Piston and Connecting Rod
PISTON AND CONNECTING RODREMOVAL AND INSTALLATION
Removal Steps 1-12:
REMOVAL SERVICE POINTS
A CONNECTING ROD CAP REMOVAL
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.
B PISTON PIN REMOVAL
1. Remove the stop screw from the base.
2. Select the correct piston support for your application (See above). Fit the piston support onto the base. Place the base on press support blocks.
3. Insert the press pin through the piston pin hole. Select the correct connecting rod guide pin (See above). Thread the guide pin onto the threaded portion of the press pin.
4. Position the piston assembly on the piston support in the press. With the press pin up as shown in the illustration, insert the guide pin through the hole in the piston and through the hole in the piston support.
5. Press the piston pin out of the assembly.
IMPORTANT: To avoid piston damage,
1. The piston support must seat squarely against the piston.
2. Verify that the piston pin will slide through the hole in the piston support.
6. Remove the piston pin from the press pin.
INSPECTION
PISTON
1. Replace the piston if scratches or seizure is evident on its surfaces (especially the thrust surface). Replace the piston if it is cracked.
PISTON PIN
1. Insert the piston pin into the piston pin hole with a thumb. You should feel a slight resistance. Replace the piston pin if it can be easily inserted or there is an excessive play.
2. The piston and piston pin must be replaced as an assembly.
PISTON RING
1. Check the piston ring for damage, excessive wear, and breakage and replace if defects are evident. If the piston has been replaced with a new one, the piston rings must also be replaced with new ones.
2. Check for the clearance between the piston ring and ring groove. If the limit is exceeded, replace the ring or piston, or both.
3. 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 is excessive, replace the piston ring.
CRANKSHAFT PIN OIL CLEARANCE [PLASTIC GAUGE METHOD]
1. Remove oil from crankshaft pin and connecting rod bearing.
2. Cut the plastic gauge 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 bolts to the specified torque.
4. Carefully remove the connecting rod cap.
5. Measure the width of the plastic gauge at its widest part by using a scale printed on the plastic gauge package.
Standard value: 0.02-0.05 mm (0.0008-0.0020 in.)
Limit: 0.1 mm (0.004 in.)
INSTALLATION SERVICE POINTS
A PISTON PIN INSTALLATION
1. Thread the stop screw and lock nut assembly into the base. Fit the correct piston support on the top of the base. Insert the press pin, threaded end up, into the hole in the piston support until the press pin touches the stop screw.(2) Using the graduations on the press pin, adjust the stop screw to the depth shown below.
2. Using the graduations on the press pin, adjust the stop screw to the depth shown below.
Depth: Refer to the operating instructions on the special tool.
3. Place the base on press support blocks.
4. Slide the piston pin over the threaded end of the press pin, and thread the correct guide pin up against it.
5. Coat the piston pin with oil, and with the connecting rod held in position, slide the guide pin through the piston and connecting rod.
6. Press the piston pin through the connecting rod until the guide pin contacts the stop screw.
7. Remove the piston assembly from the base. Remove the guide pin and press pin from the assembly.
IMPORTANT: Due to production tolerance variations, it is necessary to visually inspect the piston pin depth after installation to verify that the piston pin is centered. Adjust if necessary.
8. Check that the piston moves smoothly.
B 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.
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.
Use of ring expander to expand the side rail end gap can break the side rail, unlike other piston rings.
CAUTION: Do not use piston ring expander when installing side rail.
3. Install the lower side rail in the same procedure as described in step (2).
4. Make sure that the side rails move smoothly in either direction.
C PISTON RING NO.2 / PISTON RING NO.1 INSTALLATION
1. Using a position ring expander, fit No.2 and then No.1 piston ring into position.
NOTE: The ring end is provided with identification mark as follows
2. Install piston rings with identification mark facing up, to the piston crown side.
3. Piston rings have one of the following size marks stamped according to their size.
D PISTON AND CONNECTING ROD INSTALLATION
1. Liberally coat 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 the crankshaft so that the crank pin is on the center of the cylinder bore.
4. Use suitable thread protectors on the connecting rod bolts before inserting the piston and connecting rod assembly into the cylinder block. Care must be taken not to nick the crank pin.
5. Using a suitable piston ring compressor tool, install the piston and connecting rod assembly into the cylinder block.
E CONNECTING ROD BEARING INSTALLATION
When the bearing needs replaceing, select and install a proper bearing by the following procedure.
1. Measure the crankshaft pin diameter and confirm its classification from the following table. In the case of the crankshaft are painted at the positions shown in the illustration.
2. The connecting rod bearing identification mark is stamped at the position shown in the illustration.
3. Loosely tighten each nut to the bolt.
[Example]
1. If the measured value of a crankshaft pin outer diameter is between 44.995 and 45.000 mm (1.7715 and 1.7717.in.), the pin is classified as "1" 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. If the color is yellow, for example, the pin is classified as "1". In the above cases, select the connecting rod bearing having identification mark "1".
F CONNECTING ROD CAP INSTALLATION
1. 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.
2. Make sure that the connecting rod big end side clearance meets the specification.
Standard value: 0.10-0.25 mm (0.0039-0.0098 in.)
Limit: 0.4 mm (0.016 in.)
G CONNECTING ROD CAP NUT INSTALLATION
NOTE: Installation of the connecting rod nut should be performed with the cylinder head or the spark plug removed.
1. 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 boll should be replaced.
Necking can be checked by running a nut with fingers to the full length of the bolt threads. It the nut does not run down smoothly, the bolt should be replaced.
2. Before installation of each nut, apply engine oil to the threaded portion and bearing surface of the nut.
3. Loosely tighten each nut to the bolt.
4. Then tighten the nuts alternately to a torque of 20 Nm (14.5 ft.lbs.) to install the cap properly.
5. Make a paint mark on the head of each nut.
6. Make a paint mark on the bolt end at the position 90° to 100° from the paint mark made on the nut in the direction of tightening the nut.
7. Give a 90° to 100° turn to the nut and make sure that the paint mark on the nut and that on the bolt are in alignment.
Caution:
1. 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.
2. If the nut has been overtightened (exceeding 100°), loosen the nut completely and then retighten it by repeating the tightening procedure from step (1).