First of all Welcome to the Forum!
Question? Are you trying to use the OEM R/R that came with the Rukus? Or are you using the 5-wire R/R that came with the donor engine?
If so by looking at the Rukus wiring diagram the single wire you are refering to is going to the stator and looks like to me the Rukus is a 3 phase stator. If so then the OEM R/R will not work with this GY-6 engine because you stator is the standard single phase stator. You could use it if you decided to upgrade to a 11-pole stator.
Now if this is the R/R from the donor scooter then typically the 5th wire goes to the ignition key switch and is black and this wire does one thing anf it reads the voltage on the battery or load and the R/R regulates it's output by the readings on this wire. Typically the 5 pin R/R is;
white or pink = stator AC feed
yellow = stator AC feed
red = dc charge voltage to the battery
green = ground
black = feed to key ignition.
If this is the R/R from the donor scooter and it has a 5th red/white wire if I know the scooter I may be able to find a diagram and see what is goes to?
If you can tell me this then I'll know more what to do.
JR
