To do the job, you will need a bore gauge and a piston ring mandrel.
Disassembly
1. Remove the piston rings from the piston («Piston rings and connecting rod bearings - replacement»).
2. With an awl or a screwdriver with a thin blade, pry off and remove the piston pin lock ring from the groove.
Recommendation. If the grooves of the retaining rings are jammed, in the nicks and the rings in them are not securely fixed, the piston should be replaced.
3. With a soft metal bar with a diameter of 16-18 mm, we push out the piston pin and remove the piston from the connecting rod.
Examination
For new engines, the clearance between the piston and the cylinder is 0.025-0.045 mm and will be set by installing pistons of the same class as the cylinders. The class of the piston and cylinder are indicated by Latin letters, which are knocked out on the lower mating surface of the cylinder block...
...and on the bottom of the piston. The arrow on the piston points towards the front end of the crankshaft.
Comment. For how to use the caliper, see the enclosed instructions or specialist literature.
1. With a bore gauge, we check the wear of the cylinder walls.
Measurements are carried out in four belts (3, 10, 60 and 112 mm from the top edge of the cylinder) in the longitudinal and transverse directions of the engine. In the upper belt, the cylinder does not wear out. By the difference in readings of the caliper in different belts, we determine the degree of wear of each cylinder.
2. Having measured the diameter of the piston skirt with a micrometer, we determine its wear.
Recommendation. Small uniform cylinder wear (within 0.05mm) you can try to compensate by installing a piston of another class with a larger diameter.
If the maximum wear is 0.15 mm or more, it is necessary to bore the cylinders and install oversized pistons.
Selection of pistons and fingers
For new engines, the clearance between the piston and the cylinder is 0.025-0.045 mm and is set by installing pistons of the same class as the cylinder class.
1. With a bore gauge, we check the wear of the cylinder walls (see above).
Cylinder diameters divided into five size classes (see table. 8.1.5). The class of each cylinder is stamped on the lower mating surface of the cylinder block.
Table 8.1.5. Cylinder classes by diameter
Designation | Diameter, mm |
A | 82,00-82,01 |
IN | 82,01-82,02 |
WITH | 82,02-82,03 |
D | 82,03-82,04 |
E | 82,04-82,05 |
Recommendation. Small uniform cylinder wear (within 0.05mm) it is possible to compensate by installing a piston of another class with a larger diameter.
If the maximum wear is 0.15 mm or more, it is necessary to bore the cylinders and install oversized pistons.
Cylinder bore of 0.4 mm and 0.8 mm is provided for the dimensions of the repair pistons.
2. On the bottom of the piston are marked, where:
- 2 - all holes for the piston pin;
- C - piston class;
- ← - arrow for orienting the piston in the cylinder (should point towards the timing drive);
- G - piston mass group.
According to the diameter of the hole for the piston pin, the pistons are divided into ori class (1, 2, 3) - through 0.004 mm.
The outer diameter of the pistons are divided into five classes (A, B, C, D. E) - through 0.01 mm (measured in a plane perpendicular to the piston pin at a distance of 55 mm from the piston crown).
The size of the pistons are nominal and two repair sizes. Nominal size pistons are not marked. Pistons of the first repair size are manufactured with a diameter increased by 0.4 mm and are marked with a symbol «d». Pistons of the second repair size have a diameter increased by 0.8 mm and a symbol with a symbol «□».
On the engine, all pistons must be of the same mass group. Pistons of the nominal group are indicated by the symbol «G». Pistons with an increased and reduced mass of 5 g are indicated «+» * And «—» respectively.
The class of the finger is marked with paint on its end.
According to the outer diameter, the fingers are divided into ori class (blue, green and red), through 0.004 mm.
To facilitate the selection of a finger to the piston bore, the required class of the finger is indicated on its inner side with paint.
The required pin class is indicated on the connecting rod cap 2. The connecting rods are divided into classes according to the mass of the heads. Mamosnoye marking on the connecting rod cap 1...
...or paint.
Warning! Connecting rods of the same weight class must be installed on the engine (see table. 8.1.6).