Yamaha TT-R90(S), Owner'S Service Manual

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ENG
CYLINDER AND PISTON
Piston ring
1. Measure:
●
Ring side clearance
Use a feeler gauge.
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 5 mm (0.20 in) into the cylinder.
Push the ring with the piston crown so that the
ring will be at a right angle to the cylinder bore.
a
5 mm (0.20 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.
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)
End gap
Standard Limit
Top ring
0.10 ~ 0.25 mm
(0.004 ~ 0.010 in)
0.4 mm
(0.016 in)
2nd ring
0.10 ~ 0.25 mm
(0.004 ~ 0.010 in)
0.4 mm
(0.016 in)
Oil ring
0.2 ~ 0.7 mm
(0.01 ~ 0.03 in)
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