter fluid into the rim space, stand at arms length with an extended barbecue lighter, and it's seated.
I have done both the exhaust till the tank is too hot to hold and its counterpart a hot air gun.
Also the tank filled with water method
This is also a very old thread but worth a mention.
Solder should really be lead wiping rather than soldreing particularly if there are lots of pinholes.
If you go that way the trick is to strip all paint off, degrease then apply a mix of oxide & reducing flux called Panel Butter.
I know Eastwoods still sell it.
That will leave you with a tinned tank that will take solder beautifully either by direct flame or big soldering iron.
I have also done them with silver solder using my Henrob Torch, now called DHC 2000 .
Kent , the tin man ( google him ) does a much cheaper more conventionally shaped torch for those who find the pistol grip Henrob difficult.
I never liked the idea of bronzing a tank.
Bronze has a bad tendency to crack from vibrations
With the Henrob it is possible to weld pin holes with steel, done it many times, it is just a case of getting fine enough feed wire.
I use thin tie wire which is handy because you can put the coil ( donut to some ) of wire over one wrist and feed the wire in as needed.
Practice on some in cans first .
Once you can weld them without blowing holes you are there.
I remember seeing this method of tyre fitting on TV,Top Gear I think, it was being used on a huge FWD tyre in Iceland but I've never seen it used for bike tyres though.
