2004 SR Johnson 2-stroke 40, 50HP Service Manual, Page 193Get this manual
POWERHEAD INSPECTION Cylinder head warpage must not exceed 0.003 in (0.08 mm) per inch of measurementReplace head if warpage exceeds this dimensionMeasure each cylinder in at least two areasEach area should be measured twiceThe difference between the two measurements in each area is the cylinder out-of-round dimension The cylinder must not be out-of-round by more than 0.003 in(0.08 mm)The dimensional difference between the two areas is cylinder taper The cylinder taper must not exceed 0.002 in(0.05 mm)
Crankshaft
Measure the diameter of each crankpin and main bearing journalThe lower main bearing journal would only be measured if the bearing was removed for another reason1Measurement areas
The difference between your measurements and standard bore is cylinder oversizeFor dimensions, refer to TECHNICAL DATA on p26 The cylinder must not be oversize by more than 0.003 in(0.08 mm)
Cylinder Bore
Use Cylinder Bore Gauge, PIN 771310, to inspect each cylinder bore for an out-of-round, oversize, or tapered conditionBe sure the gauge is perfectly square in the bore when measuring