the 12 volt lighting charge circuit is separate to the ignition. you will have to study the manual to determine if you going to be able run the ignition side of things into a CDI and then a coil, because as standard its a all in one unit. I would not go using yamaha components, stick with suzuki as they use the same colour wires across the board. your also going to need to determine what sort of ignition it is. To me it looks like it could be a low voltage DC system which only uses a pulse from the stator and the power comes from the battery, in that case that will likely prevent you fitting any late 70's/early 80's RM CDI and coil.
i would be getting the full TS125ERZ set up first, coil, flywheel,stator,cdi.
another thing, what if the ER stator only has 2 ignition wires comming out of it, but yet your YZ 80 or RM125 CDI unit has 5 or 6 input wires for example. Then what are you going to do? see what i mean?
Just looking at the wiring in the haynes book now and yes it appears the ignition would be a DC system with only pulse comming from the stator and power coming from the battery, the pulse comes from the stator on the black/red wire an then there is the black white wire for earth. 2 yellow wires come from the light coils connected in series which go into a single phase regulator rectifier
there is one wire only going into the CDI/ignition coil unit which is the black/red wire. This tells me any HV ignition system components wont be compatible or easily fitted.
this also means that if your battery packs up you cant start your bike unless you run a elecrolyitc capacitor in parralel with the battery for emergency starting. Many old british bikes had this set up which used a blue Lucas 2MC capacitor.
