Yanmar 6LY3 series Service Manual page 103

Inspecting the Cylinder Block and Components
12/05
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.
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.
Cylinder Liner Inside
Diameter,
D1
Cylinder Liner Inside Diameter, D1
105.900 mm (4.1692 in.)
6LY3 Service Manual
Tolerance
+0.030 maximum
+0.020 minimum
below +0.020
+0.010 minimum
below +0.010
0 minimum
© 2007 Yanmar Marine International
Piston Outside Diameter
Piston
ID Standard
Mark
105.799-105.809 mm
L
(4.1653-4.1656 in.)
105.794-105.799 mm
ML
(4.1651-4.1653 in.)
105.789-105.794 mm
MS
(4.1649-4.1651 in.)
105.779-105.789 mm
S
(4.1645-4.1649 in.)
Figure 5-38
1 – Piston Skirt
Below +0.005
0 Minimum
Size Mark
L
M
S
Piston Outside Diameter, D2
105.794 mm (4.1651 in.)
ENGINE
Clearance
Between
Limit
Piston and
Cylinder
105.780
0.111-0.131 mm
mm
(0.0043-0.0051
(4.1645
in.)
(1)
0005621
Figure 5-38
Piston Outside Diameter,
D2
Below 0
-0.005 Minimum
ML MS
O X
O O
X O
in.)
5-37