2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 108Get this manual
Cylinder block
Checking the piston ring side clearance
1Measure the piston ring side clearanceReplace the piston and piston rings as set if out of specification
S63P5730
Piston ring end gap d: Top ring: 0.150.30 mm (0.00590.0118 in) Second ring: 0.700.90 mm (0.02760.0354 in) Oil ring: 0.200.70 mm (0.00790.0276 in) Measuring point e: 20 mm (0.8 in)
Piston ring side clearance: Top ring a: 0.040.08 mm (0.00160.0031 in) Second ring b: 0.030.07 mm (0.00120.0028 in) Oil ring c: 0.030.15 mm (0.00120.0059 in)