Agreed, the rectifier doesn't seem like the cause. If you started with a charged battery, you should be able to run quite a while, even without charging from bike's charging system. In your first post you mentioned your battery - did you replace it? Your symptoms are similar to my CA102 Super Cub when it has an older 6-volt battery that won't hold a charge.
Maybe Spokes can weigh in on this, since I haven't completed my CA95 and have no experience with it yet. From what I can see from the CA95 ignition switch diagram below, the alternator/rectifier (charging system) aren't even activated on this bike unless the ignition switch is in position III, with the headlight on. Is that true?
Anyway, when my Super Cub battery is old and only holds about 4.5 volts, the symptoms are similar to what you're experiencing.