you need a good battery it a must buy good quality , especially with newer motorcycles as they have no back up kick start , which is a step backwards in my opinion .
common problems Yamaha YBR 125 flat - weak battery
- Battery faulty or worn out , replace battery after checking voltage levels , fluid levels and specific gravity .
- poor terminal contacts ( happens a lot )
-excessive load ( remove some of them lights , stereos whatever )
-faulty ignition switch
-alternator stator coil failure ( test for open or shorted coils )
-faulty wiring ie short on loom or loose connections (check wiring and contact clean all connector blocks )
- faulty reg rectifier
-wrong battery size