First picture is of the 2 igniter boxes that send power to the coils for spark. Not there.
Second pic is regulator that is plugged into the main wiring harness, where the juice from the 3 yellow wires ends up eventually. Not there. It's at the plug-in for that group of wires.
Third is of the generator brushes. Not exactly there.
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Trace the wires coming out of that left side cover (see my pic 1), and they will eventually plug into the main wiring harness regulator (my pic 2), unplug it and check those wires.
Before you put the cover back on check the condition of the 2 slip rings - ideally, they should be copper colored. (my pic 3). If they are dark, clean them with a pencil eraser. Don't use sandpaper or anything rough - that will wear out the brushes.
Here is how most charging systems work. A magnet on the end of the crank (the rotor) spins very closely around 3 sets of stationary wire windings (the stator) bolted to the cover or the engine case. This creates AC voltage (the yellow wires) that end up at the regulator, which turns it into DC to charge the battery.
What look like thin, bare copper wires are actually coated for insulation, so they do not make contact with adjacent wires. By checking for continuity between each pair of yellow wires at the plug (left and middle, right and middle, and left and right), you are checking there is no open circuit.
By checking each yellow wire, at the plug, to ground (like the cover when it's bolted down, or anywhere on the engine) you're checking for a short. Hopefully the stator checks out okay.
Here's where things get a little complicated. All of Honda's earlier singles and twins, and on almost everything made after 1985, the rotors used permanent magnets. On these SOHC CB650s the rotors are electromagnets, meaning they have no magnetic power until electricity is put through them.
This is done through the brushes rubbing on the slip rings, which attach to the 2 ends of the rotor windings. One brush gets 12 volts from the battery (via the regulator), the other brush goes to ground - and now it's a spinning magnet.
So the brushes have to be long enough to be making contact against clean slip rings, and there has to be continuity (about 5-7 ohms resistance) between the 2 slip rings of the electromagnet.
The regulator monitors battery voltage, and prevents it from taking too much voltage, say around 14 volts. When it gets too high, too long, rather than boil the battery, it cuts the voltage to the slip ring, so it is no longer a magnet.
CB650s with these brushes (same as on all '79-'83 DOHC inline fours and the CBX) all suffered from this good design in theory, not so much in actual practice.
Hope this helps.
