Yamaha TTR90 Fahrer- Und Wartungshandbuch Seite 244

CYLINDER AND PISTON
Piston pin
1. Inspect:
• Piston pin
Blue discoloration/grooves →
Replace, then inspect the lubrication sys-
tem.
2. Measure:
• Piston pin outside diameter
• Piston pin bore inside diameter
Measurement steps:
• Measure the piston pin outside diameter
a.
If out of specification, replace the piston
pin.
Outside diameter (piston pin):
12.996 ~ 13.000 mm
(0.5117 ~ 0.5118 in)
<Limit>:12.976 mm (0.5109 in)
• Measure the piston inside diameter b.
If out of specification, replace the piston.
Inside diameter (piston):
13.002 ~ 13.013 mm
(0.5119 ~ 0.5123 in)
<Limit>: 13.045 mm (0.5136 in)
ASSEMBLY AND INSTALLATION
Piston
1. Install:
• Piston rings
(onto the piston)
NOTE:
• Be sure to install the piston rings so that the
manufacturer's
located on the upper side of the rings.
• Lubricate the piston and piston rings liberally
with engine oil.
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ENG
marks or numbers are