Culprit giving Voltage Regulator Failure reading - check for bad/broken wiring

[workace]

 I had two occasions of battery being drained, on a brand new battery. First one I discovered after riding for about 1.5 hours the day before and the bike sat overnight outside and had the steering locked, I took the battery to the store and they checked it (11 volts) plus charged it. I checked the system for charging and everything looked OK so I attributed the situation to maybe I left it in park with the tail light on.
     The second one was after I had traveled out about 45 miles to Geneva On The Lake in Ohio (motorcyclist heaven), rode around town and after 2 hours total time riding around I stopped at a MacDonalds near there before heading home. Came out and the battery would not turn over the engine, fortunately a past motorcycle rider had jumper cables in his wife's car and got me started.
     On the way home I went to the battery store again (which is about 5 miles from where I live) and took out the battery and it tested at 10.75 volts.  They put it on a slow charge (24 hrs) and since they do not test the batteries on vehicle nor the charging system, they were nice to lend me a battery to get home. As I drove past an AutoZone, I remembered that they do on vehicle battery and charging system checking at no charge. They were gracious to check it and the battery read good (less than a 1/8th of mile driven from battery store), then they tested the charging system and the diodes passed but the regulator failed.
     I was able to get home with no problem. After researching sources for a newRECTIFIER/REGULATOR ASSEMBLY last evening and today, I embarked on taking the bike apart to get to the RECTIFIER/REGULATOR ASSEMBLY and see what damage was there.
     Upon removing the outside cover on the right side I took a picture of the area (attached) and then after I removed the screw and moved the IGNITOR UNIT ASSY in preparation to remove it, I noticed that the yellow wire with black stripe was cut right through and also the grey wire covering was broken through (picture attached). Since no one has serviced this bike but myself for many years, I can only attribute that to mice.
      I still went ahead and took out the RECTIFIER/REGULATOR ASSEMBLY to check the connectors and the back of the unit. It was in pristine shape after 31 years of ownership. 
      I soldered the yellow wire together, used shrink tubing and electrical tape to cover it, then I also covered the grey wire. I put everything together and installed the battery, started the engine and did the Ohm Meter test set at 20 Volts DC and to my pleasure I was getting 12.87 Volts and as I revved up the engine the voltage went up over 13.0 volts.
      Since it was after 9:00 p.m. today when I was doing the test I did not go any higher in the RPM. Tomorrow will be the ultimate test as I crank the engine up and see if the Voltage will increase and remain in the operating range.     

[Rikugun]

I don't think repairing the cut wire will correct your problem and if it does seem to, it's just coincidence. The wire in question is from the tachometer to the TCI and is responsible for the rev limiting feature. The feature is purportedly known for failing with the unfortunate consequence of causing running issues. It was likely disabled (at the dealer?) by snipping the yel/black wire at the TCI and perhaps got into the grey wire's insulation inadvertently with the tips of the diagonal cutter jaws.

EDIT: To your 2 instances of battery being drained. The first seems like a good guess where you suggest the ignition may have been left in the park position. The second instance may simply have been the electrical demands outstrip your charging system's ability to keep up. I suppose it could also be the rectifier leaking despite AutoZone's findings. Either way, 12.87 and 13.0 are not good voltage readings in my opinion. BTW, while melted R/R connectors and corroded connections may indicate failure, a pristine looking R/R in no way guarantees it's health.

If you had nominally 14 volts at the battery at idle or at least that at moderate RPMs, I'd feel a lot better about the charging systems overall health. Have you checked the stators AC output? Do all test with the bike and components at operating temperature for more realistic results.

[The Prophet of Doom]

Either way, 12.87 and 13.0 are not good voltage readings in my opinion.

Yes, way too low.

You can check out your system using the Electrosport fault finding chart

[workace]

You are right, it was just a coincidence. Upon finding the Manual I realized that the yellow/black stripe wire was for the tach (interestingly the tach never stopped working, it must have been connected by a strand or two and when I released the IC it must have finished breaking). I should be getting 14.5V +/- 5.0V per the manual. I took every connector apart and cleaned them. Checked the stator's white leads continuity to the engine block and one showed OL and two showed 0.00.
Next step is to test the AC Voltage and if it does not register 50V then it is time for disassembly, unless I have missed a step. Please advise if anything else I should check before I start to take to bike apart.
Thank you for your input. Will keep posting on progress 

[QBS]

The tach gets it's signal from a grey wire attached to one of the low tension feeds to the spark coils.   

[fret not]

All three white wires should read the same.  Have you followed the procedure for checking the stator? and the RR unit?  They are available on the HOME page under the Technical section.

[Rikugun]

It sounds like one of the 3 stator windings may have spit the bit. Follow-up your ohm check with a dynamic AC voltage test when the engine is hot. If you don't get 3 readings of 50ish volts, it's time for a new one. If after replacing the stator you still don't get 14 at the battery while running, the R/R has likely failed as well.

[fret not]

This reminds me of a sign inside a sideshow at the circus, "SEE THE EGRESS".  If you go through that door you find yourself outside the circus, and must pay to get in again.