1983-1985 Original Honda ATC 200X Shop Manual, Page 64Get this manual
CYLINDER HEADVALVES
Use 60 degree cutter to remove the bottom 14 of the old seatRemove the cutter and inspect the area you have just removed
Install 45 degree finish cutter and cut the seat to the proper width
Make sure that all pitting and irregularities are removedRefinish if necessary
1.1-1.3mm (0.044-0.052 in)
Apply thin coating of Prussian Blue to the valve seatPress the valve through the valve guide and onto the seat to make clear pattern