Dan,
Electronic ignition can use a lot of electricity, mine draws 2.5 amps (30 watts, 12 volt). A dynamo like yours will only give about 100 watts when spinning
fast. Running slow, with lights on and a small or old battery will mean you're always running your battery flat and the ignition won't like it. Maybe that's why your father pointed to the dynamo as the problem.
I kept the electronic ignition and fitted an alternator charging system - see Walkernator and others on the forum.
Stick with this forum and you'll find 96 different solutions to every problem
, it's up to you which route to follow.
Good Luck.
H