At the Nationals in Port Augusta I spoke to a few people about the YZ80 ignition I had fitted to my TM125. Sorry it's taken so long but here are some details.
The bike starts better, idles better and makes more power. It hasn't been dynoed but repeated timed runs with both ignitions showed better times with the YZ. The motor also "feels" better and more flexible
The YZ rotor is too small in the taper and a different angle so it needs to be bored. I put the TM rotor in a lathe and set up a finger type dial gauge clamped to the compound slide. I rotated the compound slide and wound it in and out along the bore of the taper and adjusted it till the dial gauge showed less than 0.001". This gave me the correct angle to bore the YZ rotor. Pull the TM rotor out and set up the YZ rotor. I bored it till it only just cleaned up depth of the taper.
The YZ backing plate is smaller than the TM so I made an adaptor ring. I had to file the adjusting slots in the YZ backing plate and make large washers to clamp the stator and adaptor ring in place.
I lapped the rotor to the crank and don't use a key, the keyways don't match anyway. Having the timing mark on the rotor align with the first of the three marks on the stator with the piston at 2.9 degrees BTDC is a fair STARTING point. I advanced and retarded it until it ran the best. Your ideal timing position will vary depending on how your motor is set-up.
Thanks go to Lozza for the YZ ignition and tuning advice.
This is the YZ ignition fitted, please excuse the dirty state of the bike
Showing the difference in dia of the YZ rotor (fitted) and the TM rotor. Those with sharp eyes will notice the TS90MX markings on the original rotor. Same OD as the TM but a smaller taper.
The adaptor ring and clamping washers, they need to be big enough to clamp the adaptor ring AND the stator plate
The YZ stator, you can see I filed the top slot wider to match the mounting screws in the TM case and the bottom one I cut out completely
