Thanks very much most differently only two wires, only getting 48 volts at 4,000 rpm.Most 77-80 KZ650s were single phase w 2 yellow wires. It's possible a 1980 model could be either. Instead of going to the trouble of checking for a broken wire, I guess he could check the voltage regulator to see how many yellow wires it has. 1977-80 KZ650 Stator 21003-1005
In the Clymer manual I did not see charging system specs in the supplement specifically for the 1980 models, so I assume you would use the earlier info...
From the Clymer manual: 78-on >> about 14.5 VDC @ 4,000 rpms.
To test the stator disconnect the yellow wires & test for voltage at the 2 yellow stator wires >> about 75 VAC @ 4,000 rpms (be sure to change the multimeter to VAC).