I was staring this same problem in the face the other night.
Fortunately my points looked good, so i don't have to mess with them just now. However, i am almost certain that i (you) will have to go to the auto store and rent a puller (a tiny one) for this particular job. I don't have a manual for the Minarelli, but it looks like the only way. I soft tapped the "flywheel" with a hammer and a rag for a while and didn't get a budge (implies good construction,!). If you can't get the nut off the end, stick a drill bit in one of the holes in the flywheel and butt a hammer or something against it for resistance. Go soft, though, as the brass is soft. Good luck. Post any good tips on this particular maneuver, as i will problably need it in the near future. P.S. am i mistaken or is there also a small, thin ring of some kind on the shaft that has to be dealt with?