Welcome. Thank you for choosing Just Answer.
you are not going to find anything of much use on-line unless you get it from Harley and we are prohibited from forwarding HD copyrighted material.
this one is the best one I have found: http://www.smokeriders.com/diagrams/index.php?show=Harley_Davidson/Twins/1973-74_XL__XLCH.gif
that said, if you have specific questions I can answer them for you.
I think with your poor diagram and my instruction we can save your buddy's hair!
if you come across specific issues, let me know and we can address them one at a time.
from the battery to the coil, try to follow this:
batt - to ground, batt + to starter solenoid, long stud.
(solenoid short stud to starter)
there is another wire (red) on the long stud which goes to the "bat" terminal on the regulator.
there are 3 red wires on the "bat" terminal of the regulator.
1 goes to the starter solenoid, as above.
1 goes to the B terminal on the ignition switch.
1 goes to the starter relay.
back to the ignition switch:
a wire from the L terminal goes to the "lighting" breaker, copper stud.
a wire from the I terminal goes to the ignition breaker, copper stud (which is connected to the ACCY breaker by a copper strip).
from the load side (silver terminal) of the ignition breaker is a gray wire that goes to the run/stop (kill) switch.
there are 2 white wires on the kill switch.
one goes over to the start pushbutton, the other goes to the coil.