Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 116Get this manual
VALVE SEAT WIDTH STANDARD 0.9-1.1 mrn
(0.035-0.043 in) SERVICE LIMIT
2.0 rnm (0.08 in)
0.9-1.1 mm (0.035- 0.043 in)
5) Make light pass with 45O cutter remove any possible burrs at the edges of the seat6) After resurfacing the seats, inspect for even valve seatingApply Prussian Blue compound or erasable, felt-tipped marker ink the valve facesInsert the valves, and then lift them and snap them closed against their seats several timesBe sure the valve does not rotate on the seatThe seating surface, as shown by the transferee! marking compound, should have good contact all the way around7) Lap the valves into their seats, using hand valve lapper and lapping compound (commercially available)CAUTION