Overhaul

CYLINDER AND PISTON





1. 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 (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: 99.505 - 99.515 mm (3.9175 - 3.9179 in)
B: 99.495 - 99.505 mm (3.9171 - 3.9175 in)





2. Measure 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 (68 degrees F).
Taper:
Standard 0.015 mm (0.0006 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, select a suitable sized piston by measuring the piston clearance.
4. Measure outer diameter of each cylinder.
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 (68 degrees F).

Piston grade point H. 38.2 mm (1.50 in)
Piston outer diameter.
Standard
A: 99.505 - 99.515 mm (3.9175 - 3.9179 in)
B: 99.495 - 99.505 mm (3.9171 - 3.9175 in)
0.25 mm (0.0098 in) oversize 99.745 - 99.765 mm (3.9270 - 3.9278 in)
0. 50 mm (0.0197 in) oversize 99.995 - 100.015 mm (3.9368 - 3.9376 in)





5. Calculate the clearance between cylinder and piston.

NOTE: Measurement should be performed at a temperature of 20 degrees (68 degrees F).

Cylinder to piston clearance at 20 degrees (68 degrees F).
Standard -0.010 - 0.010 mm (-0.00039 - 0.00039 in)

6. Boring and honing
1. If any of the measured value of taper, out-of-roundness or cylinder-to-piston clearance is out of standard or if there is any damage on the cylinder wall, rebore it to replace with an oversize piston.

CAUTION: When any of the cylinders needs reboring, all other cylinders must be bored at the same time, and replaced with oversize pistons.

2. If the cylinder inner diameter exceeds the limit 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, when measuring the cylinder diameter, wait until it has cooled to room temperature.

Cylinder inner diameter boring limit (diameter): 100.005 mm (3.9372 in)

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 and 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 (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.