Examination
Piston
1. Check the outer surface of the piston for damage, wear, or uneven wear. If necessary, replace the piston.
2. Check the piston pin by inserting it into the piston bore. The piston pin should smoothly enter the piston when pressed by hand (at room temperature).
Piston rings
1. Check each piston ring for damage and uneven wear. If necessary, replace piston rings.
2. When replacing the piston, the piston rings must also be replaced.
3. Insert a new piston ring into the piston groove and use a feeler gauge to measure the gap between the piston ring and the groove wall. If the clearance exceeds the maximum allowable value, replace the piston.
Gap between piston ring and piston groove:
- Second compression ring: 0.065 - 0.11 mm
- Oil scraper ring: 0.03–0.07
4. Measure the piston ring gap by manually inserting the piston ring into the engine cylinder. Use the piston crown to push the piston ring into the bottom of the cylinder.
5. Use a feeler gauge to measure the clearance in the piston ring lock.
Piston ring clearance:
- First compression ring: 0.2–0.3 mm
- Second compression ring: 0.30-0.45 mm
- Oil scraper ring: 0.20–0.45 mm
- Maximum allowable gap: 0.8 mm
Connecting rod bearing shells
1. Check the working surfaces of the connecting rod bearing shells for streaks, scratches, localized corrosion, wear, and other damage. If necessary, replace the liners. If the working surfaces of the connecting rod bearing shells are severely damaged, check the condition of the crankshaft connecting rod journals. If the crankshaft is also damaged, replace it or regrind the journals to the next reduced size for reuse.
2. Measure the inner diameter of the connecting rod bearing shells and the diameter of the crankshaft journals. If the oil clearance exceeds the allowable limits, replace the liners and, if necessary, the crankshaft.
- Oil clearance in connecting rod bearings: 0.024–0.042 mm
- Maximum allowable gap: 0.10 mm
Installation
Connecting rod, piston pin and piston
1. Connect the piston to the connecting rod.
2. Align the front marks and insert the piston pin. The piston pin should smoothly enter the piston when pressed by hand (at room temperature). If there is too much clearance, replace the piston pin.
Piston rings
1. Install the oil scraper ring expander and oil scraper ring on the piston. Using pliers to expand the piston rings, install the compression ring No. 2, then install the compression ring No. 1. Make sure the marks on the piston rings are facing the piston crown.
2. Position the piston ring locks as shown.
3. Install the piston with piston rings over the first cylinder, with the mark on the piston facing the front of the cylinder block.
4. Use the tool to compress the piston rings on the piston. Using a hammer handle, press the piston into the cylinder so that the lower end of the connecting rod rests on the crankshaft journal.
5. Install the connecting rod bearing into the connecting rod cap. Install the connecting rod cap and secure with nuts. Tightening torque: 25 Nm turn by 90°.
Warning! Do not reuse the connecting rod cap bolts more than three times.
6. With a feeler gauge inserted between the connecting rod and the crankshaft, measure the side clearance of the connecting rod.
- Rated connecting rod side clearance: 0.10 - 0.35 mm
- Maximum allowable gap: 0.40 mm