Thanks for the clarification. I'll pick up new main jets, needle jets, idle jets, and move the jet needles up one clip to match the R75/6 specs.
I was still getting a KA-THUNK when pressing the starter button and no spark when kicking, so I stared at the wiring diagrams for a few hours, tested the ignition coils with a multimeter, replaced the brushes and bushings on the starter, and generally cleaned the shit out of the the housing and all electrical connections. Still nothing but a ka-thunk. Then yesterday I woke up and for some reason my first thought was "Am I hooking the cable from the starter solenoid to the positive or negative battery terminal?" I went out to the workshop in my pajamas and, sure enough, I was hooking it up to the negative terminal. God only knows why. I switched it to positive and:
Also getting a nice spark, which means I can start it up in the near future. That being the case, I started reading engine break-in threads for Nikasil cylinders. Jesus, I had no idea how important the first few minutes after first start-up would be. My initial plan of just trying to get it to start are now officially abandoned. I'm going to try to start it up right the first time, which means immediately taking it for a ride, apparently.
Remaining issues before it's road-worthy:
1. Gearbox is leaking oil from the back cover. I'm going to try conventional 80w90 to see if it helps. It currently has full synthetic.
2. Half the bulbs in the instrument panel are burned out, so an all-new replacement set of LEDs from superbrightleds.com are on the way.
3. Find and fix the fuel line leak.
4. The tire is rubbing against the swingarm.