Piston: Testing and Inspection
PISTON INSPECTION1. Clean piston.
(a) Using a gasket scraper, remove the carbon from the piston top.
(b) Using a groove cleaning tool or broken ring, clean the ring grooves.
(c) Using a soft brush and solvent, thoroughly clean the piston.
CAUTION: Do not damage the piston.
2. Inspect piston.
A. Inspect piston oil clearance.
NOTE: There are 3 sizes of the standard piston diameter, marked "1", "2" and "3" accordingly. The mark is stamped on the piston top.
(a) Using a micrometer, measure the piston diameter at right angles to the piston pin center line, 26 mm (1.02 inch) from the piston head.
Piston diameter:
STD:
Mark "1": 85.870 - 85.880 mm (3.3807 - 3.3811 inch)
Mark "2": 85.880 - 85.890 mm (3.3811 - 3.3815 inch)
Mark "3": 85.890 - 85.900 mm (3.3815 - 3.3819 inch)
O/S 0.50: 86.370 - 86.400 mm (3.4004 - 3.4016 inch)
(b) Measure the cylinder bore diameter in the thrust directions. Testing and Inspection
(c) Subtract the piston diameter measurement from the cylinder bore diameter measurement.
Standard oil clearance: 0.12 - 0.14 mm (0.0047 - 0.0055 inch)
Maximum oil clearance: 0.16 mm (0.0063 inch)
If the oil clearance is greater than maximum, replace all 4 pistons and rebore all the 4 cylinders. If necessary, replace the cylinder block.
NOTE: (Use new cylinder block): Use a piston with the same number mark as the cylinder bore diameter marked on the cylinder block.
B. Inspect piston ring groove clearance.
Using a feeler gauge, measure the clearance between new piston ring and the wall of the ring groove.
Ring groove clearance: 0.030 - 0.070 mm (0.0012 - 0.0028 inch)
If the oil clearance is greater than maximum, replace the piston.
C. Inspect piston ring end gap.
(a) Insert the piston ring into the cylinder bore.
(b) Using a piston, push the piston ring a little beyond the bottom of the ring travel, 110 mm (4.33 inch) from the top of the cylinder block.
(c) Using a feeler gauge, measure the end gap.
Standard end gap:
No. 1: 0.270 - 0.500 mm (0.0106 - 0.0197 inch)
No. 2: 0.270 - 0.510 mm (0.0106 - 0.0201 inch)
Oil (Side rail): 0.200 - 0.550 mm (0.0079 - 0.0217 inch)
Maximum end gap:
No. 1: 1.10 mm (0.0433 inch)
No. 2: 1.11 mm (0.0437 inch)
Oil (Side rail): 1.15 mm (0.0453 inch)
If the end gap is greater than maximum, replace the piston ring. If the end gap is greater than maximum, even with a new piston ring, rebore all the 4 cylinders or replace the cylinder block.
D. Inspect piston pin fit.
At 60° C (140° F), you should be able to push the piston pin into the piston pin hole with your thumb.