I Need help anyone???

Hello everyone I need help with Norton Commando 850 1975, So i bought my norton one year ago and it was running fine till few months later start to give me a problem; my head light went off and I lost power so I tough that may be the Rotor and Stator and that the bulb, so I replace the bulb and still the same no light, so this is the work done in the bike:
Replace Wiring Harness: Head light harness, Ignition Harness, Main Harness, Rear Harness, New Stator and rotor, New battery, New Coils, New Voltage Regulator(PoDtroinics) which with this one you not need the Zener Diodes, So I went for a ride and I lost power again!! Any one help?

Ugh on electric gremlins and luck of the draw to get me on rare moonshine high comfortable numb but who is in contact with a number non forum guys with weird issues all over the place, so first thing that comes to my mind is faulty stator eating up batteries. Yes remove or disconnect Zenor and leave for looks only. Blue can should not matter here on or removed. 400-ish volts should be measured going into the Podtronics and 14-ish coming out. Disconnect all but ignition then add back lights and brake to see if that matters or not. Sometimes just looking at night tugging and jerking around can reveal a flash of insight. I've had some definite carb related miss fire throttle rpm issues to dead system that was solved under tail light lens for instance. So just how much a man are you to figure out such a lawn mower simple machine that has made me a whimpering infantile t00 many times. Do check and replace the fuse just in case regardless of how it looks as caught me out at least 3x's so far.

After the bike stopped, what was the charge in the battery?
If down either not charging or a ground draining it too slow to blow fuse.
What type of ignition do you have, points or electronic?
If electronic I'd check all wires in and out.
If points I'd wonder if capacitor pack at coils is bad.
Single or duel carbs?
Did you confirm fuel flow from petcocks?
If single I'd do a good clean out, but if duel probably not a carb problem.

If you jiggle the wires to the ignition switch, or the switch itself, does the power come back ?

its not unknown for the switch to wear out inside, so contact is lost or becomes dodgy or intermittent.

Hi, Welcome! Troubleshooting, rather than changing parts would be preferred for cost/time/sanity reasons. Do you have a workshop manual? Find the schematic, begin at the battery. Check for voltage, then the next device (ignition switch on my older bike), then so on down the line. Wiring harness is frequently replaced, thought to be the root of all evil. Unless it's had many poor repairs, then it's usually better to repair it as needed, if at all.
These female bullet connectors have the lion's share of responsibility for electrical gremlins, probably a lot of the "Prince of Darkness" jazz too.

Check that kill switch!

Have you taken apart the fuse holder looking for oxidation around contacts ? Have you tried a new ignition switch (non -Lucas)? As suggested the kill switch could be working a little too well. And yes the brittle harness connectors will give you grief for life ,in winter you could replace them all with modern ones.

I think there's a earth in headlight cowl bullet connector that pushes into headlight housing that wouldn't hav dislodged would it I'm no expert on electrics but could be worth a look good luck