May be you can see, whether the Charging is reverse. Means, Instead of Charging the battery sometime due to malfunctioning, the power is used appropriately. Therefore whn u on ur headlight, the power is turned fully to Headlight N Bike gives misfiring.

Hi,
I've not done much work on the Indian Enfield, more on Bsa's/Triumphs etc., However it appears that your charging system may be faulty?
When running can you meter the current to the battery? if 12ish on tickover and up to 13.8/14.5 when revved fine, try popping the side lights on if voltage drops drastically and doesn't improved with increased engine rev's then alternator problem or regulator?
Finally could there be a possible short circuit on the headlight? have you removed the lamp from the surround and looked at the switches rear? make a close inspection of the bulb filliament sometimes they fuse both main and dip beam together causing all sorts of grief.
Hope this helped,
Paul 'W'
Onyer~EDson(:0) {#><U.K.