A buddy brought me a motor from his golf cart that wouldn't run. Opening it up revealed that one end of the field winding had come unsoldered from the bolt head that served as a terminal. The bolt was brass, and the field winding (not really wire, but insulated bar material about 3/16" square) appeared to be copper, with the end nicely tinned. After a few unsuccessful tries at soldering it with 60/40, I realized that the winding was not tinned copper, but aluminum! What solder and flux (if any) should I use to solder these two dissimilar metals together. I'm using a Henrob O/A torch with its smallest tip.