Yamaha TTR90(M), Owner'S Service Manual

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ENG
CYLINDER AND PISTON
Piston pin
1. Inspect:
●
Piston pin
Blue discoloration/grooves
→
Replace, then inspect the lubrication
system.
2. Measure:
●
Piston pin-to-piston clearance
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)
●
Measure the piston inside diameter
b
.
●
Calculate the piston pin-to-piston clear-
ance with the following formula.
Piston pin-to-piston clearance =
Bore size (piston pin)
b
–
Outside diameter (piston pin)
a
●
If out of specification, replace the piston.
Piston pin-to-piston clearance:
0.002 ~ 0.017 mm
(0.00008 ~ 0.00067 in)
<Limit>: 0.07 mm (0.003 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 marks or numbers are
located on the upper side of the rings.
●
Lubricate the piston and piston rings liberally
with engine oil.