Honda BF50 (5HP), BF5A Outboard Motors Shop Manual 2014, Page 56Get this manual
BF5CBF5A PISTON RING SIDE CLEARANCE
STANDARD TOPSECOND OIL 0.Q15-0.045 mm (0.0006-0.0018 in) SERVICE LIMIT 0.10 mm (0.004 in)
PISTON RING END GAP
STANDARD TOPSECOND OIL 0.15-0.35 mm (0.006-0.014 in) SERVICE LIMIT 0.50 mm (0.020 in) PISTON RING
Before measuring the end gapuse the piston top to position the ring so it will not be cocked in the cylinder bore