Overhaul
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.
Standard diameter.
A: 89.205 - 89.215 mm (3.5120 - 3.5124 in)
B: 89.195 - 89.205 mm (3.5116 - 3.5120 in)
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 degrees C (68 degrees F).
Cylindricality.
Standard 0.030 mm (0.0012 in)
Out-of-roundness:
Standard 0.010 mm (0.0004 in)
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:
NOTE: 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).
Piston grade point H. 37.3 mm (1) 4685 in)
Piston outer diameter.
Standard
A: 89.205 - 89.215 mm (3.5120 - 3.5124 in)
B: 89.195 - 89.205 mm (3.5116 - 3.5120 in)
0.25 mm (0.0098 in) oversize
89.445 - 89.465 mm (3.5215 - 3.5222 in)
0.50 mm (0.0197 in) oversize
89.695 - 89.715 mm (3.5313 - 3.5321 in)
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 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.
PISTON AND PISTON PIN
1. Check the piston and piston pin for breaks, cracks or wear. Replace if faulty.
2. Check the piston ring groove for wear or damage. Replace if faulty.
3. Make sure that the piston pin can be inserted into the piston pin hole with a thumb at 20 degrees C (68 degrees F). Replace if faulty.
Standard clearance between piston pin and hole in piston:
Standard 0.004 - 0.008 mm (0.0002 - 0.0003 in)
4. Check the snap ring installation groove (A) on the piston for burr. If necessary, remove burr from the groove so that the piston pin can lightly move.
5. Check the piston pin snap ring for distortion, cracks and wear.