Piston Rings - Yanmar YM155d Service Manual

NOTES:
( I ) Measure rhe outer diameter of the piston at the piston skirt section, at right angles
to the lrris of the piston pin
(2) Mensure the clearance between the piston and the cylinder liner by comparing the
outer diameter
of
the piston and the inner diameter of the cylinder liner. The clearance
is the difference between the minimum clearance figure obtained and the outerdimneter
of the piston.
(3) Replacing Pistons
(3.1) Disassembly
3 .
PISTON RINGS
Replacement limit
0.0078 (0.2)
0.0079 10.2)
0.0079 (0.2)
0.0059 (0.151
Standard dimension
0.0019-0.0033
(0.050-0.0851
0.0008-0.0022
(0.020-0.0551
0.0008-0.0022
(0.020-0.0551
0.0008-0.0022
(0.020-0.0551
r
Item
a)
Detach the two piston pin retaining rings;
The piston rings have Teflon@ coatings in order
b)
Heat up the piston t o 176"
-
212°F (80"
t o achieve good break-in properties.
-
100°C):
Testing equipment
Thickness gauge(
3.
The piston rings are as follows:
C)
Remove the piston pin by tapping
it
with
a lead bar and a hammer.
No.1 ring Barrel face type:
Provides and maintains good seal-
(3.2) Assembly
ing properties and carbon crush-
ing properties; also prevents car-
e
a)
Fit in one of the piston pin retaining rings;
bon sticking. Is chrome plated to
achieve good wear-resisting pro-
Piston ring grooves
clearance:-
No. 1
No. 2
No. 3
No. 4
perties.
.b)
Heat up the piston t o 176"
-
212°F (80"
-
100°C); No.2 & 3 Taper face type:
Provides and maintains good seal-
C) Fit the piston pin in position;
ing properties and oil scraping
effects.
d)
Fit in the remaining piston pin retaining
ring. No.4 Bevel cutter type:
An oil ring, in which the empha-
After assembly check t o make sure that the piston
sis is upon oil scraping effects, is
and connecting rod move freely.
used.