Piston: Service and Repair
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.
3. Remove the stop screw from the base.
4. Select the correct piston support for your application. Fit the piston support onto the base. Place the base on press support blocks.
5. Insert the press pin through the piston pin hole. Select the correct connecting rod guide pin. Thread the guide pin onto the threaded portion of the press pin.
6. Position the piston assembly on the piston support in the press. With the press pin up, insert the guide pin through the hole in the piston and through the hole in the piston support.
7. Press the piston pin out of the assembly.
CAUTION:
- To avoid piston damage the piston support must seat squarely against the piston.
- Verify that the piston pin will slide through the hole in the piston support.
8. Remove the piston pin from the press pin.
INSTALLATION
Reverse the removal procedure to install, noting the following:
1. Thread the stop screw and lock nut assembly into the base. Fit the correct piston support on 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 markings on the press pin, adjust the stop screw to the depth as shown. Regarding proper 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.
NOTE: 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.
9. Fit the oil ring spacer into the piston ring groove.
NOTE:
- The side rails and spacer may be installed in either direction
- New spacers and side rails are colored for identification of their sizes.
Standard: not colored
0.50 mm oversize: blue
1.00 mm oversize: yellow
10. 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 with a finger (see illustration).
CAUTION: Use of a ring expander to expand the side rail end gap can break the side rail, unlike other piston rings. Do not use a piston ring expander when installing side rail.
11. Install the lower side rail using the same procedure.
12. Make sure that the side rails move smoothly in either direction.
13. Using piston ring expander, fit No. 2 and then No. 1 piston ring into position. The ring end is provided with identification mark. Identification mark for the No. 1 ring is "1R" and No. 2 ring is marked with "2R".
14. Install piston rings with identification mark facing up, to the piston crown side.
15. Size marks on piston rings are as follows:
Size and size mark
Standard: NONE
0.50 mm oversize: 50
1.00 mm oversize: 100
16. Install the piston and connecting rod as follows:
17. Liberally coat engine oil on the circumference of the piston, piston ring, and oil ring.
18. Arrange the piston ring and oil ring gaps (side rail and spacer) as shown. The identification mark is 63DTF.
19. Rotate the crankshaft so that crank pin is on center of the cylinder bore.
20. Use suitable thread protectors on the connecting rod bolts before inserting piston and connecting rod assembly into the cylinder block.
CAUTION: Care must be taken not to nick the crank pin.
21. Using a suitable piston ring compressor tool, install the piston and connecting rod assembly into the cylinder block.
22. When the connecting rod bearings need replacing, select and install a proper bearing by the following procedure:
23. Measure the crankshaft pin diameter and confirm its classification from the table. In the case of a crankshaft supplied as a service part, identification colors of its pins are painted at the positions shown.
24. The connecting rod bearing identification mark is stamped at the position shown in the illustration. Connecting rod I.D. is 48.000 - 48.015 mm (1.8900 - 1.8904 inch).
25. Select a proper bearing from the table on the basis of the identification data confirmed under steps 23 and 24.
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 "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".
26. 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.
27. 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.
28. 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.
29. Before installation of each nut, apply engine oil to the threaded portion and bearing surface of the nut.
30. Loosely tighten each nut to the bolt.
31. Then tighten the nuts alternately to a torque of 20 Nm (14.5 ft. lbs.) to install the cap properly.
32. Make a paint mark on the head of each nut.
33. 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.
34. 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 28.