The exhaust is silver soldered together, the black flux seemed to work better than the white, cleaned better while soldering and afterwards. The label states it is for stainless so I expect that is the reason. It was worth the $10 investment. The I installed #4 screws though the clamp slot and Teflon coupler the locate the canisters fore and aft and radially. This should keep the canisters in place.
Next up is engine management, i.e., throttle and choke.