Mower Man Chris got me in to this as well. Gus' (switch) bike was originally a heap that I found stashed away in the shed of a house I rented a while back. Chris gave me an old cruiser of his that his motor was on at first and then I gave this one to Switch.
Chris, Gus and I are all part of an SAE Baja team that builds off-road vehicles using 4130 tubing ranging in wall thickness from .065 to .035. In other words, we have some experience welding thin wall tubing.
Gus welded it with a Lincoln TIG and ER70-S6 filler wire. It should be just as strong if not stronger than the original brazing.
The bike in it's original condition: