Connecting Rod: Service and Repair

REPLACEMENT
Refer to the illustration for the service procedure, noting the following points:





1. Mark the cylinder number on the side of the connecting rod big end for correct reassembly.
2. Keep the removed connecting rods, caps, and bearings in order according to the cylinder number.





3. Verifying the mark made during disassembly, install the bearing cap to the connecting rod. If the connecting rod is new with no index mark, make sure that the bearing locking notches come on the same side as shown.





4. Make sure that the connecting rod big end side clearance meets the specification. The standard value is 0.10 - 0.25 mm (0.0039 - 0.0098 inch) and the limit is 0.4 mm (0.016 inch).

NOTE: Installation of the connecting rod nut should be performed with the cylinder head or the spark plug removed.

5. Since the connecting rod bolts and nuts are torqued using the plastic area tightening method, the bolts should be examined before reuse. If the bolt threads are "necked down", the bolt should be replaced.

NOTE: Necking can be checked by running a nut with fingers to the full length of the bolt threads. If the nut does not run down smoothly, the bolt should be replaced.

6. Before installation of each nut, apply engine oil to the threaded portion and bearing surface of the nut.
7. Loosely tighten each nut to the bolt.
8. Then tighten the nuts alternately to a torque of 20 Nm (14.5 ft. lbs.) to install the cap properly.
9. Make a paint mark on the head of each nut.
10. Make a paint mark on the bolt end at the position 90° - 100° from the paint mark made on the nut in the direction of tightening the nut.
11. Give a 90° - 100° turn to the nut and make sure that the paint mark on the nut and that on the bolt are in alignment.

NOTE:
- If the nut is turned less than 90°, proper fastening performance may not be expected. When tightening the nut, therefore, be careful to give a sufficient turn to it.
- If the nut is overtightened (exceeding 100°), loosen the nut completely and then retighten it by repeating the tightening procedure from step 5.