Pulled the head & cylinder for the first time since I bought the quad.
I am going to do all machining myself.
I inspected the cylinder for taper,roundness, & size. To my surprise it is bored .100 over.Bore probes at 68.532mm (2.6981"). (Taper and roundness were both under .001" (Honda spec). I am going to run a wiesco brush hone in it, clean and fine sand any port burs. I will go with the lighter cast pro x piston and change it every 30 hours of riding. I plan on drilling 2 small diamiter holes on center of the front of the piston right behind the exaust bridge for more oil lubrication (if they aren't already there)
I'm hoping the piston diamiter will allow for a .0025" clearance to the cylinder. My 85ATC manual says .006" piston to cylinder clearance is the service limit. I will see when the piston arives. If its pushing .004" i think I will order the 69mm piston and machine the O.D. (outside diamiter) down to obtain a .0025 clearance to my bore size.
I'm sticking with the stock head. I'm going to machine the squish area widening that to match bore. While holding the same angle that is on the stock atc250r head. I don't know this angle yet but I think it's around 10° but I will check this with my lathe compond.