Yamaha YZF-R125 Service Manual: Checking the piston pin
1. Check:
- Piston pin
Blue discoloration/grooves
Replace the piston pin and then check the lubrication system.
2. Measure:
- Piston pin outside diameter "a"
Out of specification
Replace
the piston pin.
3. Measure:
- Piston pin bore diameter "b"
Out of specification
Replace
the piston.
4. Calculate:
Piston-pin-to-piston-pin-bore clearance
Out of specification 
Replace the
piston pin
and piston as a set.
- Piston-pin-to-piston-pin-bore clearance =
Piston pin bore diameter "b" -
Piston pin outside diameter "a"
Checking the piston rings
1. Measure:
Piston ring side clearance
Out of specification Replace the
piston
and piston rings as a set.
NOTE:
Before measuring the piston ring side clearance,
eliminate any carbon deposits ...
Installing the piston and cylinder
1. Install:
Top ring "1"
2nd ring "2"
Oil ring expander "3"
Lower oil ring rail "4"
Upper oil ring rail "5"
NOTE:
Be sure to install the piston rings so that the
manufacturer marks or ...
Other materials:
Installing the water pump
1. Install:
Water pump assembly "1"
O-rings "2"
NOTE:
Align the projection "a" on the impeller shaft
with the slit "b" on the camshaft sprocket bolt.
Lubricate the O-rings with a thin coat of lithiumsoap-
based grease.
2. Fill:
Cooling system
(with the specified amou ...
Checking and lubricating the brake and clutch levers
Brake lever
Brake lever
Clutch lever
Clutch lever
The operation of the brake and clutch
levers should be checked before each
ride, and the lever pivots should be lubricated
if necessary.
Recommended lubricants:Brake lever:
Silicone grease
Clutch lever:
Lithium-soap ...
Installing the rear wheel (disc)
1. Install:
Rear brake disc
NOTE:
Tighten the brake disc bolts in stages and in a
crisscross pattern.
2. Check:
Rear brake disc
Refer to "CHECKING THE REAR BRAKE
DISC" on page 4-33.
3. Lubricate:
Rear wheel axle
Contact surface of rear wheel hub and rear
wheel
Whee ...