Honda BF8, BF9.9 and BF10 Outboard Motors Shop Manual., Page 167Get this manual
4) Remove and inspect the valve seat faceThe valve seat contact should be within the specified width and even all around the circumferenceStandard 0.91.1 rnm (0.0350.043 in) Service limit 2.0 mm (0.08 in)
Inspect the valve seat face for: Uneven seat width: replace the valve and reface the valve seatDamaged face: replace the valve and reface the valve seatContact area too high or too low: reface the valve seatThe valve cannot be groundIf the valve face is burned or badly worn or if it contacts the seat unevenly, replace the valve[I] UNEVEN SEAT WIDTH
1 TOO HIGH 2