Checking The Piston Pin; Checking The Timing Chain Guides; Installing The Piston And Cylinder - Yamaha SR400 2014 Service Manual

3. Measure:
• Piston ring end gap
Out of specification  Replace the piston
ring.
TIP
The oil ring expander spacer's end gap cannot
be measured. If the oil ring rail's gap is exces-
sive, replace all three piston rings.
Piston ring end gaps
Top ring
End gap (installed)
0.30–0.50 mm (0.0118–0.0197 in)
Limit
0.80 mm (0.0315 in)
2nd ring
End gap (installed)
0.30–0.50 mm (0.0118–0.0197 in)
Limit
0.80 mm (0.0315 in)
Oil ring
End gap (installed)
0.20–0.90 mm (0.0079–0.0354 in)
EAS24440

CHECKING THE PISTON PIN

1. Check:
• Piston pin
Blue discoloration/grooves  Replace the
piston pin and then check the lubrication sys-
tem.
2. Measure:
• Piston pin outside diameter "a"
Out of specification  Replace the piston pin.
Piston pin outside diameter
19.995–20.000 mm
(0.7872–0.7874 in)
Limit
19.975 mm (0.7864 in)
3. Measure:
• Piston pin bore inside diameter "b"
Out of specification  Replace the piston.
CYLINDER AND PISTON
Piston pin bore inside diameter
20.004–20.015 mm
(0.7876–0.7880 in)
Limit
20.045 mm (0.7892 in)
4. Calculate:
• Piston-pin-to-piston-pin-bore clearance
Out of specification  Replace the piston pin
and piston as a set.
• Piston-pin-to-piston-pin-bore clearance =
Piston pin bore inside diameter "b" -
Piston pin outside diameter "a"
Piston-pin-to-piston-pin-bore
clearance
0.004–0.020 mm (0.0002–0.0008
in)
Limit
0.070 mm (0.0028 in)
EAS23950

CHECKING THE TIMING CHAIN GUIDES

1. Check:
• Timing chain guide (intake side) "1"
• Timing chain guide (exhaust side) "2"
Damage/wear  Replace.
2
EAS24450

INSTALLING THE PISTON AND CYLINDER

1. Install:
• Oil ring expander "1"
• Lower oil ring rail "2"
• Upper oil ring rail "3"
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