suzuki gs1000s charging - or rather lack of charging

[met999]

gday all....i have a 1980 gs1000st and i have recently had a flat battery issue after riding this bike, on two occasions.
connecting it up to a voltmeter confirms that it is not charging as the number shown in volts 12.1 volt does not change with a twist of the throttle.....and that's my limit of "expertise" has now reached.
question is: how do i know whether its a stator or a regulator problem and how do i test one or the other or both, for function?

[Brendan W]

Disconnect the three wires from the stator to the R/R. Run the motor at about 5000rpm and check the AC voltage between each pair of stator wires. You should be getting 70V + on each pair ideally.