Piston Ring: Testing and Inspection
VISUAL INSPECTIONCheck each piston ring for breakage, damage and abnormal wear. Replace the defective rings. When the piston requires replacement, also replace the rings.
SIDE CLEARANCE
Using a suitable feeler gauge, measure the piston ring side clearance, then proceed as follows:
a. If the measured value exceeds the service limit, insert a new ring in a ring groove to measure the side clearance.
b. If the clearance still exceeds the service limit, replace the piston and rings together.
c. If it is less than the service limit, replace only the piston rings.
Piston ring side clearance Standard Value:
No. 1, 0.040-0.085 mm(0.0016-0.0031 inch).
No. 2, 0.040-0.085 mm(0.0016-0.0031 inch).
Piston ring side clearance wear limit:
No. 1, 0.100 mm (0.0040 inch).
No. 2, 0.100 mm (0.0040 inch).
RING END GAP
1. To measure the piston ring end gap, insert a piston ring into the cylinder bore.
2. Position the ring at right angles to the cylinder wall by gently pressing it down with a piston.
3. Measure the gap with a feeler gauge.
4. If the gap exceeds the service limit, replace the piston ring.
Standard Value:
Piston ring end gap No. 1
0.230-0.380 mm (0.0090-0.0149 inch)
Piston ring end gap No. 2
0.450-0.600 mm (0.0177-0.0236 inch)
Oil ring side rail end gap
0.200-0.600 mm (0.0780-0.0236 inch)
Service Limit
Piston ring end gap No. 1
1.000 mm (0.0394 inch)
Piston ring end gap No. 2
1.000 mm (0.0394 inch)
Oil ring side rail end gap
1.000 mm (0.0394 inch)
SERVICE (OVERSIZE) RINGS
1. When replacing the ring without correcting the cylinder bore, check the gap with the ring positioned at the bottom of the ring travel.
2. When replacing a ring, use a ring of the same size.
3. Piston ring service size and mark:
Standard Size;
No Mark
0.25 mm (0.010 in.) O.S;
25
0.50 mm (0.020 in.) O.S;
50
0.75 mm (0.030 in.) O.S;
75
1.00 mm (0.039 in.) O.S;
100
NOTE: The mark can be found on the upper side of the ring next to the end.