Piston: Testing and Inspection

CHECK FIT BETWEEN PISTON AND PISTON PIN
1. Try to move the piston back and forth on the piston pin.
2. If any movement is felt, replace the piston and pin as a set.





CLEAN PISTON
1. Using a gasket scraper or other suitable tool, remove the carbon from the piston top.





2. Using a suitable groove cleaning tool or broken ring, clean the piston ring grooves.
3. Using suitable solvent and a brush, thoroughly clean the piston.

NOTE: Do not use a wire brush.

INSPECT PISTON
1. Inspect piston oil clearance as follows:





- Using a micrometer, measure the piston diameter at right angles to the piston pin center line, 34.000 mm (1.3400 inch) from the piston head.
Piston diameter: 85.935-85.945 mm (3.3833-3.3837 inch).
- Measure the cylinder bore diameter in the thrust directions. (See Cylinder Block Assembly Testing and Inspection)
- Subtract the piston diameter measurement from the cylinder bore diameter measurement.
Standard oil clearance: 0.055-0.078 mm (0.0022-0.0031 inch).
Maximum oil clearance: 0.100 mm (0.0039 inch).
- If the oil clearance is greater than maximum, replace all the 6 pistons.
- If necessary, replace the cylinder block.
2. Inspect piston ring groove clearance as follows:





- Using a feeler gauge, measure the clearance between new piston ring and the wall of the piston ring groove.
Ring groove clearance:
No. 1: 0.011-0.070 mm (0.0004-0.0028 inch).
No. 2: 0.030-0.070 mm (0.0012-0.0028 inch).
- If the clearance is not as specified, replace the piston.





3. Inspect piston pin fit as follows:
- At 80° C (176° F), you should be able to push the piston pin into the piston pin hole with your thumb.