29. Piston, Connecting Rod, and Bearing Clean and Inspect

Piston, Connecting Rod, and Bearings Cleaning and Inspection





Important: Use compressed air to dry the connecting rod. DO NOT use shop towel or rag to clean the rod cap and the rod mating surfaces.

1. Use cleaning solvent to clean the connecting rod.
2. Use cleaning solvent to clean the pistons if reusing the piston. DO NOT wire brush the piston skirt or the ring groove area.
3. Use cleaning solvent to clean the piston pins if reusing the piston pins. New pistons contain new piston pins.
4. Use a groove cleaner or broken ring to clean the piston ring groove.





5. Inspect the connecting rod for the following conditions:
^ Inspect for twists. Replace if damage is evident.
^ Inspect for nicks. Replace if damage is evident.
^ Inspect for cracks. Replace if damage is evident.





6. Inspect the pistons for the following conditions:
^ Inspect for cracked skirts.
^ Inspect for cracked piston pin bosses.
^ Inspect for cracked ring groove lands.
^ Inspect for nicks that may cause binding.
^ Inspect for burrs that may cause binding.
^ Inspect for warped ring groove lands.
^ Inspect for worn ring groove lands.
^ Inspect for eroded areas on top of the piston.
^ Inspect for worn piston pin bores.
^ Replace the piston if any of the above is evident.
7. Measure the piston ring groove clearance.
8. Replace the piston if the ring groove clearance is not within the proper specification.
The 1st and 2nd compression ring groove clearance specification is 0.02 - 0.04 mm (0.0008 - 0.0015 inch).
9. Replace the piston if the ring groove clearance is not within the proper specification.
The oil control ring groove clearance specification is 0.01 - 0.02 mm (0.0004 - 0.0012 inch).





10. Use a micrometer and an inside micrometer to measure the piston pin bore-to-piston pin clearance. The maximum clearance is 0.003 - 0.008 mm (0.0001 - 0.0003 inch).
11. Replace the piston and replace the pin if the pin bore-to-piston pin clearance is beyond the proper specification.





12. Measure the piston ring end gap clearance in the bore. Perform only after the cylinder has been honed.
13. Replace the piston rings if the end gap clearance is not within the proper specification.
The 1st and 2nd compression ring gap specification is 0.30 - 0.50 mm (0.0118 - 0.0196 inch).
14. Replace the piston rings if the end gap clearance is not within the proper specification.
The oil control ring end gap specification is 0.40 - 1.40 mm (0.0157 - 0.0551 inch).