yes electronics can go out with no freaking warning.
to test the stator properly you'll need a DVA adapter and jumper wires...but you can do preliminary tests with just a multimeter.
ditto for power packs you can do preliminary OHM tests
but to do voltage tests you'll need the dva adapter (that fits into your multimeter)
Stator - most have two windings
1) for the battery - usually two yellow wires that go to the voltage regulator
2) for the hi-volts for the power packs - usually two brown wires per pack...
with multimeter set to CONTINUITY, there should be NO continuity from either yellow wire (disconnected from distribution strip) to ground.
Ditto for either brown wire with the two-wire plug disconnected
with multimer set to ohm measure the ohm between the two yellow wires and between the two brown wires and compare those to expected OHM on the internet....CDI electronics has the numbers and the DVA adapter and jumper wires.
do an OHM test on each coil and each plug wire too. touch the two probes together too to make sure it reads 0 first...if not note the number say .6.....then if testing the coils ohm and it says .56, subtract the .6 to get your actual reading to be .50 ohms
If this has the optical trigger system, then that to could be the issue....I don't have one of those so can't tell you how to test that....from what I understand THAT is NOT uncommon to be the source of engine not firing right...and that TOO just goes out willy nilly.
let us know the results of the tests