Honda BF50 (5HP), BF5A Outboard Motors Shop Manual 2014, Page 44Get this manual
BF50BF5A bINSPECTION VALVE SPRING FREE LENGTH
Measure the free length of the valve springsSTANDARD 29.0 mm (1.142 in) SERVICE LIMIT 28.1 mm (1.106 in)
Replace the springs if they are shorter than the service limit
VALVE SEAT WIDTH
Measure the valve seat width STANDARD 0.8 mm (0.031 in) SERVICE LIMIT 1.8 mm (0.07 in)
If the valve seat width is under the standard, or over the service limit, recondition the valve seat(P.44-46)
CYLINDER HEAD
Remove carbon deposits from the combustion chamberClean off any gasket material from the cylinder head surfaceCheck the spark plug hole and valve areas for cracksCheck the cylinder head for warpage with straight edge and feeler gaugeSERVICE LIMIT 0.10 mm (0.004 in)