Piston: Testing and Inspection

1. Clean piston:

CAUTION: Do not damage the piston's aluminum surfaces during cleaning.

a. Using a gasket scraper, remove the carbon from the piston top.
b. Using a soft brush and solvent, thoroughly clean the piston.





c. Using a groove cleaning tool or broken ring, clean the ring grooves.





2. Inspect piston diameter and oil clearance using a micrometer, measure the piston diameter at a right angle to the piston pin hole center line, 5 mm (0.20 inch) from the bottom of the piston.
a. Standard piston diameter size is 81.966-81.984 mm (3.2270-3.2277 inch).





b. Measure the cylinder bore diameter using a dial bore gauge, Service Tool at two axis (transverse and longitudinal) 63.5 mm (2 1/2 inch) from top of block. Average the two measurements together for determining correct cylinder bore size and piston fit. Subtract the piston diameter (measured at 5 mm [0.200 inch] from the bottom of the piston) measurement from the cylinder bore diameter measurement.
Cylinder No. 1, 2, and 3:
^ Standard: 0.006-0.044 mm (0.0002-0.0017 inch).
^ Service Limit: 0.070 mm (0.0028 inch) max.
Cylinder No. 4:
^ Standard: 0.016-0.054 mm (0.0006-0.0021 inch).
^ Service Limit: 0.070 mm (0.0028 inch) max.
If the clearance is greater than maximum, replace the piston. If necessary, hone or bore each cylinder required and replace the piston. If necessary, replace the cylinder block.
3. Inspect clearance between flank of piston ring groove and new piston ring.





a. Using a feeler gauge measure side clearance between new piston ring and the flank of the piston ring groove.
Ring Groove Clearance:
^ Standard: No. 1 Ring: 0.040-0.080 mm (0.0016-0.0032 inch).
^ Service Limit: No. 1 Ring: 0.090 mm (0.0035 inch) max. 0.030-0.080 mm (0.0012-0.0031 inch).
^ Service Limit: No. 2 Ring: 0.080 mm (0.0031 inch) max.
If the clearance is not within specification, replace the piston and rings.





4. 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 (100 mm [3.94 inch]) from the top surface of the cylinder sleeve or block.
c. Using a feeler gauge measure the end gap.
Standard End Gap:
^ Standard: No. 1 Ring: 0.250-0.400 mm (0.0098-0.0157 inch).
^ Service Limit: No. 1 Ring: 0.500 mm (0.0197 inch) max.
^ Standard: No. 2 Ring: 0.250-0.500 mm (0.0098-0.0197 inch).
^ Service Limit: No. 2 Ring: 0.600 mm (0.0236 inch) max.
Oil Ring (Side Rail):
^ Standard: 0.250-1.25 mm (0.0098-0.0492 inch).
^ Service Limit: 1.400 mm (0.0551 inch) max.
If the gap is greater than maximum, replace the piston ring.





5. Check piston pin bore diameter and pin diameter.
Pin Diameter:
^ Standard: 19.496-19.500 mm (0.7676-0.7677 inch).
^ Service Limit: 19.496 mm (0.7676 inch) min.
Piston Pin Bore Diameter:
^ Standard: 19.502-19.507 mm (0.7678-0.7680 inch).
^ Service Limit: 19.507 mm (0.7680 inch) max.
Oil Clearance:
^ Standard: 0.002-0.011 mm (0.0001-0.0004 inch).
^ Service Limit: 0.011 mm (0.0004 inch) max.
Oil the pin and push it into the piston with your thumb. The pin must rotate freely when centered in the piston pin bore.