A quick check of my Kawi service manual spec page reads (next to "alternator rated output"): 24 amps @ 8,000 rpm.
At a conservative 12 volts, this translates into 288 watts.
But most of one's riding time is not spent at 8,000 rpm, obviously.
No data is shown (nor have I ever seen) on what the bike's ignition system requirements are.
My bike is equipped with the standard headlamp, and an upgraded bulb (but still a 55/60 watt rating), and two 35-watt driving lights. All the turn signals have been replaced with amber-colored LEDs. The instrumentation bulbs are still what the factory installed.
At rpm's above say, 2,500, I can still get strong voltmeter readings (14 volts, or so) with the headlamp on high beam, both driving lights turned on, and an LED driving light kit turned on (this kit uses about 1.75 watts of power).
However, your "mileage may vary"....as the saying goes. All this also assumes you are of course still with a factory stator, and regulator/rectifier.
As a more practical answer, I'd say to use the above as a rough guide, and use a voltmeter to test the bike's reserves of power (at different rpm's) as you add additional electrical loads to the bike. A voltmeter will of course tell you when you are overloading the system. As another rough guide, once your voltmeter readings are down below about 12.8 volts, the charging system is probably not doing enough to keep the battery charged.
Since you say you are rebuilding your bike, I would encourage you to go over your bike's electrical system, and clean as many of the electrical connections and contacts as possible (use a spray cleaner for this that does not attack plastics--and with good ventilation!). Make especially sure the engine and battery grounds to the frame are clean (no rust, or factory paint in the point area of contact)--and tight. When reconnecting, use dielectric grease wherever possible to insulate contacts and connections from moisture and corrosion. With the Kawi/Clymer service manual as a guide, test the relevant electrical components (e.g., ignition coils) as appropriate, and replace as necessary.
Inspect the 3 yellow wires which run from the stator to the r/r (left side of bike, behind left side cover). Look at where these wires are connected/soldiered together, and check there for signs of melting/excessive heat. If you see damage there, it may mean it's time to test the output of the stator and/or the r/r. Several very good threads are on this forum to help you with this (use the search function in the links shown above).
After your rebuild is complete, be careful to keep the bike properly covered and/or out of the elements when not in use, to keep corrosion at bay. This bike is a rust farm if not properly sheltered. Keep the fuel tank at (or nearly) full when not in use, to keep rust from forming inside the tank.
Good luck with your rebuild. Let us know how it goes...!