Piston and Connecting Rod Clean and Inspect

NOTE: Do not use a wire brush in order to clean any part of the piston.

1. Clean the connecting rod in cleaning solvent.
2. Dry the connecting rod with compressed air.
3. Clean the varnish from the piston skirts and the pins with the cleaning solvent.
4. Clean the piston ring grooves with a groove cleaner.
5. Clean the piston oil ring holes and the slots.
6. Inspect the connecting rod for twisting, nicks, and crack. Replace any damaged connecting rods.
7. Inspect the pistons for the following conditions:
- Cracked ring lands, skirts, or pin bosses
- Nicks or the spurs in the grooves that may cause binding
- Warped or worn ring lands
- Scuffed or damaged skirts
- Eroded areas at the top of the piston
- Worn piston bores and piston pins
8. Replace pistons that are damaged or show signs of excessive wear.
9. Measure the pin bore-to-piston clearance.
a. The piston pin bores and the piston pins must be free of varnish or scuffing when being measured.
b. Use a micrometer in order to measure the piston pin. Use an inside micrometer in order to measure the piston pin bore.
c. Replace the piston and piston pin if the clearance is in excess of 0.025 mm (0.0010 inch).
d. Match piston and piston pin. Do not service separately.
10. Measure the piston compression ring end gap.

NOTE: Fit each compression ring to the cylinder in which it will be used.

a. Place the compression ring into the cylinder bore.
b. Push the compression ring into the cylinder bore to approximately 6.5 mm (0.25 inch) above the ring travel.

NOTE: The ring must be square to the cylinder wall.

c. Use a feeler gage in order to measure the end gap.
- Piston Compression Ring Gap:
Production
Top: 0.30-0.58 mm (0.012-0.022 inch)
2nd: 0.51-0.71 mm (0.020-0.028 inch)
Service
Top: 0.30-0.85 mm (0.012-0.025 inch)
2nd: 0.46-0.90 mm (0.016-0.035 inch)
- Piston Oil Ring Gap:
Production: 0.25-0.76 mm (0.010-0.030 inch)
Service: 0.25-0.785 mm (0.010-0.030 inch)

d .Select another size ring set if the end gap exceeds specifications.





11. Measure the piston ring side clearance.
- Piston Compression Ring Groove Clearance:
Production
Top: 0.030-0.070 mm (0.0012-0.0027 inch)
2nd: 0.040-0.080 mm (0.0015-0.003 inch)
Service Limit
Top: 0.030-0.090 mm (0.0012-0.0035 inch)
2nd: 0.040-0.0100 mm (0.018-0.026 inch)
- Piston Oil Ring Groove Clearance
Production: 0.051-0.17 mm (0.002-0.006 inch)
Service: 0.051-0.22 mm (0.002-0.009 inch)

a. Roll the piston ring entirely around its ring groove on the piston.
b. Dress the groove with a fine cut file if the ring groove causes binding.
c. Replace the piston ring if a distorted piston ring causes binding.
d. Use a feeler gage in order to measure the side clearance of the piston ring and groove.
e. Try another piston ring if the side clearance is too small.