Battery not charging...?

Ok, so I took some readings with a voltmeter to troubleshoot this battery charging issue. Here's what I got, taking readings at different places:

A. First I put the voltmeter in line with the battery (connected to the positive terminal) in order to test the charging system output. The voltage was: 3.5v at idle, 4v at 2000 rpm, and 5v at 6000 rpm. So it never put out enough to charge the battery.

B. Second, in order to see if the magneto/alternator was the problem, I took a reading at the yellow wire going INTO the regulator (in other words, BEFORE the regulator). Voltage was: 6.5v at idle, and 10v at 5000 rpm. Quite a bit more! I assume that means the alternator is working just fine...

C. Third, I took a reading at the rectifier terminals (the red and white wires on the bottom of the unit). The RED terminal had the SAME readings as the battery listed above (A.). But the reading at the WHITE terminal was different: 0.9v at idle, 3v when I rev the engine with lights OFF. If I turn the headlight ON, the reading dropped down to -.04v.


What I am confused about is:
1) REGULATOR vs. RECTIFIER: does the regulator just regulate voltage to the headlight (and has nothing to do with the battery at all)? And does the rectifier just convert AC current to DC for the battery? Or does the rectifier also limit the voltage coming from the engine so it doesn't overcharge the battery?
2) Given my readings, should I try replacing my rectifier, since my headlight works fine but my battery doesn't charge?
3) Lastly, can you tell me what the red and white wires coming from the rectifier are? The red one is getting the same power as the battery, so I figured that went from the rectifier to the battery. The white one is getting just a tiny bit of power and it seems to drop when I turn the headlights on, so I figured the white was going to the headlight. But maybe I am wrong, and this is all pointing to an issue that I don't understand.