22.5B Keep the piston and rod (a), big-end cap (b) and cap nuts (c) together as an assembly
pressing them into place (see illustrations).
7 Remove the pistons from the connecting rods (see Section 23).
Inspection
Check the connecting rods for cracks and other obvious damage. Check that the oil hole in the connecting rod big-end is clear (see illustration).
Apply clean engine oil to the piston pin, insert it into the connecting rod small-end and check for any freeplay between the two (see illustration). Measure the pin external diameter and the small-end bore diameter, then calculate the difference to obtain the small-end-to-piston pin clearance (see illustrations). Compare the result to the
22.6b ... before pressing the bolt into place
22.8 Ensure oil hole (arrowed) is clear
22.9b Measunr
the pin ...
al diameter of
22.9c
. and the internal diameter of the small-end
2*38 Engine, clutch and transmission
22.13 Make sure the tab (A) locates in the notch (B)
22.20a Crankpin journal size code (arrowed)
22.20b Connecting rod size code (arrowed)
Connecting rod code |
Crankpin code |
||
A - (35.994 to 36.000 mm) |
B - (35.988 to 35.994 mm) |
C - (35.982 to 35.988 mm) |
|
1 - (39.000 to 39.006 mm) |
Yellow |
Green |
Brown |
2-(39.006 to 39.012 mm) |
Green |
Brown |
Black |
3-(39.012 to 39.018 mm) |
Brown |
Black |
Blue |
Refer to Section 21 and examine the connecting rod bearing shells. If they are scored, badly scuffed or appear to have seized, new shells must be installed. Always renew 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.
Have the rods checked by a Honda dealer if you are in doubt about their straightness.
Oil clearance check
22.21 Bearing shell colour code location (arrowed)
The connecting rod bearing oil clearance should be checked before the engine is reassembled, even if the bearing shells and the crankpin journals show no apparent sign of wear. Bearing oil clearance is measured with a product called Plastigauge.
Clean the backs of the bearing shells, the bearing locations in both the connecting rod and cap, and the crankpin journals with a suitable solvent or brake system cleaner.
Press the bearing shells into their locations, ensuring that the tab on each shell engages the notch in the connecting rod/cap (see illustration). Clean the bearing surfaces with solvent, taking care not to touch any bearing surface with your fingers.
Cut an appropriate size length of Plastigauge (it should be slightly shorter than the width of the crankpin). Place a strand of Plastigauge on a cleaned crankpin journal. Do not place Plastigauge over the oil holes in the crankpins. Fit the cleaned connecting rod, shells and cap. Make sure the cap is fitted the correct way round so the previously made markings align and that the rod is facing the right way (see Step 3). Tighten the cap nuts evenly, in two or three stages, to the torque setting specified at the beginning of this Chapter, whilst ensuring that the connecting rod does not rotate on the crankshaft. Slacken the cap nuts and remove the connecting rod, again taking great care not to rotate the crankshaft.
Compare the width of the crushed Plastigauge on the crankpin journal to the scale printed on the Plastigauge envelope to obtain the connecting rod bearing oil clearance (see illustration 25.17). Compare the reading to the specifications at the beginning of this Chapter. If the oil clearance falls within the specified range and the bearings are in perfect condition, they can be reused.
Carefully clean away all traces of the Plastigauge from the crankpin journal and bearing shells using a fingernail or other object which will not score the bearing surfaces.
If the clearance is beyond the service limit, measure the diameter of the crankpin journal with a micrometer and compare the result with the appropriate figure in the table
for connecting rod bearing shell selection. For example, if the journal being measured is code B, the table indicates that the service limit for that journal is 35.988 mm. If the journal diameter is larger than the service limit, new bearing shells can be fitted (see Steps 20 and 21). If the journal diameter is smaller than the service limit, the crankshaft should be renewed, although seek the advice of a Honda dealer or engineer to explore all alternatives.
Repeat the oil clearance check for the remaining connecting rod. Always renew all of the shells (on both connecting rods) at the same time.
Install the new shells and check the oil clearance once again.
Bearing shell selection
New bearing shells for the connecting rods are supplied on a selected fit basis. Code letters and numbers marked on the crankshaft webs and the connecting rods are used to identify the correct new bearings. The crankpin journal size codes are marked on the inner crankshaft webs and are either an A, B or C (see illustration). The connecting rod size code is marked on the flat face of the connecting rod and cap and will be either a 1, 2 or 3 (see illustration).
A corresponding range of bearing shells is available. To select the correct shells for a particular big-end, using the table below cross-refer the crankpin journal code letter with the connecting rod code number to determine the colour code of the shells required. For example, if the connecting rod size is 2, and the crankpin size is A, then the bearing shells required are Green. The colour is marked on the side of the shells (see illustration).
Engine, clutch and transmission 2*39
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