Don't disconnect or reconnect the stator plug when the bike is running, it can (and will) fry the stator.
To check stator rotor output:
1) disconnect the stator plug
2) start bike
3) set multi-meter to VAC
4) read across the stator plug (one probe in each hole)
5) have someone rev the bike up to 2000-3000 RPM
6) stator/rotor output should be 16-20 VAC per 1000 RPM
To check for a shorted or grounded stator:
1) set multi-meter to "ohms"
2) read across the stator plug
3) resistance should be 0.2-0.3 ohms
4) now check each stator pin to ground
5) should have no continuity
6) kill engine
7) reconnect stator plug
To check voltage regulator function:
1) set multi-meter to VDC
2) check battery voltage...12.5-13.0 VDC
(if the battery isn't fully charged, this test is useless)
3) start bike
4) hold the red lead of the multi-meter to the positive post of the battery and the black lead to the negative post.
5) increase engine RPM to at least 2000 RPM
6) multi-meter will show regulator charging rate which should be 14.2-14.6 VDC. A brand new fully charged battery will sometimes only indicate 14.0 VDC; anything above 14.6 VDC is cooking the battery.
Did the stator go bad first or the regulator?
A bad stator will take out a regulator and a dead short will ruin both.
A bad or intermittent ground on the regulator is never a good idea either.