Honda BF20 BF2A Outboard Motors Manual, Page 42Get this manual
BFSO-BFSA bINSPECTION
CYLINDER ID
STANDARD 46.0 rnm (1.811 in) SERVICE LIMIT 46.050 mm (1.813 in)
If the service limit is exceeded, rebore the cylinder and install an oversize piston and piston rings
PISTON SKIRT OD
STANDARD 45.995 mm (1.8108 in) SERVICE LIMIT 45.920 mm (1.808 in)
PISTON-TO-CYLINDE CLEARANCE
STANDARD SERVICE LIMIT
0- 0.03 mm (0-0.0012 in)
0.13 rnm (0.0051 in)