Charging issue
 

I just got a 2000 Gz 250 for my wife as a starter bike. Brought it home and found out that the battery discharges while riding. I charged up the battery, tested charging and it is not charging. Tested the stator as per guidelines, it is out putting over 65 AC volts on all phases. Output from rectifier was 8 volts. I replaced the rectifier and still no charge to the battery. Disconnected the rectifier battery connection and tested voltage there, it show 13.5 volts. However, voltage at same plug when connected drops to 11.5. I’m not sure what could be causing the charging voltage to drop below the required voltage when the rectifier is plugged back in. The bike stalls immediately if the negative terminal is disconnected from battery. Any help is appreciated.

Have you tested the battery itself? Try charging it at a low current (0.75A is recommended) then let it sit for half an hour and then check voltage. Let us know what the voltage is. Bad batteries are often the cause of problems with the GZ, so lets get that out of the way first. BTW, don't ever use a car battery charger. The current is way too high, and will fry your bike battery. A bike charger is usuallycheap. Mine cost €15 (less than $20)

Bought a new battery and charged as instructed. The voltage is 13.05.
When the bike is started I can’t get any more then 12.3 even with full throttle. As it runs it loses voltage. However, again if I disconnect the two wire plug from the rectifier and back probe it at the regulator side it is producing 14.5 volts. As soon as I plug it back into the bike it drops back down to 12.3 and declines. Should the bike stay Running if the battery is takin out of the circuit? I’m trying to eliminate possibilities.
Also, I over laid positive and negative wires from the regulator to the battery to eliminate any possible corroded wires. Same result. Could it be a week stator?

Update
 

I disconnected all the lights and started the bike. Tested the battery before starting. It showed 12.87 volts. Ran the bike at high rpm (no tach) lost .05 volts within a minute. The rectifier and battery are new.

Sunds like stator.