a) Check the outer surface.
b) Use a scraper to remove carbon deposits and other carbon deposits from the piston crown.
c) Clean the piston grooves from deposits using a part of the broken ring.
d) Using a soft brush and solvent, thoroughly clean the piston.
Note: Do not use a wire brush.
2. Check the piston and piston rings.
A. Check the clearance between the piston and the cylinder.
a) Using a micrometer, measure the diameter of the piston skirt in the direction perpendicular to the axis of the piston pin, as shown in the figure.
- Distance "L" - 20 mm
Piston diameter:
- nominal size - 92.918 - 92.944 mm
repair size:
- (0.25) — 93.153-93.179 mm
- (0.50) — 93.403 - 93.429 mm
b) Find the difference between the diameters of the piston and the cylinder. Determine the size of the gap.
- Nominal clearance - 0.071 - 0.089 mm
- Maximum gap - 0.15 mm
If the clearance is greater than the maximum, replace all pistons. If necessary, replace the cylinder block.
Note: When replacing pistons, piston rings must also be replaced.
B. Check the piston ring to piston groove end clearance by measuring it with a flat feeler gauge as shown in the figure.
Nominal clearance:
- compression ring No.1 - 0.06 -0.10 mm
- compression ring No.2 - 0.04 - 0.08 mm
- oil scraper ring - 0.02 - 0.06 mm
Maximum gap - 0.15 mm
If the clearance is greater than the permissible limit, replace the piston and piston rings.
B. Check the piston ring gap.
a) Insert the piston ring into the cylinder.
b) Use the piston to push the ring away from the cylinder block surface as shown in the figure.
c) Use a flat feeler gauge to measure the gap in the ring lock.
Nominal clearance:
- compression ring No.1 - 0.22 - 0.32 mm
- compression ring #2 - 0.49 - 0.64 mm
- oil scraper ring - 0.22 - 0.52 mm
Maximum clearance - 1.00 mm
If the gap in the lock is greater than the maximum, replace the piston ring and repeat the check again. If the gap is still greater than the maximum, replace the cylinder block.
3. Check the alignment of the connecting rod heads.
A. Using the special tool and a flat feeler gauge, check the connecting rod bend as shown in the illustration.
- Maximum allowable bending per 50 mm of length is 0.075 m/m
- Maximum permissible twisting per 50 mm of length is 0.18 mm
- Connecting rod length - 162.96 - 163.04 mm
If the bending or twisting is greater than the allowable limit, replace the connecting rod together with the connecting rod cap.
B. Check the distance between the piston pin axis and the connecting rod journal axis.
- Center distance - 162.96-163.03 mm
B. Check the piston pin oil clearance.
a) Using a micrometer, measure the piston pin diameter in the "X" and "Y" directions as shown in the figure.
- Nominal piston pin diameter - 33.994 - 34.000 mm
b) Using a bore gauge, measure the inner diameter of the connecting rod upper head in the "X" and "Y" directions as shown in the figure.
- Nominal diameter - 34.012 - 34.033 mm
c) Determine the oil clearance: subtract the piston pin diameter from the inner diameter of the connecting rod upper head.
- Nominal clearance - 0.012 - 0.039 mm
Replace the connecting rod or piston pin if necessary.
4. Check the piston pin oil clearance and the piston pin holes in the piston boss.
a) Measure the diameter of the piston pin hole in the piston boss.
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- Nominal diameter - 33.997 - 34.007 mm
b) Find the difference between the diameters of the piston pin and the hole for the piston pin.
- Oil clearance - 0.003 - 0.013 mm
Replace piston and/or piston pin if necessary.