POWERHEAD
INSPECTION
25/30 Models
The difference between your measurements and
standard bore dimension
is
cylinder oversize.
Refer to
TECHNICAL DATA
on
p. 30 for dimen-
sions.
• The cylinder must not
be
oversize by more than
0.003 in. (0.08 mm).
IMPORTANT: If any cylinder
is
outside these tol-
erances, it must
be
bored oversize. One oversize
piston
is
available for this engine 0.030 in.
(0
.762
mm).
To
determine oversize bore, add 0.030
in
.
(0.762 mm) to the standard bore. Refer to TECH-
NICAL DATA
on
p.30.
It
is
permissible to have
one or more oversize pistons
in
an
engine.
Measure the piston diameter
in
at least two places
to
check piston condition. Make your measure-
ments 1/8 to 1/4
in.
(3.2 to 6.4 mm) above the bot-
tom edge of the piston skirt.
Piston
(side view)
C03082
Measure the diameter of the pistons as follows:
•
The
major
diameter of the piston
is
measured
90° from the wrist pin hole centerline.
•
The
minor
diameter of the piston is measured
in
line with the wrist pin hole centerline.
196
• The minor diameter must
be
smaller than the
major diameter by the
cam
dimension. See Pis-
ton Dimension Chart.
1
2----~
...
."
Piston
(top
view)
PCE0073A
1. Major diameter
2. Minor diameter
Piston Dimension Chart
Major Piston
Standard:
Oversize (.030):
2.9956
in
. 3.0256
in
.
Diameter
(76.11
mm)
(76.88 mm)
Cam
0.006 ± 0.001 in.
Dimension
(0
.
15
± 0.03 mm)
If the machining
on
the sides of the piston is worn
smooth
in
a pattern similar to the illustration,
replace the piston.
Piston (side view)
C03084
E
o
U
Qj
)(
~
Qj
~
~
I
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