ES002 MSS ENGINE

May I please know the diameter of Iron MSS inlet and exhaust valves. 
My head(s) were so worn when I started I never did use a standard size valve.
It is time for a rebuild and time to bush the seats back to original, if only I knew what original was? - Bob Gussman 24/11/2004

Having purchased a copy of the original factory drawings from Owen Dea'th, the answer is 1.687 inches or 1-11/16 - Bob Gussman 27/12/2004