Thanks so much!This service manual should answer all your questions. https://mymowerparts.com/pdf/Tecums...-OVRM120-OVXLC120-OVXL120-OVXL125-695244A.pdf
Thank YouSet each valve to .004 inch where feeler gauge just fits with a slight drag between the rocker tip and valve stem. Do this with engine cold and plug removed.
Page 84 has the specs page. The procedure is explained just prior.