Yanmar 4LHA-HTP Operation Manual page 343

Chapter 2 Basic Engine
5. Piston and Piston Pins
Groove width
First First First
Ring width
piston piston piston
ring ring ring
Groove and
ring clearance
Groove width
Second Second Second
Ring width
piston piston piston
ring ring ring
Groove and
ring clearance
Groove width
Oil Oil Oil
Ring width
ring ring ring
Groove and
ring clearance
5-3.2 Measuring piston ring gap
Press the piston ring onto a cylinder and measure the
piston ring gap with a gauge.
Press on the ring about 30 mm (1.1811 in.) from the
bottom of the cylinder.
about 30mm
(1.181 lin.)
mm (in.)
Standard Wear limit
2.095 - 2 . 1 1 0
-
(0.0825 - 0.0831)
1 . 9 7 5 - 1.990
(0.0778 - 0.0783)
0.15
0 . 1 0 5 - 0 . 1 3 5
(0.0059)
(0.0041 -0.0053)
2.045 - 2.060
-
(0.0805-0.0811)
1 . 9 7 5 - 1.990
-
(0.0778 - 0.0783)
0.15
0.055 - 0.085
(0.0059)
(0.0022 - 0.0035)
3.020 - 3.035
-
(0.1189-0.1195)
2.92 - 2.99
-
(0.1169-0.1177)
0.15
0.030 - 0.065
(0.0059)
(0.0012-0.0026)
Gap
First piston ring gap
Second piston ring gap
Oil ring gap
5-3.3 Replacing the piston rings
(1) Thoroughly clean the ring grooves when replacing
piston rings.
(2) The side with the manufacturer's mark (near piston ring
gap) should face up.
(3) After fitting the piston ring, make sure it moves easily
and smoothly.
(4) Stagger the piston rings at 120° intervals, making sure
none of them line up with the piston.
2 n d
compression ring
2-23
, 4LHA Sen
mm (in.)
Wear limit
Standard
1.5
0.25 - 0.40
(0.0098 - 0.0157) (0.0591)
1.5
0.25 - 0.40
(0.0591)
(0.0098 - 0.0157)
1.5
0.3 - 0.5
(0.0118-0.0197) (0.0591)
T h e side with the maker's
mark faces up
1st compression ring
2nd compression ring
Oil ring
1st compression ring
Oil ring