TOPIC:

Hi everyone, newbie question for you.
Bought new regulator rectifier for my bike new one has 5 wires old one only had a 4 wire plug Rick's told me I could convert it to 4 wire.  There are 3 yellow a black and a white  how do I hook that up?

I do not mean to mislead you, but I think the 1980 models came stock with a single phase alternator ( 2 yellow wires from alternator to rectifier) and the new unit is make for a 3 phase alternator (3 yellow wires from the alternator to the rectifier) but it can be used for a single phase system but making use of 2 of the yellow wires. 

 I believe you are correct. So I understand the extra yellow isn’t connect to anything just capped off?  
thanks 

As I understand it yes, but there are others here who are more knowledgeable than I and will most likely chime in on the subject.

3 yellow wires would be for a 3-phase. 2 yellow are single phase.  a 1980 550 could have had either one or the other charging systems.  the diagrams at partzilla differentiate between the two system & I don't think the reg-recs are interchangeable.  but not certain.

You can use any but only 2 yellow wires of the recifier on your wiring harness and capped of the 3rd, it does´t matter.

How many yellow wires are coming out of the generator?

OP needs to list all of the wires.  He's saying his old voltage regulator has a 4-wire plug, but that might just be what's routed thru the connector & there could be an additional wire from the reg-rec (possibly white-red). loudhvx has wiring diagrams on his motorcycle stuff page.

Ok so I've done more reading on this forum... great stuff btw... the wires coming from the stator are putting out 26-29 ac volts at idle and 65 at around 4000 rpm.  The wires also get hot to the touch and the battery shows a discharge.  Once the bike cools off the battery is fully charged again unless you ride until it stalls. 
it is for sure a single phase stator. Not sure what to think.  
thanks for the replies and help