There is any connection with the regulator a nd the sparks ? in my mind no, or at least the problem will affect both sparks . do the above sound good for you?

Check the coil and the wiring to the coil, maybe you have a bad pickup or a bad igniter box?
So many things to check!
Walk away have a nice coffee then come back
Paul

Hi Paul you gave me the best option and i improoved it. i walk away and had same beers and this mornig i just checked the spark plug, i switched the front Spark plug with the rear spark plug, realizing the problem was on the front spark plug, not in the coil or ignition related stuff.
Then i replaced the plugs with a couple of old Champion L-4g and the bike finally fired up and run good.

Awesome!!
I will come and have a beer with you
Paul

Hi Paul yes would be great
Filippo