Motorcycle Repair: yamaha tenere xtz 660 dying battery, tenere xtz 660, electrical problem

Question
Hi . I have a 1998 yamaha tenere xtz 660 with 70000kms on the clock and has been always professionally serviced,
I bought it a few weeks ago and one day the battery went dead, i jumped started it and after a few days it went dead again. So i bought a new one and it only lasted about a week before also going dead. I asked a local mechanic about it and he advised that the charger rectifier needs replacement as apparently its a common problem with these bikes. I put a new charger rectifier in and fully charged the battery overnight. it turned on first go but this time it lasted about 2 weeks. i jump started it and again went dead after 1 week. the bike is ridden almost everyday. I think its an electrical problem and just wanted to know if you have a solution for this problem?
many thanks  

Answer
definitely sounds like a charging problem at night crank it ride it if yur headlight are dim then when u throttle up they go bright yur ok if they dint charging problem i have seen many defective rectifires just to mlet you know also while bike is running check charging system ast the battery.

mitch