I mentioned this in passing early on, but one thing I am planning on doing is building a crossover shifter arrangement for a modern standard right-brake/left-shift arrangement. (I’m old enough that my neural net and premotor cortex don’t adapt as easily.) I could find a late (’75-on) Bultaco lower end with the shift shaft exiting on both sides of the cases but, the “left side” shaft actually exits the cases directly inboard of the drive chain:
As you can see, any sort of rearsets would still require some sort of goofy linkage around the chain run anyway. Besides, I already have earlier, right-shift-only cases and transmission parts. And finally, if I set it up with a crossover shaft, then I can put any Bultaco motor I want in it later, on the off chance the chassis ends up being something more than pure garbage when finished.
Sooo… I’m currently thinking about how to incorporate a crossover shaft into that lower mounting location for the engine plates. The rubber mounts might complicate that, since they dictate the maximum diameter. For refernce, when I was at the British National Motorcycle Museum about five years ago, I took some photos of how a couple of later British bikes did the crossover thing:
