Cylinder and Piston
CYLINDER AND PISTON1) The cylinder bore size is stamped on the front upper face of the cylinder block.
NOTE:
^ Measurement should be performed at a temperature of 20°C (68°F).
^ Standard sized pistons are classified into two grades, "A" and "B". These grades should be used as guide lines in selecting a standard piston.
2) How to measure the inner diameter of each cylinder: Measure the inner diameter of each cylinder in both the thrust and piston pin directions at the heights as shown in the figure, using a cylinder bore gauge.
NOTE: Measurement should be performed at a temperature of 20°C (68°F).
3) When the piston is to be replaced due to general or cylinder wear, determine a suitable sized piston by measuring the piston clearance.
4) How to measure the outer diameter of each piston: Measure the outer diameter of each piston at the height as shown in the figure. (Thrust direction)
NOTE: Measurement should be performed at a temperature of 20°C (68°F).
5) Calculate the clearance between cylinder and piston.
NOTE: Measurement should be performed at a temperature of 20°C (68°F).
Cylinder to piston clearance at 20°C (68°F):
Standard: -0.010 - 0.010 mm (-0.0004 - 0.0004 in)
6) Boring and honing:
1) If the value of cylindrically, out-of-roundness, or cylinder-to-piston clearance measured is out of standard or if there is any damage on the cylinder wall, rebore it to use an oversize piston.
CAUTION:
^ When any of the cylinders needs reboring, other cylinders must be bored at the same time, and replaced with oversize pistons.
^ Do not perform boring on one cylinder only.
^ Do not replace only a single cylinder for an oversize piston.
2) If the cylinder inner diameter exceeds the limit after boring and honing, replace the cylinder block.
Cylinder inner diameter boring limit (diameter): To 89.715 mm (3.5321 in)
NOTE: Immediately after reboring, the cylinder diameter may differ from its real diameter due to temperature rise. Thus, pay attention to this when measuring the cylinder diameter.