Yanmar 6BY2 - Inspect Pistons and Piston Rings

ENGINE
Pistons and Cylinders
5-32 BY Service Manual
© 2009 Yanmar Marine International
11. Remove the wrist pin retaining rings
(Figure 5-48).
Figure 5-48
Figure 5-48
12. Push out the wrist pin. Keep piston and
matched wrist pin together. NOTICE: Pistons
and wrist pins are matched. NEVER mix parts.
13. Use a piston ring expander (Figure 5-49) to
remove the piston rings, taking care not to
scratch the surface of the piston.
Figure 5-49
Figure 5-49
Inspect Pistons and Piston Rings
1. Insert new piston rings, one at a time, into the
cylinder. Use a piston with the piston rings
removed to slide the ring squarely into the
cylinder bore. Measure the end gap of each
piston ring (Figure 5-50).
Figure 5-50
Figure 5-50
Note: Measure cylinder bore to ensure it is
within specifications before measuring
piston ring end gap. See Inspect
Cylinder Block on page 5-62.
Specifications
2. Clean piston ring grooves using a piston ring
groove cleaning tool. Follow tool manufacturer’s
instructions for correct operation.
Inspection Item Standard Limit
Top Piston
Ring
Side
Clearance
0.12 to 0.16 mm
(0.005 to 0.006 in.)
-
End Gap 0.20 to 0.35 mm
(0.008 to 0.014 in.)
-
Second
Piston
Ring
Side
Clearance
0.07 to 0.11 mm
(0.003 to 0.004 in.)
-
End Gap 0.30 to 0.45 mm
(0.012 to 0.018 in.)
-
Oil Ring Side
Clearance
Cannot be measured
End Gap
Piston-to-
Cylinder
Clearance
0.15 mm
(0.006 in.)