2009 Yamaha F40 Outboard Service Manual, Page 218Get this manual
Camshaft and valve
Replacing the valve guide
After replacing valve guide, check the valve seat contact area1Remove the valve guide from the combustion chamber side using the special service tool b
Turn the valve guide reamer clockwise to ream the valve guide Do not turn the reamer counterclockwise when removing it Make sure to clean the valve guide after reaming it4Measure the valve guide inside diameterValve guide inside diameter: 5.5005.512 mm (0.21650.2170 in)
Checking the valve seat
1Eliminate any carbon deposits from the valves