Service manual
Table Of Contents
(3)
Replacing pistons
Replace the piston with a new one
if
the measure-
ment exceeds
the
service limit. Where any pistons
have
to
be replaced, the variance in weight among
the pistons
must
not
exceed the limit.
It
is
recommended
that
cylinder number be stamped
on
a piston selected
to
be used in a particular cy-
linder for convenience.
When the cylinder sleeves are bored
to
the
oversize,
pistons and piston rings
of
the same oversize
should be used. There are three oversizes for pistons
and piston rings, namely,
+0.25
mm
(0.00984
in.),
+0.50
mm
(0.01969 in.) and 0.75
mm
(0.0295 in.).
The variance in weight among the pistons per engine
should be
±5
grams (±0.18 oz), max.
(4) Piston
riD&
gaps
Check
the
ring gap
with
a thickness gauge
by
placing
the
ring
in
a new cylinder sleeve, and
pushing
the
pistOll true
and
square
in
the
bore.
Specifications
Item
Front
of
engine
t
Pilton
_ight
Piston weight marking
Piston
ring
Gap
Checking piston ring gap
Unit: mm (in.)
Standard
Service
limit
0.30
~0.50
1.5
Piston ring gap
(0.0118
~
0.0197)
(0.059)
(5) Piston ring
grooves
Insert the
compreuion
and oil rings
of
known
thicknesses
into
the
grooves, and measure the
side clearance
with
a straightedge and thickness
gauge@.
Measuring piston ring groove
Specifications
Unit·
mm
(in
)
Item
Standard
Repair
limit
Fit
in ring
No.1
compression
0.050
~ 0.085
0.20
ring
(0.00197
~
0.00335
(0.0079)
grooves
No.2
compression ring
0.025 ~ 0.060
0.15
Oil
ring
(0.00098
~
0.00236)
(0.0059)
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