Yamaha WR450F Manuel D'atelier Du Proprietaire page 396

CYLINDER AND PISTON
Piston ring
1. Measure:
• Ring side clearance
Use a feeler gauge 1.
Out of specification → Replace the piston
and rings as a set.
NOTE:
Clean carbon from the piston ring grooves and
rings before measuring the side clearance.
Top ring
2nd ring
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)
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.
Top ring
2nd ring
Oil ring
4 - 48
ENG
Side clearance:
Standard
0.030 ~ 0.065 mm
(0.0012 ~ 0.0026 in)
0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)
End gap:
Standard
0.20 ~ 0.30 mm
(0.008 ~ 0.012 in)
0.35 ~ 0.50 mm
(0.014 ~ 0.020 in)
0.20 ~ 0.50 mm
(0.01 ~ 0.02 in)
<Limit>
0.12 mm
(0.005 in)
0.12 mm
(0.005 in)
<Limit>
0.55 mm
(0.022 in)
0.85 mm
(0.033 in)
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