Piston, Connecting Rod, and Bearings Cleaning and Inspection

Tools Required
• SA91101NE Feeler Gage Set
• SA9178NE-A Dial Bore Gage

1. Clean the piston:

Important

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

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




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




2. Inspect the piston diameter and oil clearance:
1. Using a micrometer, measure the piston diameter at a right angle to the piston pin hole center line, 5 mm (0.2 in) from the bottom of the piston.
Specification

Standard Piston Diameter Size Standard: 81.966-81.984 mm (3.227-3.2277 in)





2. Measure the cylinder bore diameter using a SA9178NE-A or equivalent, at 2 axis, transverse and longitudinal, 63.5 mm (2.5 in) from the top of the block. Average the 2 measurements together for determining the correct cylinder bore size and piston fit. Subtract the piston diameter, measured at 5 mm (0.2 in) from the bottom of the piston, measurement from the cylinder bore diameter measurement.
Specifications
Cylinder No. 1, 2, and 3
• Standard: 0.006-0.044 mm (0.0002-0.0017 in)
• Service Limit: 0.07 mm (0.0028 in) max.
Specifications
Cylinder 4
• Standard: 0.016-0.054 mm (0.0006-0.0021 in)
• Service Limit: 0.07 mm (0.0028 in) max.
3. If the clearance is greater than the maximum, replace the piston. If necessary, hone or bore each cylinder required and replace the piston. If necessary, replace the cylinder block.




3. Inspect the clearance between the flank of the piston ring groove and the new piston ring.
Using a SA91101NE or equivalent, measure the side clearance between the new piston ring and the flank of the piston ring groove. Specifications
Ring Groove Clearance
• No. 1 Ring Standard: 0.04-0.08 mm (0.0016-0.0032 in)
• No. 1 Ring Service Limit: 0.09 mm (0.0035 in) max.
• No. 2 Ring Standard: 0.03-0.08 mm (0.0012-0.0031 in)
• No. 2 Ring Service Limit: 0.08 mm (0.0031 in) max.
4. If the clearance is not within specifications, replace the piston and rings.




5. Inspect the piston ring end gap:
1. Insert the piston ring into the cylinder bore.
2. 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.
3. Using a SA91101NE or equivalent, measure the end gap.
Specifications
Standard End Gap
• No. 1 Ring Standard: 0.25-0.4 mm (0.0098-0.0157 in)
• No. 1 Ring Service Limit: 0.5 mm (0.0197 in) max.
• No. 2 Ring Standard: 0.25-0.5 mm (0.0098-0.0197 in)
• No. 2 Ring Service Limit: 0.6 mm (0.0236 in) max.
Specifications
Oil Ring (Side Rail)
• Standard: 0.25-1.25 mm (0.0098-0.0492 in)
• Service Limit: 1.4 mm (0.0551 in) max.
4. If the gap is greater than the maximum, replace the piston ring.




6. Check the piston bore diameter and pin diameter.
Specifications
Pin Diameter
• Standard: 19.496-19.5 mm (0.7676-0.7677 in)
• Service Limit: 19.496 mm (0.7676 in) min.
Specifications
Piston Pin Bore Diameter
• Standard: 19.502-19.507 mm (0.7678-0.768 in)
• Service Limit: 19.507 mm (0.768 in) max.
Specifications
Oil Clearance
• Standard: 0.002-0.011 mm (0.0001-0.0004 in)
• Service Limit: 0.011 mm (0.0004 in) max.
7. Oil the pin and push it into the piston with your thumb. The pin must rotate freely when centered in the piston pin bore.




8. Check the connecting rod bushing and large end diameters.
Specifications
Rod Bushing Diameter
• Standard: 19.42-19.506 mm (0.767-0.7685 in)
• Service Limit: 19.526 mm (0.769 in) max.
Specifications
Large End Bore Diameter
• Standard: 50.193-50.207 mm (1.9761-1.9767 in)
• Service Limit: 50.207 mm (19.767 in) max.





Important

When replacing the connecting rod, always replace the bearings.

9. Inspect the connecting rods:
1. Using a rod aligner, check the connecting rod alignment. Check for bend.
The maximum bend per 100 mm (3.94 in) is 0.28 mm (0.011 in) max. If bend is greater than the maximum, replace the connecting rod assembly.
2. Check for twist.
The maximum twist per 100 mm (3.94 in) is 0.32 mm (0.0126 in) max. If twist is greater than the maximum, replace the connecting rod assembly.