Piston Ring: Testing and Inspection

1. Measure the piston ring side clearance.
- If the measured value exceeds the service limit, insert a new ring in a ring groove to measure the side clearance.
- If the clearance still exceeds the service limit, replace the piston and rings together.
- If it is less than the service limit, replace only the piston rings.
- Piston ring side clearance:
Standard value:
No.1 0.04-0.085 mm (0.0016-0.0031 inch).
No.2 0.04-0.085 mm (0.0016-0.0031 inch).
Limit:
No.1 0.1 mm (0.004 inch).
No.2 0.1 mm (0.004 inch).
2. To measure the piston ring end gap, insert a piston ring into the cylinder bore.
- Position the ring at right angles to the cylinder wall by gently pressing it down with a piston.
- Measure the gap with a feeler gauge.
Standard Value:
Ring Number 1: 0.15-0.30 mm (0.0059-0.0118 inch).
Ring Number 2: 0.25-0.40 mm (0.0080-0.0140 inch).
Oil Ring Side Rail: 0.20-0.70 mm (0.0078-0.0275 inch).
Limit:
Ring Number 1: 1.00 mm (0.0390 inch).
Ring Number 2: 1.00 mm (0.0390 inch).
Oil Ring Side Rail: 1.00 mm (0.0390 inch).
- If the gap exceeds the service limit, replace the piston ring.
- When replacing the ring without correcting the cylinder bore, check the gap with the ring positioned at the bottom of the ring travel.
- When replacing a ring, use a ring of the same size.
- Piston ring service size and mark:
STD: None.
0.25 mm (0.010 inch) O.S: 25.
0.50 mm (0.020 inch) O.S: 50.
0.75 mm (0.030 inch) O.S: 75.
1.00 mm (0.039 inch) O.S: 100.

NOTE: The mark can be found on the upper side of the ring next to the end.