New Stator, Rectifier and battery, but voltages only slightly goes up????

[Volgen83]

im reading a voltage off the battery and when i start the bike the voltage starts to drop, slowly, as i increases revs the voltage goes up bu no where near what it should be.

i have checked the output at the rectifier and its bang on but there's an issue between the rectifier and the battery (just a guess) i have checked all the wiring and connections, can't see anything obvious.
i have a spare harness (ebay) and may butcher the plug to the rectifier from it and hope i have enough spare cable on it to run direct to the battery, see if its the plug.