Ok Pete , this is what I have found, on my 2000 kdx 220,
Clearance minium .8 to 1mm. I cann't remember the squish angle , but 35 deg rings a bell. But just clean it up on the factory angle. I have and RB head and it is cleaned up on the factory angle , with a squish band 9mm wide, the head recess is .7mm, which gave me a 1.1mm clearance. I also have my own head that I have machined.This head was butched by someone who was supost to know what he was doing, I thought it would be easier and quicker to pay someone to do it right, only to pay out money and then have to do the job my self ot fix it , even after giving detailed instructions , This is what I ended Up with after a few experiments, and I how run all the time, heaps more bottom end, but you do have to machine a lot out. Squish is recessed .5 mm , squish band width is increased to 10mm and then the bowl area edges are squared up to 75 deg. If you need cc's I will have to pull it off to measure. hope this helps, good luck