Hi Fabio,
It is a 1 cylinder engine, i assume.
If you gonna feed it with HHO, then please do not forget the ignition system.
I do not mean the timing specifically, but i talk about the waist spark.
A single cylinder also fires a spark at the exit stroke.
During that stroke, the engine also opens the inlet valve a little bit for getting a better flow.
You can imaging what happens......
Thats the resean why my left ear is a bit deaf.
.....
cheers