The Zephyr Zone

Put a toiletpaper on top of the carb and you will know if it's the carb itself or the fuel supply above it?

Owning a 750 myself...
So are you looking for a Alternator or a regulator?

I've had this issue multiple times until I figured it were rust particles coming from the inside of the fuel tank.
Long story short, I fixed the tank and I had to replace the petcock, it didn't shut fully always, also caused by leftover rust particles. Problem was gone.

Just wondering if there's any update or did you cancel this project now...?

I would first investigate if this is fuel related or electrical. You replaced much within those carbs so can be anything in there. Does (fresh) fuel reach all carbs? There's a drain screw in the carb bowls, put the petcock on prime and loosen each of these screws one by one (and close it afterwards)...

fresh fuel used?

O no, that really s*cks! I can almost feel your frustration

Hope you will find a decent sollution and soon...

Before any (electrical) welding is done, make sure all electronic components are disconnected (also from earth), disconnect/remove the battery and perhaps disconnect your new headlight cabling...

Looks great and I do hope you can now enjoy your hard work. Start riding now, it's summer, all other stuff can be done in winter time

I would suggest to check by circuit. E.g. your starter circuit is one and your headlight is another. With the battery connected only use a voltmeter to measure if the destination gets a voltage. You can also follow a circuit with an Ohm meter (measure resistance) but do disconnect the battery on tha...