It does look like your PO did a methodical job on the wiring. Clearly labeled everything. As you said, too bad he didn't give you a list of what the labels mean.
I recommend to people that they match the new wires to the old by color. That makes troubleshooting easier. Most know that a blue wire is lighting, brown is power to most of the bike, and so on. If someone rewires with different colors they ask what the brown wire goes to and most replies are to the factory color scheme.
In your case this doesn't help much. What I can suggest is to start at the battery positive and trace the wires and make a diagram of where each wire goes. With your labels that shouldn't be hard.
You might want to write each system down separately. As in the charging system as one diagram, the ignition as one, the lighting as one. This might help with troubleshooting.
On your reg/rec I agree, it looks to be a combined unit. The description of the way it's wired is right for the 80 up bikes. The ones that came with a combo reg/rec. Your bike being a 78 or79, then it came with the separate reg and rec. They are wired differently at the brushes. The 70-79 bikes used a grounded brush and the green wire sent power from the reg. The 80 up used a brown wire to power one brush and this power went back to the reg/rec where it controlled the ground.
The earely brushes had one brush with a long mount strap that went from one screw up over the brush down to a second screw and went sideways to a third screw. The brush grounded to the stator housing through these three screws as well as on the black wire back to the harness.
The later brushes mounted the same. both just a short strap that came from under a screw and up over the brush.
Look under the alternator cover, the round one on the left side. Look at the brushes. See if they both use short straps or one has a long strap.
I'll post pics.
The early can be used with a late reg/rec by replacing the three steel screws that hold the grounded brush in with three nylon screws and running a brown power wire to the black wire. It's describe in more clarity in the threads describing the three screw mod.
These pics are the early brushes, holders and a pic of the early stator. It shows which three screws get changed. You can see that the wires that come out of the stator both hook in close to where the come out. The green to the lower screw, the black to the upper screw.
Leo
