Yanmar 6LY3 series, Service Manual

Page: 103 / 390

ENGINE Inspecting the Cylinder Block and Components
12/05
6LY3 Service Manual
5-37
© 2007 Yanmar Marine International
Measuring the Pistons
Remove carbon deposits from the piston, taking
care not to scratch the piston surface. Check the
combustion surface for any damage.
Measure the outside diameter at the top of the
piston.
• Replace the piston if the outsides of the piston or
ring grooves are worn.
• Measure the outside diameter of the piston at a
right angle from the piston pin as shown in
Figure 5-38
.
If the piston outside diameter exceeds the limit,
replace the piston.
Figure 5-38
Figure 5-38
1 – Piston Skirt
Matching Pistons to Cylinder Sleeves
Pistons must be matched to cylinder sleeves according to the table below. The size mark of a piston is
shown on its top surface. The size mark of a cylinder sleeve is shown on the non-operating side of the
cylinder block. The serviceable matches of pistons and sleeves are as provided below.
Piston Outside Diameter
Piston
ID
Mark
Standard Limit
Clearance
Between
Piston and
Cylinder
L
105.799-105.809 mm
(4.1653-4.1656 in.)
105.780
mm
(4.1645
in.)
0.111-0.131 mm
(0.0043-0.0051
in.)
ML 105.794-105.799 mm
(4.1651-4.1653 in.)
MS 105.789-105.794 mm
(4.1649-4.1651 in.)
S
105.779-105.789 mm
(4.1645-4.1649 in.)
0005621
22 mm
(0.9 in.)
(1)
Piston Outside Diameter,
D2
Tolerance
Below +0.005
0 Minimum
Below 0
-0.005 Minimum
Size Mark ML MS
Cylinder Liner Inside
Diameter,
D1
+0.030 maximum
+0.020 minimum
L O X
below +0.020
+0.010 minimum
M O O
below +0.010
0 minimum
S X O
Cylinder Liner Inside Diameter, D1 Piston Outside Diameter, D2
105.900 mm (4.1692 in.) 105.794 mm (4.1651 in.)