I'm rebuilding a CH20 64554 out of a Walker mower. I got it cheap because it needed a head gasket. I replaced the head gaskets, and that helped, but it was still burning too much oil. I tore it apart again to replace the rings. While I have it apart the second time I am trying to be more diligent about replacing worn items. The valve stems appeared to me to be out of spec. The Kohler manual says the intake valve stem diameter should be no smaller than 6.982mm and the exhaust 6.97mm. Mine were 6.93mm (intake) and 6.94mm (exhaust). So I ordered new valves from Lil Red Barn ($80). I was surprised to discover the new valves were no better. The stem diameter on the new intake valves is 6.94mm and the exhaust 6.95mm. My guides appear to be in spec but if I put the new valves in the "Valve Stem-to-Valve Guide Running Clearance" is going to be out of spec. Should I return the new valves and just run the old ones? Or keep hunting for OEM valves? Or just run the new ones? I am doubting myself because I was watching a Youtube video on measuring valve stem diameter that recommended comparing the worn part of the stem (the part that wears against the guide) to the rest of the stem. On my old valves, even though they are out of spec, they appear to be out of spec for the entire stem. There isn't really a worn spot. Of course, the old valves may not be OEM either. Any advise appreciated. I might take the head, new valves, and old valves to a local machine shop and have them check it out. Maybe they can knurl & ream the head enough to get it within spec. Another option is to exchange these for the .25 over valves and have the guides reamed to fit.