Yamaha YZ450F(S), Owner'S Service Manual

Page: 328 / 642

4 - 45
ENG
CYLINDER AND PISTON
Piston ring
1. Measure:
●
Ring side clearance
Use a feeler gauge
1 .
Out of specification
→
Replace the pis-
ton and rings as a set.
NOTE:
Clean carbon from the piston ring grooves and
rings before measuring the side clearance.
2. Position:
●
Piston ring
(in cylinder)
NOTE:
Insert a ring into the cylinder and push it
approximately 10 mm (0.39 in) into the cylin-
der. Push the ring with the piston crown so that
the ring will be at a right angle to the cylinder
bore.
a
10 mm (0.39 in)
Side clearance:
Standard <Limit>
Top ring
0.030 ~ 0.065 mm
(0.0012 ~ 0.0026 in)
0.12 mm
(0.005 in)
2nd ring
0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)
0.12 mm
(0.005 in)
3. Measure:
●
Ring end gap
Out of specification
→
Replace.
NOTE:
You cannot measure the end gap on the
expander spacer of the oil control ring. If the oil
control ring rails show excessive gap, replace
all three rings.
End gap:
Standard <Limit>
Top ring
0.20 ~ 0.30 mm
(0.008 ~ 0.012 in)
0.55 mm
(0.022 in)
2nd ring
0.35 ~ 0.50 mm
(0.014 ~ 0.020 in)
0.85 mm
(0.033 in)
Oil ring
0.20 ~ 0.50 mm
(0.01 ~ 0.02 in)
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