Yamaha WR250FM Bicycle User 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
ASSEMBLY AND INSTALLATION
Piston ring and piston
1. Install:
Piston ring
Onto the piston.
N
OTE:
Be sure to install the piston rings so that the
manufacturers marks or numbers are
located on the upper side of the rings.
Lubricate the piston and piston rings liberally
with engine oil.
Measurement steps:
Measure the outside diameter (piston pin)
a.
If out of specification, replace the piston
pin.
Outside diameter (piston pin):
15.991 ~ 16.000 mm
(0.6296 ~ 0.6299 in)
Measure the inside diameter (piston) b.
Inside diameter (piston):
16.002 ~ 16.013 mm
(0.6300 ~ 0.6304 in)
Calculate the piston pin-to-piston clear-
ance with the following formula.
Piston pin-to-piston clearance =
Inside diameter (piston)
b
Outside diameter (piston pin)
a
If out of specification, replace the piston.
Piston pin-to-piston clearance:
0.002 ~ 0.022 mm
(0.0001 ~ 0.0009 in)
<Limit>: 0.07 mm (0.003 in)