Piston And Ring Inspection - Honda CB450 1968 Service Manual

36 3. ENGINE
Fi g . 3. 64 Riston outer diameter measu ring
l!P!::"!'!'11"'111~T::I"' .,,,.,-,
f i g . 3 . 6 5 Piston outer diameter measuring
(D Piston
®
M icrocneter
fig. 3 . 66 Measuring the clearance bet ween piston and
piston ring
(D
Piston
@
Piston r ing
@
Thickness gouge
Fig . 3. 6 7 Piston ring end gap measuring
(D Thickness gauge
®
Piston ring
@
Cylinder
j
X. Piston and Piston Ring !inspection
l . Before inspectio n. carbon adhering to the
pisto n head or ring groove should be removed ,
using care not to scratch piston.
NOTE:
Emery paper should not be used for removing
the carbon , use a carbon scraper.
2. Piston diameter .
(Fig. 3. 64, 3. 65)
D = 69 .95-69.97 mm (2.754- 2.7 55 in}
d=D
0
-0 .2 4 I0.0095 in} -0.26 !0102 in}
NOTE:
Oversize pisto n ore ava ilable from D
=
70.22
mm (2. 7 65 in} to 70. 97 mm (2. 79 4 in} in four
difference sizes at an increment of 0. 25 mm
I0.01 inl.
3. Ring groove cle arances
When a new piston ring is fitted. (Fig. 3. 66)
Item
i
Standard value
I Serviceab le limit
'
0.040-0.070 mm
I
Replace if over
Top ring
0. 15mm
(0.0016-0.0028 inl
10.006 inl
2nd rin g
0.020- 0.0 45mm
I
Replace
~
l~ver
10.0008 -0 .0018 in! io:oo:i~J
O il ring
0 .0 l 0-0 .040 mm Replace
~
i°ver
I0. 0004- 0.0016 inll
IO:o;
4 minl
4. Piston pin diame ter.
Item
I Standard volue
I
Serviceable limi t
Piston
pin dia.
16.994- 17.00m m
I
R eplace i//;t:m
10.6690-0 .66 93 ,nJ
10
_
6673
inl
Piston
. .
17
_
002
_
17
_
00 8
mm l Replace if aver
pin bore
I
10.6693-0 .6696 inll
t6 .~)
3 ~~nl
5. Piston ring and gap.
Measure the ring gap by inserting the piston
ring into the cy linder so that the ring is at right
angle to the cy linder axis, the gap should be
measured with a thickness gauge. (Fig. 3. 67)
Item
I
Standard value
I
Serviceable limit
I
I
I
'
Tap.
0.3-0.5mm
I
Replace
if
over
Second ring
IO.O
12-0 .03 inl
0.8 mm 10.031 in!
Oi l ring
0.2-0.4mm
I
Replace if over
10.008-0 .016 in! 0.8 mm I0.031 inl