84 RM125 no spark

I would guess that the stator is the culprit here. But before you spend any money i would remove all the electrical connections on the bike and clean them real good (this includes sparplug caps and kill switch wires). Look for any wires that may have grounded out on the frame. You should also inspect the magnets on the ignition rotor, i had a busted one on my 80 and it took me forever to figure out why it stopped runnin. I hope you dont have to spend much dough! Good luck!

To determined if either of your source or pickup coils are dicked, do a resistance test on the pairs of wires from your magneto at the connector to the CDI. If they are out, you will need to get the dodgy coil rewound, then she'll haul arse again