The valves are adjusted by loosening a 10 mm jam nut and checking the clearance with a feeler gauge. A certain procedure must be followed. Just Google "denlors valve adjustment article" for detailed "how to" instructions for most 4cyl Honda engines.
There should be a placard under the hood listing the valve clearance.
12 and 16 valve engines
Intake and auxiliary valves
.007 to .009 in (.17 to .22mm)
Exhaust Valves (carbureted 12...