Removal
1. Remove the crankshaft (see Section 27).
2. Before removing the rods from the crankshaft. measure the side clearance on each rod with a feeler gauge (see illustration). If the clearance on any rod is greater than the service limit listed in this Chapter's Specifications, that rod will have to be replaced with a new one.
28.2. Measure the connecting rod side clearance
3. Using paint or a felt marker pen. mark the relevant cylinder identity on each connecting rod. Mark across the cap-to-connecting rod join to ensure that the cap is fitted the correct way around on reassembly. Do not obscure the existing markings on one of the connecting rod faces (mark the cylinder ID on the other side) - the number already marked is the connecting rod big-end size code, and the letter is the rod's weight code (see illustration).
28.3. Note the rod's size and weight code markings (arrowed)
4. Unscrew the big-end cap nuts and separate the connecting rod, cap and both bearing shells from the crankpin (see illustrations). Keep the rod, cap, nuts and (if they are to be re-used) the bearing shells together In their correct positions to ensure correct installation.
28.4a. Unscrew the connecting rod big end cap nuts (arrowed)...
28.4b ...and separate the rod from the shaft
Inspection
5. Check the connecting rods for cracks and other obvious damage.
6. If not already done (see Section 16), apply clean engine oil to the piston pin, insert it into the connecting rod small-end and check for any freeplay between the two. Measure the pin OD (see illustration 16.12b) and the smallend bore ID and compare the measurements to the specifications at the beginning of the Chapter (see illustration). Calculate the difference between the measurements taken to obtain the piston pin-to-small end clearance and compare the result to the specifications. Replace components that are worn beyond the specified limits.
28.6. Measure the connecting rod small end internal diameter
7. Refer to Section 26 and examine the connecting rod bearing shells. If they are scored, badly scuffed or appear to have seized, new shells must be installed. Always replace the shells in the connecting rods as a set. If they are badly damaged, check the corresponding crankpin. Evidence of extreme heat, such as discoloration, indicates that lubrication failure has occurred. Be sure to thoroughly check the oil pump and pressure relief valve as well as all oil holes and passages before reassembling the engine.
8. Have the rods checked for twist and bend by a Honda dealer if you are in doubt about their straightness.
Oil clearance check
9. Whether new bearing shells are being fitted or the original ones are being re-used, the connecting rod bearing oil clearance should be checked prior to reassembly.
10. Remove the bearing shells from the connecting rod and cap (see illustration). Clean the backs of the shells and the bearing locations in both the rod and cap.
28.10. Remove the shells from the rod and cap
11. Press the bearing shells into their locations, ensuring that the tab on each shell engages the notch in the connecting rod/cap (see illustrations). Make sure the bearings are fitted in the correct locations and take care not to touch any shell's bearing surface with your fingers.
28.11a. Fit the shell into its housing...
28.11b ...making sure the tab locates in the notch
12. Cut two lengths of the appropriate size Plastigauge (they should be slightly shorter than the width of the crankpin). Place a strand of Plastigauge on each (cleaned) crankpin journal and fit the (clean) connecting rod assemblies, shells and caps (see illustration 28.4b). Make sure the cap is fitted the correct way around so the previously made markings align, and tighten the bearing cap nuts evenly and a little at a time to the torque setting specified at the beginning of the Chapter whilst ensuring that the connecting rod does not rotate (see illustration 28.20a and b). Slacken the cap nuts and remove the connecting rod assemblies, again taking great care not to rotate the crankshaft.
13. Compare the width of the crushed Plastigauge on each crankpin to the scale printed on the Plastigauge envelope to obtain the connecting rod bearing oil clearance.
14. If the clearance is not within the specified limits, the bearing shells may be the wrong grade (or excessively worn if the original shells are being re-used). Before deciding that different grade shells are needed, make sure that no dirt or oil was trapped between the bearing shells and the connecting rod or cap when the clearance was measured. If the clearance is excessive, even with new shells (of the correct size), measure the diameter of the crankpin and compare it to the specifications (see illustration). If it is worn, the crankshaft should be replaced with a new one.
28.14. Measure the diameter of the crankpin to see if it is worn
15. On completion carefully scrape away all traces of the Plastigauge material from the crankpin and bearing shells using a fingernail or other object which is unlikely to score the shells.
Bearing shell selection
16. Replacement bearing shells for the bigend bearings are supplied on a selected fit basis. Codes stamped on the crankshaft and rod are used to identify the correct replacement bearings. The crankpin journal size number Is stamped on the crankshaft middle web adjacent to the crankpin and will be either an A or a B (see illustration 24.12a). The connecting rod size code is marked on the flat face of the connecting rod and cap and will be either a 1 or a 2 (see illustration 28.3).
17. A range of bearing shells is available. Select the correct bearing shells for a particular connecting rod in accordance with the table below. The bearings themselves are identified by a letter and a corresponding colour (see table below). The dimensions relating to the particular codes are given in the specifications at the beginning of the Chapter.
Connecting rod selection
18. It a connecting rod needs to be replaced, the weight of the replacement rod needs to be matched to the other rod being re-used. If both rods are being replaced, they need to be matched together. The connecting rod weight code is marked on the flat face of the connecting rod and cap and will be either an A. B. C or a D (see illustration 28.3). Ideally each rod should have the same weight code as the other, but it is acceptable to be one letter different, e.g. A and B coded rods could be used together, but not A and C coded rods.
Installation
19. Clean the backs of the bearing shells and the bearing housings in both cap and rod. If new shells are being fitted, ensure that all traces of the protective grease are cleaned off using paraffin (kerosene). Wipe the shells, cap and rod dry with a clean lint free cloth. Fit the bearing shells in the connecting rods and caps, making sure the tab on each shell engages the notch in the connecting rod/cap (see illustrations 28.10,11a and b). Lubricate the shells with molybdenum disulphide oil (a 50/50 mixture of molybdenum disulphide grease and clean engine oil). Fit the connecting rod onto the crankpin and fit the cap onto the rod (see illustration 28.4b). Make sure the cap is fitted the correct way around so the previously made markings align. Check to make sure that all components have been returned to their original locations using the marks made on disassembly.
20. Apply some clean oil to the threads and under the heads of the connecting rod nuts; if new rods are being fitted they should come supplied with new bolts and nuts. Fit the nuts and tighten them evenly and a little at a time to the torque setting specified at the beginning of the Chapter (see illustrations).
28.20a. Lubricate the nuts as described...
28.20b ...and tighten them to the specified torque setting
21. Check that the rods rotate smoothly and freely on the crankpin. If there are any signs of roughness or tightness, remove the rods and re-check the bearing clearance.
22. Install the crankshaft (see Section 27).