have you tried to directly wire the starter to a battery? If you have the starter off the engine when you try this, be sure to secure the starter. It will try to jump off a workbench. Broken motor brushes used to be a problem with the old Leopard starters.
I’ve also had battery chargers fail. A new, fully charged battery should read at least 12.5 volts.
LAD Specialties customer / tony kart / rotax / kt100