Remove the frame ground from the AC circuit and everything should work fine. I'm not sure what style of headlight you've got but make sure the negative side of the bulb isn't connected to the housing and therefore grounded to the frame. One last thing, all AC regulators have only 2 wires comming out of them, your drawing shows the AC reg with 4 wires (2 from the stator and 2 going to the light). If your regulator has 4 wires than it's a DC regulator. A typical DC regulator will have 2 yellow wires and 1 black and 1 red wire and a typical AC reg will have one brown and one yellow wire only. Or is this just a typo in the drawing so to speak?
XR650R Plated Supermoto
XR628R Plated and highly modified
CR500R Still rips after all these beers
RZ350L Kenny Roberts Special
KTM300EXC Plated & So cool