Amazing you should mention this.
I've never really liked the design of our mechanical advance. Tiny flyweight nubs fitted into narrow slots of the slotted disc, trying to precision control 12.5° of rotation over a short radius, all in a demanding/hot/vibrating environment.
I've rewelded mine to close-up those sloppy clearances, but it won't last very long.
Then, there's the issue of exploding aftermarket advance units.
Been contemplating building something like this:
Note how the flyweights control the central shaft over a much longer torque arm, loads spread over a larger area.
Also note how the return springs keep the flyweight fingers in constant contact with the central shaft's arms, eliminating timing 'jitter'.
Another 'blue sky' project...
