Replacement alternator for your Royal Enfield.
Information regarding converting from a 3 wire to a 4 wire alternator:
Both 3 wire and 4 wire bikes have only two wired coming into the R/R. They bring AC current from the alternator to the R/R unit. The other two wires are DC plus and minus. Thus the AC alternator brings juice to the R/R which turns it into DC so it can charge the battery.. On the 3 wire unit two of the wires (violet and green) are twisted together to make one. The white is connected. by itself to the other lead going into the R/R unit. The 4 wire has two wires that bring AC from the alternator to the R/R unit/. The other two are used to power the headlight. The headlight is AC as only RE could do.
So we don't give a damn about the headlight on a 3 wire (pre-99 1/2) bike. The lights run off of the battery on DC like a normal human being would design them.
You should have 2 violets and two black coming from the 4 wire. If not that then maybe 2 violet and 2 of whatever colors they had the most of that day. The two violets go. into one of the incoming wires of the R/R unit and the other two go into the other wire. So you are taking 4 wires and pairing them up.