Good point. Thanks for bringing that up. Brain schism. About 10 years ago, i built an ignition using and arduino mini to map ignition timing. That approach could be done here pretty easily with an arduino intercepting and modifying timing, and letting the CDI box provide the spark. (I still have my notes from that exercise). I had forgotten about the timing advance reduction at high speed.D'oh!
I didn't spin it up too fast (maybe 5 k) and the two data points i had (small speed/high speed) were about the same.
OR, instead of the arduino, the easier thing to do would be to buy a PW80 CDI (
https://www.ebay.com/itm/IGNITION-CO...oAAOSwAtlcqx4s), figure its wiring, and then run it to check its spark advance curve (all the way to higher speeds). For $16, i could do that experiment, too. Maybe that will be this weekend's project.
Thanks for bringing me back to reality. it might be worth $20 to have a spare/good CDI to check if you have ignition issues.