I have this spare connector on my bike (UK) but I don't think the RX3 in the USA has it.
A while back I did a little digging to try and find out its purpose .
http://www.chinariders.net/showthrea...038#post184038
I think it was to power a fuel shut-off solenoid, this would then be connected to a " tip-over " sensor via the ECU.
For some reason Zongshen decided not to fit this system.
This was my best guess after looking at the circuit diagram.