I would like to get hold of a faulty set of pickup coils to tear apart with a view to making copies but no one this side of the Atlantic has anything, I really don't want to destroy a good set.
I've wound guitar pickups in the past, the principle is pretty much the same except on a bike they would need to be water proof, heat proof and vibration proof, potted in resin instead of wax, making bobbins and housings isn't a problem for someone with a 3D printer.
I'm now thinking towards using hall effect devices instead of pickup coils, with an interface box which converts the Hall Effect trigger signal to something the TCI understands.
The downsides to that are that the Hall Effect devices need a power source, that would probably involve fitting an extra wire down to the pickup, plus the interface box would be an extra thing which can go wrong at the roadside.
Me and my son, (who is much more clever than me with electronics), are currently working on a direct copy of the TCI, most of the compononts are easily availible but there are some unidentified diodes on the board so it's going to take some measuring, swapping and testing to find equivilents for them.
I'm currently working on building a test rig which will have an inner spinning disc with an embedded magnet which is driven by a brushless model plane motor with variable speed control, an outer stator disk marked with, (virtual), TDC and degrees of advance, using real coils and spark plugs I will be able to to use a strobe to look at and plot the timing advance curve from the workbench.
So yes, there are people out here doing stuff, it keeps the brain from going the same way as the creaking bones.
Neil