Yes, John is correct about step 1!

I then gave it a couple of flush outs with a splash of car wash detergent and water, then I actually used a jig-saw to cut the filler neck out etc.
I then left it for a day before using the oxy-acetylene to stretch the front section out. The key I think is to leave it for a while to let the vapours from the metal air out.

The last thing to do, if your not sure, is to drop a match inside while wearing a welding glove!

TBA, Stainless extractors / drag pipes, 65mm over forward controls, Thruxton needles, 904cc, head ported, lowered 1-inch, Console removed, relocated battery box, Australia.