Removed and reseated the carbs, this time using YamaGoop (r) sealant, and noting that while the intake spuds are almost identical, the operative word here is almost. The last fellow got the back one on the front and vice versa and got the clamps on wrong as well. All this seems to have eliminated an air leak in the intake so the motor runs much smoother now.
I installed the new stator and a replacement turn signal relay, and while the system voltage is now consistently in the 12.5 range, the turn signals are completely inoperative. Oh well. The final assembly leaks no oil and runs smooth.
Speaking of oil, since I needed to replace it anyway, I got oil and a filter and had at it. The filter is removed by first removing 3 screws on the right side and getting behind the cover. All 3 screws are different lengths, and all 3 were in there to the point that a cheater bar was required on the allen wrench. The first 2 came off with a scary pop as the threads broke loose, and the 3rd one gave me a wallered out screw head. No sweat, I'll drill the head out. Which I did after ruining 2 otherwise nice drill bits. A Cobalt bit from Ace Hardware finally did the job. The recalcitrant screw turns out to be an M6 x 95mm Socket head.
Ace Hardware doesn't have anything this long. Neither does the bigger, fancier Ace. Nor does Fasteners Inc who normally have everything. As it happens, neither does the Yamaha shop although they say they can order the screw from New York. The friendly local motorcycle salvage yard didn't have one either but they did have one about 5mm shorter which turns out to get me about 3 turns into the threads. By 3 PM Friday it looked like my last hope was a metric specialty shop conveniently located on the opposite side of town. Maybe Monday.
Last things to address are the gas tank which had the egg-shaped filler neck, and the front tire which refuses to seat on the rim. If I can beat the tank back to some semblance of round, I believe the flip-top cap the previous owner bought will snap in and out and do the job. This will be tricky. I may farm the tire job out and attribute this to laziness.