Yamaha Outboard F15A F9.9C, FT9.9D F15 Service Manual, Page 238Get this manual
CAMSHAFT AND VALVES
Valve seat refacing
After refacing the valve seat or replacing the valve and valve guide, lap the valve seat and valve face
8 To prevent chatter marks, turn the valve seat cutter clockwise with an even, downward pressure (4kg)8 Rotate the cylinder head to maintain an even