Yamaha YZF-R125, Service Manual

Page: 76 / 356

ENGINE
3-3
EAS20471
ENGINE
EAS20520
ADJUSTING THE VALVE CLEARANCE
The following procedure applies to all of the
valves.
NOTE:
• Valve clearance adjustment should be made
on a cold engine, at room temperature.
• When the valve clearance is to be measured or
adjusted, the piston must be at top dead center
(TDC) on the compression stroke.
1. Remove:
• Bottom cowling
Refer to “GENERAL CHASSIS” on page 4-1.
• Fuel tank
Refer to “FUEL TANK” on page 7-1.
2. Disconnect:
• Spark plug cap
3. Remove:
• Spark plug
• Ignition coil “1”
• Plastic locking tie “2”
4. Disconnect:
• Main switch coupler “3”
• Left handlebar switch couplers “4”
• Cylinder head cover
• Cylinder head cover gasket
Refer to “CYLINDER HEAD” on page 5-7.
NOTE:
When removing the cylinder head cover, lift it out
from between the frame tubes.
5. Remove:
• Timing mark accessing screw “1”
• Crankshaft end accessing screw “2”
6. Measure:
• Valve clearance
Out of specification
→
Adjust.
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a. Turn the crankshaft counterclockwise.
b. Align the TDC mark “a” on the generator rotor
with the stationary pointer “b” on the genera-
tor cover.
c. Check that the cam lobes are positioned as
shown in the illustration.
d. Measure the valve clearance with a thickness
gauge “1”.
Out of specification
→
Adjust.
1
2
3
4
4
Valve clearance (cold)
Intake
0.10–0.14 mm (0.0039–0.0055 in)
Exhaust
0.20–0.24 mm (0.0079–0.0094 in)
1
2
b
a
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