Tuono´s (and Milles) need the battery reasonably well charged. Once the voltage drops below certain level it will still turn engine but voltage will drop too low for the ignition system to generate a spark. Also onboard electrics drain battery even with ignition off... which is why all forums advise users to keep bike on Optimate type charger when not used for 3 or more days...
These are great bikes, very reliable... but just need understanding... as above.