From the symptoms you decscribe it sounds like you have a problem with the starter clucth shoes on the Bravo. They may be installed backwards,
Pull the clutch and looking down into the clutch drum the shoes should be at the 2 and 7 OClock positions. It is easy to install them backwards so they are at 11 and 5 oClock.
I suspect a clutch problems also with the single speed Ciao.
What mods besides the performance muffler have you made to each bike? Upjetting, bigger non stock carb, etc. ?