Giantco Hunter 125 voltage issue

After purchasing a 60 plate with 7k I seem to be having an issue with thevoltage on the bike, it uses the 156fmi lump.

Despite changing the battery, the cdi unit, the rectifier and the stator I can't seem to get more than just under 12 volts meaning that with a bit of use the battery runs flat.

Having changed all the parts above I'm a bit lost as to what to do next with it as I thought that changing these bits would have sorted the problem but alas no, so if anyone could give me a suggestion what to try next it would be hugely appreciated as I'm a bit stuck.

http://www.mychinamoto.com/forums/showthread.php?5301 had similar story.
Why changing CDI? It's powered by another AC source directly.
You can't solve the ??? by just guessing (changing parts from here & there). What's the reading of wiring countinuty etc ... In extreme case the rotor may de-magnetize.
http://www.sanxin.com.cn/Exhibit/exhview.asp?pid=53 The reg works when "control (middle) to s/w (ON)" are connected!!! If something breaks btw them :naughty:
How to test reg: http://www.sanxin.com.cn/info5/index.asp?id=6
Self-contain test system (By-passing ALL those time cousming wiring !!! ) http://www.motorfans.com.cn/bbs/t_125842_1.htm