Connecting Rod: Service and Repair

Disassembly





1. Apply engine oil to the piston pin snap rings (A) and turn them in the ring grooves until the end gaps are lined up with the cutouts in the piston pin bores (B).

NOTE: Take care not to damage the ring grooves.





2. Remove both snap rings (A). Start at the cutout in the piston pin bore. Remove the snap rings carefully so they do not go flying or get lost. Wear eye protection.





3. Heat the piston and connecting rod assembly to about 158°F (70°C) then remove the piston pin.

Inspection

NOTE: Inspect the piston, piston pin and connecting rod when they are at room temperature.





1. Measure the diameter of the piston pin.





2. Zero the dial indicator to the piston pin diameter.





3. Check the difference between the piston pin diameter and piston pin hole diameter in the piston.





4. Measure the piston pin-to-connecting rod clearance.

Reassembly





1. Install a piston pin snap ring (A).
2. Coat the piston pin bore in the piston, the bore in the connecting rod, and the piston pin with engine oil.





3. Heat the piston to about 158°F (70°C).





4. Install the piston pin (A). Assemble the piston (B) and connecting rod (C) with the embossed marks (D) on the same side.
5. Install the remaining snap ring.

Piston Ring Replacement
1. Remove the piston from the cylinder block.





2. Using a piston, push a new ring (A) into the cylinder bore 15 - 20 mm (0.6 - 0.8 inch) from the bottom.
3. Measure the piston ring end-gap (B) with a feeler gauge:
^ If the gap is too small, check to see if you have the proper rings for your engine.
^ If the gap is too large, recheck the cylinder bore diameter against the wear limits. If the bore is over the service limit, the cylinder block must be rebored.
Piston Ring End-Gap:
Top Ring
Standard (New): 0.20 - 0.35 mm (0.008-0.014 inch)
Service Limit: 0.60 mm (0.024 inch)
Second Ring
Standard (New): 0.40 - 0.55 mm (0.016 - 0.022 inch)
Service Limit: 0.70 mm (0.028 inch)
Oil Ring
Standard (New): 0.20 - 0.70 mm (0.008 - 0.028 inch)
Service Limit: 0.80 mm (0.031 inch)





4. Using a ring expander (A), remove the old piston rings (B).
5. Clean all ring grooves thoroughly with a squared off broken ring or ring groove cleaner with a blade to fit the piston grooves. The top and second ring grooves are 1.2 mm (0.05 inch) wide. The oil ring groove is 2.8 mm (0.11 inch) wide. File down a blade if necessary. Do not use a wire brush to clean the ring grooves, or cut the ring grooves deeper with cleaning tools.

NOTE: If the piston is to be separated from the connecting rod, do not install new rings yet.





6. Install the rings as shown. The top ring (A) has a 1B mark and the second ring (B) has a 2B mark. The manufacturing marks (c) must he facing forward.
7. Rotate the rings in their grooves to make sure they do not bind.





8. Position the ring end gaps as shown.





9. After installing a new set of rings, measure the ring-to-groove clearances:

Piston Installation
If the crankshaft is already installed
1. Set the crankshaft to BDC for each cylinder.
2. Remove the connecting rod caps, then install the ring compressor, and check that the bearing is securely in place.





3. Position the arrow (A) and the mark (B) facing the timing belt side of the engine.





4. Position the piston in the cylinder, and tap it in using the wooden handle of a hammer (A). Maintain downward force on the ring compressor (B) to prevent the rings from expanding before entering the cylinder bore.
5. Stop after the ring compressor pops free, and check the connecting rod-to-crank journal alignment before pushing the piston into place.
6. Check the connecting rod bearing clearance with plastigage.
7. Apply engine oil to the bolt threads, then install the rod caps with bearings. Torque the bolts to 20 Nm (2.0 kgf-m, 14 ft. lbs.).





8. Mark the connecting rod (A) and bolt head (B) as shown.
9. Tighten the bolt until the mark on the bolt head lines up with the mark on the connecting rod (turn the bolt 90°)

If the crankshaft is not installed
1. Remove the connecting rod caps, then install the ring compressor, and check that the bearing is securely in place.





2. Position the arrow (A) and the mark (B) facing the timing belt side of the engine.





3. Position the piston in the cylinder, and tap it in using the wooden handle of a hammer (A). Maintain downward force on the ring compressor (B) to prevent the rings from expanding before entering the cylinder bore.
4. Position all pistons at top dead center.

Connecting Rod Bolt Inspection





1. Measure the diameter of each connecting rod bolt at point A and point B.
2. Calculate the difference in diameter between point A and point B.
Point A-Point B = Difference in Diameter
Difference in Diameter:
Specification: 0 - 0.1 mm (0 - 0.004 inch)
3. If the difference in diameter is out of tolerance, replace the connecting rod bolt.