Yanmar 4LHA-HTP Operation Manual page 342

Chapter 2 Basic Engine
5. Piston and Piston Pins
5-1.3 Replacing the piston
A floating type piston pin is used in this engine. The piston pin
can be pressed into the piston pin hole at room temperature
(coat with oil to make it slide in easily).
5-2 Piston pin
Measure the outer diameter and replace the pin if it is exces-
sively wom.
Piston pin insertion hole dia.
Piston pin outside dia.
Standard clearance
5-3 Piston rings
There are 2 compression rings and 1 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.
5-3.1 Measuring the rings
Measure the thickness and width of the rings, and the ring-to-
groove clearance after installation. Replace if wear exceeds
the limit.
Width
Thickness
2-22
M4LHA Series
mm(in.)
All
37.000-37.011
(1.4567-1.4578)
36.994-37.000
(1.4565-1.4567)
0.017
(0-0.0007)