piaggio fly 125 o6 ?

hi all my piaggio fly has problems the dash light works but the petrol gauge goes on a mad one the battery terminals are tight,ive checket the back of the clocks to see if the connectors are tight which they are,and also when the bike starts the head lamp flickers to please help i dont know wot to do,, when i ride the bike it cuts out and i loose all power the the bike inc the dash lights,,