Questions? Looking for parts? Parts for sale? or just for a chat,
The WD Motorcycle forum
Ian the "Magneto guys" explain it and with downloadable Lucas instructions. https://www.themagnetoguys.co.uk/remagnetising-magnetos Ron
email (option): ronpier@talk21.com
If their work is as good as the web site I think they'd be worth a try.
email (option): pes.sales@btconnect.com