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 degrees C (68 degrees 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) Measurement method for cylinder inner diameters:
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 degrees C (68 degrees F).
3) When the piston is to be replaced due to general or cylinder wear, select 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 degrees C (68 degrees F).
5) Calculate the clearance between cylinder and piston.
NOTE:
Measurement should be performed at a temperature of 20 degrees C (68 degrees F).
Cylinder to piston clearance at 20 degrees C (68 degrees F).
Standard
-0.010 - 0.010 mm (-0.0004 - 0.0004 in)
6) Boring and honing:
1) If the value of cylindricality, 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, all other cylinders must be bored at the same time, and use oversize pistons.
^ Do not perform boring on one cylinder only. Nor use an oversize piston for one cylinder only.
2) If the cylinder inner diameter exceeds 92.515 mm (3.6317 in) after boring and honing, replace the cylinder block.
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.