6. Inspection of Piston and Connecting Rod Assemblies

1. Clean piston:

NOTICE: 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:
a. Using a micrometer, measure the piston diameter at a right angle to the piston pin hole center line, 5 mm (0.20 in.) from the bottom of the piston.





Standard Piston Diameter:
Size:
Standard: 81.966-81.984 mm (3.2270-3.2277 in.)

b. Measure the cylinder bore diameter using a dial bore gauge, Service Tool SA9178NE (or equivalent) at two axis (transverse and longitudinal) 63.5 mm (2 1/2 in.) 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 in.) 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 in.)
Service Limit: 0.070 mm (0.0028 in.) max.

Cylinder No. 4:
Standard: 0.016-0.054 mm (0.0006-0.0021 in.)
Service Limit: 0.070 mm (0.0028 in.) 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 Service Tool SA91101NE (or equivalent), measure side clearance between new piston ring and the flank of the piston ring groove.

Ring Groove Clearance:
Standard: No. 1 Ring: 0.030-0.080 mm (0.0012-0.0031 in.)
Standard: No. 2 Ring: 0.040-0.080 mm (0.0016-0.0032 in.)
Service Limit: No. 1 Ring: 0.090 mm (0.0035 in.) max.
Service Limit: No. 2 Ring: 0.080 mm (0.0031 in.) 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 in.]) from the top surface of the cylinder sleeve or block.
c. Using a feeler gauge SA91101NE (or equivalent), measure the end gap.

Standard End Gap:
Standard: No. 1 Ring 0.250-0.400 mm (0.0098-0.0157 in.)
Service Limit: No. 1 Ring: 0.500 mm (0.0197 in.) max.
Standard Ring 2: No. 0.250-0.400 mm (0.0098-0.0157 in.)
Service Limit: No. 2 Ring:0.600 mm (0.0236 in.) max.

Oil Ring (Side Rail):
Standard: 0.250-1.25 mm (0.0098-0.0492 in.)
Service Limit: 1.400 mm (0.0551 in.) 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 in.)
Service Limit: 19.496 mm (0.7676 in.) min.

Piston Pin Bore Diameter:
Standard: 19.502-19.507 mm (0.7678-0.7680 in.)
Service Limit: 19.507 mm (0.7680 in.) max.

Oil Clearance:
Standard: 0.002-0.011 mm (0.0001-0.0004 in.)
Service Limit: 0.011 mm (0.0004 in.) 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.





6. Check connecting rod bushing and large end diameters:

Rod Bushing Diameter:
Standard: 19.420-19.506 mm (0.7670-0.7685 in.)
Service Limit: 19.526 mm (0.769 in.) max.

Large End Bore Diameter:
Standard: 50.193-50.207 mm (1.9761-1.9767 in.)
Service Limit: 50.207 mm (1.9767 in.) max.





7. Inspect connecting rods:
a. Using a rod aligner, check the connecting rod alignment. Check for bend.

Maximum bend per 100 mm (3.94 in.): 0.28 mm (0.011 in.) max.
If bend is greater than maximum, replace the connecting rod assembly.

b. Check for twist.

Maximum twist per 100 mm (3.94 in.): 0.320 mm (0.0126 in.) max.
If twist is greater than maximum, replace the connecting rod assembly.

IMPORTANT: When replacing the connecting rod, always replace the bearings.