You need a coil for a CDI ignition system (actually 2 coils). The easy way to make a toroid coil is to use a 2 part coil form with a plastic bobbin. These are commonly used by ham radio builders. The coil cores are very cheap, and very easy to wind. Amidon Associates is a common supplier. Check on line to see if they still sell them. If not, there are other companies that supply them.