Inspecting The Pistons And Piston Pins - Yanmar 6LY3 series Service Manual

ENGINE
1. Check the rocker arm shaft and rocker arm
bearing.
• Measure the outer diameter of the rocker arm
shaft.
Figure 5-36
(1)
Figure 5-36
1 – Rocker Arm Hole Diameter
• Measure the inner diameter of the rocker arm
bearing.
• Replace if wear exceeds the stated limits.
Rocker Arm Specification
Inside Diameter of the
20.000-20.020 mm
Intake and Exhaust
Rocker Arm Bushing
Outside Diameter of the
19.970-19.990 mm
Intake and Exhaust
Rocker Arm Shaft
Clearance of the
Rocker Arm Shaft and
(0.0003-0.0019 in.)
Bushing at Assembly
• Replace the bearing if it moves in the rocker
arm.
• Replace the entire rocker arm if there is no
tightening clearance.
2. Check the rocker arm spring and replace it if it
is corroded or worn.
3. Check the rocker arm and valve top retainer
wear. Inspect the contact surface of the rocker
arm and replace it if there is abnormal wear or
flaking.
4. Inspect the contact surface of the adjusting bolt
and push rod. Replace it if there is abnormal
wear or flaking.
5-36
0005619
Standard Limit
20.090 mm
(0.787-0.788 in.) (0.790 in.)
19.955 mm
(0.786-0.787 in.) (0.785 in.)
0.010-0.050 mm 0.140 mm
(0.0055 in.)
© 2007 Yanmar Marine International
Inspecting the Cylinder Block and Components
Inspecting the Pistons and Piston
Pins
Pistons are made of a special light alloy with
superior thermal expansion characteristics. The top
of the piston forms a swirl-type combustion
chamber. The inside surface of the piston face is
cooled with oil-jet lubrication. NOTICE: Piston
shape differs among engine models. If an incorrect
piston is installed, engine performance will be
reduced. Check the applicable engine model
identification mark LY3 on the pistons for 6LY3
engines to ensure that the proper piston is being
used.
Figure 5-37
(6)
1 – Top Compression Ring
2 – Middle Compression Ring
3 – Oil Control Ring
4 – Piston Pin
5 – Circlip
6 – Engine ID Mark
6LY3 Service Manual
(1)
(2)
(3)
(4)
(5)
0005620
Figure 5-37