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

Caution: Bodily injury may occur if the carburetor cleaning fluid is exposed to the skin or if the fumes are inhaled.





1. Clean the sludge and carbon from the following components:
^ The piston
^ The piston pin
^ The connecting rod

Notice: Do not cut the ring groove with a file or a rough edged tool. Good performance and durability depends on the straightness and smoothness of the ring groove.

2. Clean the piston ring grooves of all carbon.

Important: Do not scrape the piston skirt. Do not mark or score the sides of the ring groove.

3. Soak the piston pin in carburetor cleaning solution to remove varnish.





4. Use the following procedure to inspect the connecting rod for bending or twisting.
4.1. Install the connecting rod cap and bolts. Tighten to specifications.
4.2. Place the connecting rod assembly on a checking fixture and check for bending or twisting.
4.3. Replace the connecting rod if bent more than 0.127 mm (0.010 inch).
4.4. Check new connecting rods before use.





5. Inspect the outside of the connecting rod bearing and the inside diameter of the connecting rod bearing journal for wear indicating high spots.





6. Check the connecting rod cap bolts for stretch (compare to known good bolt). (1) is a stretched bolt, (2) is a new or good bolt.





7. Inspect the piston for the following conditions:
^ Scoring of the skirt (2)
^ Cracks
^ Broken ring groove lands
^ Wear (1)

8. Inspect the upper end of the connecting rod for scoring.
9. Inspect the piston pin area for the following conditions:
^ Scoring (3)
^ Galling caused by improper installation (3)
^ Fit in the connecting rod and piston