A while back I had a request to post this if I found it, can't remember who was looking for the spec, but I ran across it today. This is from the 84 TRX200 on page 6-7 which is effectively the same engine as the ATC200ES. The gap spec should be very similar for all of the similar engines, and likely not a bad number to base for other models as well.

0.4-0.65mm (0.015-0.025in)



Hopefully someone finds this useful. Also don't forget to check that the rotor moves freely and springs back well while you're in that area of the engine.