As our ladies are aging I have seen this problem more lately - especially with high mileage and from locations with a lot of corrosion. I have repaired several OEM exhausts that had broken welds where the header tubes enter the muffler can - in conjunction with a glasspack mod. This is for exhausts with broken welds, not broken pipes further upstream - broken welds is almost always the problem on this issue. How it's done properly, is to put the pipes on a custom jig which holds the relationship between the headers and muffler can in the OEM position. Tack (MIG) weld it on opposite sides of each header pipe, to the muffler can. Honda's welds on the exhaust are MIG - TIG is pretty but not necessary and MIG is strong and fast. Put my usual scribe marks around the perimeter of the muffler can and cut it apart about 3/8" downstream of the weep hole. Throughly weld the ends of the header pipes inside the muffler can - where the headers were welded in the first place by Honda. Welding on the outside where the pipes enter the can is inadequate as you cannot weld towards the middle between the pipes. Also you MUST have a jig already set up to align the headers to the can correctly. With this procedure the weld junction is much stronger than Honda did it.
The headers are carbon steel while the muffler end plate is SS. I don't know the alloy.
After the weld repair, I then continue with a glasspack mod. That is, weld in my custom header collector (with a crossover nipple if that was ordered) before welding in a glasspack and re-welding the muffler can back on. And adding whatever other options were ordered. There are of course more procedures needed that must be done for the assembly to be valid and for it to fit back on the bike. This is just a brief summary of this repair.
Inside view of one of these repairs:
