Talk really nicely to Lozza
If you run a CR125 piston, check your compression pressure as they have a higher and "fuller" dome than stock. Be especially carefull if you trim the underside of the cylinder to correct the piston to deck height.
YZ80 ignition works very well and allows the motor to make more power at higher revs.
I had a few problems with mine at the Nationals but I think I have them sorted now, I just need time to get it out to ride it again.
Then I need to make a new pipe
I'm still running a standard carb too (26mm)
Suspension! a good set of rear shocks and PD valves or Emulators for the forks and heavier springs. You'll need to make adaptors or new tops for the damper rods to fit damping vlaves but they are very well worth it.
Maybe not a CR beater but a lot faster than stock