Good news is the issue is predictable and repeatable. Now just to wonder why.
Ran 15 minute idle test - puuuurrrrfect. Cut it off, put on the helmet start and stall. When temps hit 3/4, choke and puke.
Here's what happens
With all the talk about it, do you think the reg/rect is overheating? I haven't looked at it but if it's a part that's easily swapped you can borrow mine to see if it fixes the problem.