Hi Randy,
Take a look at these threads:
Voltage regulator still bothersome (I think) - #3 by clivejer, XK120 Dynamo / Generator, Voltage Regulator problem - #13 by clivejer
The Lucas document takes you through all the steps to discover where the problem lies. If it is an old regulator then it will probably be dirty contacts, which can be cleaned, or a bad earth connection somewhere.
Regards,
Clive.