Check your coil windings with a multimeter on the resistance setting across the 3 windings, if they are all within a couple of ohms of each other your probably OK, I think they should be about 50 off the top of my head, if one is miles different take off the cover and check if it has burnt out
Good luck!

1-2 ohms resistance and 50 volts AC when engine running at 5000 rpm measured between pairs of yellow wires, with rect/reg disconnected. Infinite resistance between yellow wires and chassis with rect/reg disconnected.

What he said :-) my wiring book is in the garage . . .