Piston and Connecting Rod

PISTON AND CONNECTING ROD





Removal
Follow removal steps outlined in illustration.

Removal Service Points





A. Connecting Rod Cap Removal.
Mark the large end of the connecting rod with the cylinder number for further reassembly.





B. Piston Rings Removal.
Use a piston expander to remove the piston rings.

Inspection





Piston Ring
1. Check for the clearance between the piston ring and ring groove. If the limit is exceeded, replace the ring or piston, or both.

Standard value:
No. 1 ring 0.04 - 0.08 mm (0.0016 - 0.0031 inch)
No. 2 ring 0.02 - 0.06 mm (0.0008 - 0.0024 Inch)
Limit:
0.1 mm (0.004 inch)





2. Install the piston ring into the cylinder bore. Force it down with a piston, its crown being in contact with the ring, to correctly position it at right angles to the cylinder wall. Then, measure the end gap with a feeler gauge. If the ring gap exceeds the limit, replace the piston ring.





Crankshaft Pin Oil Clearance (plastigage Method)
1. Remove oil from crankshaft pin and connecting rod bearing.
2. Cut the Plastigage to the same length as the width of bearing and place it on crankshaft pin in parallel with its axis.





3. Install the connecting rod cap carefully and tighten the nuts to specified torque.
4. Carefully remove the connecting rod cap.
5. Measure the width of the Plastigage at its widest part by using a scale printed on the Plastigage package.

Installation
Installation in reverse order as removal.

Installation Service Points








A. Oil Ring Installation.
1. Fit the oil ring spacer into the piston ring groove.

NOTE:
1. The side rails and spacer may be installed in either direction.
2. New spacers and side rails are colored for identification of their sizes.

Size: Identification color
Standard: None
0.50 mm oversize: Blue
1.00 mm oversize: Yellow

2. Install the upper side rail. To install the side rail, first fit one end of the rail into the piston groove, then press the remaining portion into position by finger. See illustration.

NOTE: Do not use piston ring expander when installing side rail. Otherwise, the side rail will be broken.
3. Install the lower side rail in the same procedure as described in step (2).
4. Check that the side rails move smoothly in either direction.





B. Piston Rings Installation.
Use a piston ring expander to fit the No. 2 and then No. 1 piston ring into position.





NOTE:
1. The ring end has the identification mark.

Identification mark
No. 1 ring: 1R
No. 2 ring: 2R

2. Install piston rings to the piston crown side with identification mark facing up.
3. Size marks on piston rings are as follows.

Size mark
Standard: NONE
0.50 mm oversize: 50
1.00 mm oversize: 100





C. Piston And Connecting Rod Assembly Installation.
1. Coat a large amount of engine oil on the circumference of the piston, piston ring, and oil ring.
2. Arrange the piston ring and oil ring gaps (side rail and spacer) as shown in the figure.
3. Rotate crankshaft so that crank pin is on center of cylinder bore.





4. Use suitable thread protectors on connecting rod bolts before inserting piston and connecting rod assembly into cylinder block. Do not nick crank pin.
5. Use a suitable piston ring compressor tool to install piston and connecting rod assembly into cylinder block.

CAUTION: Insert the front mark (arrow) on the top of the piston so it faces the engine front (timing belt side).





D. Connecting Rod Bearing Installation.
When replacing the bearing, choose a bearing as follows.
1. Measure the diameter of the crankshaft pin and then understand which class the pin belongs to in the following table.
In addition, a service part has its own identification color as shown in the figure.











2. The figure shows an identification mark of a connecting rod bearing.
3. Choose a bearing according to the above table.

[Example]
If the measured value of a crankshaft pin outer diameter is between 44.995 and 45.000 mm (1.7715 and 1.7717 inch), the pin is classified as "A" in the table.
In case the crankshaft is also replaced by a spare part, check the identification colors of the pins painted on the new crankshaft. For example, if the color is yellow, the pin is classified as "A".
In the above cases, select the connecting rod bearing having identification mark"1".





E. Connecting Rod Cap Installation.
1. Mate the correct bearing cap with the correct connecting rod by checking with the alignment marks marked during disassembly. If a new connecting rod is used which has no alignment mark, position the notches for locking the bearing on the same side.





2. Check if the thrust clearance in the connecting rod big end is correct.

F. Connecting Rod Cap Nut Installation.

NOTE: Remove the cylinder head or spark plug to loosen the connecting rod nuts.

1. Since the connecting rod bolts and nuts are torqued using a new procedure, examine them BEFORE reuse. If the bolt threads are "necked down", replace the bolts.
Necking can be checked by running a nut with fingers to the full length of the bolt's thread. If the nut does not run down smoothly, replace the bolt.





2. Before installing the nuts, the threads should be oiled with engine oil.
3. Install both nuts on each bolt finger tight, then alternately torque each nut to assemble the cap properly.

4. Tighten the nuts to 20 Nm (14.5 ft. lbs.).
5. Paint a mark on the nut head.
6. Use the painted mark as a reference to paint a mark on the bolt in a position 90° - 100° in the tightening direction of the nut.
7. Tighten the nuts 90° - 100° and then check that the painted mark on the nuts is aligned with that on the bolts.

CAUTION:
1. If the tightening angle is less than 90°, the bolt will be loosened. Be careful to observe the tightening angle.
2. If the tightening angle is more than 100°, remove the nut and repeat the procedure from step (1).