You'll need a small puller to remove the magneto sprocket.
The Magdyno itself has to be removed with the platform attached. (It's held on by four staked countersunk screws. Its then necessary to loosen the rear engine plate bolts / studs and remove the top one, together with the short locking bolt and plate.
Hopefully, the bolts were positioned correctly with the nuts at the primary chain case side, otherwise the primary drive (pinion, chain and clutch) and chain case needs to be removed.