Lets play where does it go

On my kz900 where does the small black/yellow wire that comes off the neg battery terminal go to? I have a few female connections it will reach but the recto/reg is a one piece aftermarket unit so there are probably some extras.

you would assume the ground wire goes to nothing but ground wires. esp if its off the battery. if everything is working fine i wouldnt worry about it.

The regulator ground connects to a ground wire coming off the stator on a KZ900 I think... the extra ground you are seeing... check to see if your rear brake light works. The brakelight is fed a hot through the BLUE circuit on the KZ900 and the other wire coming off the mechanical rear brake light switch is the ground. I am thinking this is what should be connected to the ground next to your main ground which should connect to the engine cases just behind the switch and above the kicker mechanism.