where can I get a wiring diagram for a 1916 model
There really is no wiring diagram that I know of for a 1916 which would have magneto headlamps. You can wire them either with a switch or so they are on all the time. If you are running a switch, you will have a wire running from the mag post to the switch, from the switch to the left headlamp. Run another wire from the other terminal on the left headlamp to the right headlamp, then run another wire from the other terminal on the right headlamp to a ground.