Piston Rings - Yanmar 3YM30 Service Manual

5.3.3 Piston rings

There are two compression rings and one oil ring.
The absence of an oil ring on the piston skirt prevents
oil from being kept on the thrust surface and in turn
provides good lubrication.
(1) Measuring the rings.
Measure the thickness and width of the rings, and the
ring-to-groove clearance after installation. Replace if
wear exceed the limit.
3YM30
Groove width 1.550-1.570
Top ring Ring width
Clearance
Groove width 1.580-1.595
Second ring Ring width
Clearance
Groove width 3.010-3.030
Oil ring Ring width
Clearance
3YM20/2YM15
Groove width 1.550-1.570
Top ring Ring width
Clearance
Groove width 1.540-1.560
Second ring Ring width
Clearance
Groove width 3.010-3.030
Oil ring Ring width
Clearance
Standard Limit
-
1.470-1.490 1.450
0.060-0.100 -
1.695
1.430-1.450 1.410
0.013-0.165 0.285
3.130
2.970-2.990 2.950
0.020-0.060 0.180
Standard Limit
-
1.470-1.490 1.450
0.060-0.100 -
1.660
1.470-1.490 1.450
0.050-0.090 0.210
3.130
2.970-3.010 2.950
0.020-0.060 0.180
118R1
5. Inspection and servicing of basic engine parts
(Ring components)
mm
(Measuring side clearance)
mm
Top ring
Second ring
Oil ring
Width
Thickness