Yamaha F100B F100C Outboards Factory Service Manual, Page 120Get this manual
Power unit
Checking the valve guides
NOTE: Use the valve guide clearance calculation method or the valve runout measurement method to check the valve guides Before checking the valve guide make sure that the valve stem diameter is within specification1Measure the valve guide inside diameter a
Valve margin thickness a: Intake: 0.81.2 mm (0.0310.047 in) Exhaust: 1.01.4 mm (0.0390.055 in) 3Measure the valve stem diameter bReplace if out of specification
Valve stem diameter b: Intake: 5.975.99 mm (0.23500.2358 in) Exhaust: 5.965.97 mm (0.23470.2350 in) 4Measure the valve stem runoutReplace if out of specification