2001 Edition Yamaha F225A and LF225A Outboards Service Manual, Page 133Get this manual
Cylinder head NOTE: Turn the valve guide reamer clockwise to ream the valve guide Do not turn the reamer counterclockwise when removing the reamer
Valve guide reamer: YB-06804 4Measure the valve guide inside diameterReplace the valve guide if out of specificationValve guide inside diameter: 5.5045.522 mm (0.21670.2174 in)
Checking the valve seat
1Eliminate carbon deposits from the valve with scraper2Apply thin, even layer of Mechanic's blueing dye (Dykem) onto the valve seat3Lap the valve slowly on the valve seat with valve lapper (commercially obtainable) as shownValve seat contact width a: Intake: 1.11.4 mm (0.0430.055 in) Exhaust: 1.41.7 mm (0.0550.067 in)