Thanks Dave I did not want to run to the expense of the powerdynamo system. Rowolf many thanks unfortunately through no fault of yours the link you attached part of the wiring diagram was missing
My train of thought started after seeing the attached on utube. see link
http://www.youtube.com/watch?v=ljDFwVgvELI Also on utube is a conversion of a Suzuki 100 but that's in Spanish so that rules me out!!!
The bike I want to convert is a TS250, I can purchase a voltage regulator from Paul Geoff in the uk as used on BSA Triumphs etc but its the wiring in of the regulator into the MZ circuit and possibly changing around the wiring on the alternator that I'm not sure of. So any help ideas will be most welcome.