Honda Outboards BF40A/BF50A Service Manual, Page 115Get this manual
HONDABF35A45A VALVE SEAT WIDTH
STANDARD SERVICE LIMIT
1.25-1.55 mm
{0.049-0.061 in}
2.0 mm (0.08 in)
5) Make light pass with 45 cutter to remove any possible burrs at the edges of the seat 6} After resurfacing the seats, inspect for even valve seating
0.95-1.25 mm (0.037-0.049 in)
Apply Prussian Blue compound or erasable felt-tipped marker ink to 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 transfered marking compoundshould have good contact all the way around7} Lap the valves into their seats, using hand valve lappar