Yamaha YBR125 Custom, Service Manual

Page: 95 / 218

ENG
Check and repair
4
.
Check:
Free movement of timing chain tensiener
.
Press the tensioning device lightly with finger,and screw
the tensioning device rod to dead with small screwdriver
When pressing screwdriver lightly with finger to loosen
the screwdriver, confirm that the tensioning device
come out smoothly.
Otherwise, replace the tensioning device assy.
Checking procedure:
Cylinder and piston
1.
2.
3.
4.
Clean:
Carbon deposit
(from top of piston and ring groove)
Check:
Side wall of piston
Wearing,scratch,damage
→ Replacement
Check:
Cylinder wall
Waring or scratch
→ Reboring cylinder or replacing
Measure:
Clearance between piston and cylinder
gauge
at
D3D4position
(
40 mm to cylinder top)
Measure cylinder diameter and “C ”with cylinder
Measuring procedure:
Note:
Measure cylinder diameter "C" from parallel and ver-
tical dire
ctio
n to cr
an
k
.
Then c
acul
ate the av
erag
e
va
lue
.
Sta
ndar
d valve of cyl
ind
er inner dia
met
er:
54.024 54.056 mm
Exceeding standard range → Replacement
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