What interests me is how the spark is generated, but also, as the OP asked, do these small engines have an advance
curve? There is a lot of hearsay out there, but little first-hand data that I have found. I have heard numerous times
that some of these small 2-strokes had "retarded ignition timing", which I doubted. My data shows, mostly as predicted,
that all of my sample engines have advanced timing, some with a continuous curve.
Without access inside one of these modules, we can't reverse-engineer the circuit, or place an oscilloscope probe
on anything but the HT lead. I am still in the process of non-destructive de-potting of a Husky 3-pole module, but
it has been slow. So far, I can see two separate coils wound around one pole, and a pair of poles. I soak it
in lacquer thinner overnight, which allows me to scrape off about a half mm of epoxy at a time.
I tried for years to find aftermarket substitutes for OEM igniters for one-cyl ATVs with dead ignitions. Of course,
these required a battery and a fairly hi voltage pulse off the engine's stator.
A magneto/flywheel driven EI/CDI is energy rectified and then power dumped to make spark is key concept in my book. I spent over 2 decade in electronics repair. You might find that rather than real "epoxy" these items are encapsulated in electronics "potting". They are quite readily depotted by scraping if heated with a heat gun to reduce its strength. I did tons of "depotting" including my dead 330 EI. I will admit to not being overly careful on that item and I might even continue from where the pix showed. I'm almost positive the coarse winding is the powering coil that is diode rectified into the big? cap...then the Capacitive Discharge Ignition is dumped/powered into the primary which will energize the fine wire high voltage secondary. Any advance (actually reduced delay) circuitry will likely be fairly simple. Sort of along the lines of a simple electronic tach circuit that alters the bias on the trigger of the (probably)SCR...based on RPM..