Spark

Piston, Connecting Rod, and Bearing Cleaning and Inspection

Note: DO NOT use a wire brush any part of the piston.

1. Clean the piston skirts and the pins with a cleaning solvent.
2. Clean the piston ring grooves with a groove cleaner. Ensure that the oil ring holes and slots are clean.

Warning: Refer to Safety Glasses and Compressed Air Warning in the Preface section.

3. Dry the piston with compressed air.

1. Inspect the pistons for the following conditions:

•	Ring grooves for nicks, burrs that may cause binding (5)

•	Warped or worn ring lands (5)

•	Piston pin retainer grooves for burrs (2)

•	Eroded areas at the top of the piston (1)

•	Scuffed or damaged skirt coating (4)

•	Worn piston pin bores or worn piston pins (3)

2. Replace pistons that show any signs of damage or wear above acceptable tolerances.

1. Measure piston width using the following procedure:

1.1.	Using an outside micrometer, measure the width of the piston at 30 mm (1.181 in) below the crown, top (1), at the thrust surfaces of the piston, perpendicular to the piston pin centreline.

1.2.	Compare your results with the engine mechanical specifications. Refer to Engine Mechanical Specifications

1.3.	If the clearance obtained through measurement is greater than the provided specifications and the cylinder bores are within specification, replace the piston.




2. Measure the gudgeon pin bore to gudgeon pin (2) clearances using the following procedure:

2.1.	Piston pin bores and pins must be free of varnish or scuffing.

2.2.	Use an outside micrometer (1) to measure the gudgeon pin in the piston contact areas.

1. Measure the piston ring (1) side clearance using the following procedure:

1.1.	Roll the piston ring (1) entirely around the piston ring groove. If any binding is caused by the ring groove, dress the groove with a fine file. If any binding is caused by a distorted piston ring (1), replace the piston ring (1).

1.2.	With the piston ring (1) on the piston, use feeler gauges (2) to check clearance at multiple locations.

1.3.	Compare the measurements with piston ring side clearance listed in the.

1.4.	If the clearance is greater than specifications, replace the piston ring (1).




2. There is a locating marking 'R' (1) on the compression rings near the end for identification. Install the compression rings with the dimple facing up.
3. If the new ring does not reduce the clearance to the correct specification, install a new piston.
4. If the new piston does not meet clearance specifications, the cylinder block may need to be oversized to 0.25 mm (0.010 in). There is only one size of oversized pistons and rings available for service.

1. Clean the connecting rods in solvent.

Warning: Refer to Safety Glasses and Compressed Air Warning in the Preface section.

2. Dry the connecting rod using compressed air.

1. Inspect the piston pin bushing (4) for scoring or damage.
2. Inspect the connecting rod beam (1) for twisting or bending.
3. Inspect the rod cap (2) for any nicks or damage caused by possible interference.
4. Inspect for scratches or abrasion on the rod bearing seating surface.

Note: DO NOT scrape the rod or rod cap.

5. If the connecting rod bores contain minor scratches or abrasions, clean the bores in a circular direction with a light emery paper.
6. Inspect the connecting rod bolts (3) for damage or stretching.

1. Using an inside micrometer, measure the connecting rod gudgeon pin bore (1).
2. Subtract the piston pin diameter from the piston pin bore (1).
3. Compare the clearance measurements with the.
4. If the clearance is above acceptable tolerances, replace the piston pin. If a new pin does not resolve the clearance condition, replace the connecting rod.



5. Using an inside micrometer, measure the connecting rod crankshaft bearing bore (1).
6. Compare the bore measurements with the.
7. Replace the connecting rod if the connecting rod crankshaft bearing bore (1) is out of specifications. DO NOT recondition the connecting rod.

1. Cut the plastic gauge (1) the same length as the bearing width and put it on the crankshaft bearing. It should be parallel with the crankshaft.

Caution: Refer to Fastener Caution in the Preface section.

2. Install the big end bearing and caps, tighten to 33 N·m (24 lb ft).
3. Remove the connecting rod cap and bearing.



4. Determine the big end bearing clearance by comparing the width of the flattened plastic gauging material (1) at its widest point with the graduation on the gauging material container (2).
5. Compare your measurements with the engine mechanical specifications. Refer to Engine Mechanical Specifications . If the new bearings DO NOT provide the proper crankshaft to big end bearing clearance, inspect the following: Engine Mechanical Specifications .
6. Clean the plastic gaging material from the connecting rod bearing journals using a soft lint-free cloth.