Don't trust the Clymer procedure for testing regulator/rectifiers. It will tell you nothing, and convince you that it's bad, even when it's not.
I installed a new reg-rec on my bike yesterday. My old one was crap, and was letting too much juice through. The lights got much brighter above 3000 RPM, and I was blowing dash and turn signal bulbs.
I tested the new reg/rec before installation using the same method you're using, and got really stupid readings. I think that the test procedures make assumptions about the voltage output of your multimeter. The new unit is working fine, lights are even, battery is charging, not blowing bulbs, etc., but according to the multimeter it's not passing electricity no matter how I hook up the meter.
Because you asked, the readings I got were infinite resistance with both positive-to-yellow and positive-to-black, on a unit that's been behaving well for me so far. 1978 D1A (SR). I even replaced the battery in my meter, thinking that it was the culprit. I think it's just that newer meters with solid-state components are much more sensitive, and don't put out the same amount of power as the older equipment.
Rectifiers cause a constant voltage drop (1.4V for some common diodes, for instance), as opposed to resistors for which voltage drop depends on current passed. If the meter isn't putting out enough voltage to reach the conductance threshold, it will read infinite (or very high) resistance.
Feel free to PM me if there's any testing you'd like me to do with voltage levels, etc.
