I'm impressed, you guys know a lot about life, welding & metallurgy..! Even more about bikes..!

These factors will help you braze 'n solder better (think % of bond in the joint between the pieces 80%+ is great)
a) Low gas pressures -- keeps the heat from bouncing off the weldment -- oxy 6psi try 3 psi for fuel -- (can't remember BUT LOW pressure works) use a neutral flame
b) Joint fit-up -- keep tolerances close (.003" or less)
c) Clean base & filler metal (sanitary clean)
d) Best quality & proper Flux (clean & thinned with water if needed)
e) Proper torch manipulation (evenly heat the pieces) keep the torch moving

Aloha --
George (one new case Oahu today)