Yamaha YZ 2023 Series, Owner'S Service Manual

Page: 82 / 378

ENGINE
3-6
EAM20135
ENGINE
EAM30226
ADJUSTING THE VALVE CLEARANCE
TIP
•
This section is intended for those who have ba-
sic knowledge and skill concerning the servic-
ing of Yamaha motorcycles (e.g., Yamaha
dealers, service engineers, etc.). Those who
have little knowledge and skill concerning ser-
vicing are requested not to undertake inspec-
tion, adjustment, disassembly, or reassembly
only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
• Make sure that the valve clearance is checked
or adjusted while the engine is cold (at room
temperature).
•
While the valve clearance is checked or adjust-
ed, make sure that the piston is positioned in
the top dead center (TDC).
1. Remove:
• Seat
•
Side cover (left/right)
• Air scoop (left/right)
Refer to “GENERAL CHASSIS” on page 4-1.
• Fuel tank
Refer to “FUEL TANK” on page 7-1.
• ECU (Engine Control Unit)
2. Remove:
• Spark plug
•
Cylinder head cover
Refer to “CAMSHAFT” on page 5-13.
3. Remove:
• Timing mark accessing screw “1”
•
Crankshaft end accessing screw “2”
• O-ring
4. Check:
•
Valve clearance
Out of specification

Regulate.
a. Turn the crankshaft counterclockwise with
a wrench.
b. Align the top dead center (TDC) mark “a”
on the generator rotor with the alignment
mark “b” on the crankcase cover.
TIP
Check that the alignment mark “c” on the cam-
shaft sprocket and the alignment mark “d” on the
intake camshaft sprocket are aligned with the
edge of the cylinder head.
c. Measure the valve clearance using a
thickness gauge “1”.
TIP
Record the measured reading if the clearance is
incorrect.
1
2
Valve clearance (cold)
Intake
0.12–0.19 mm (0.0047–0.0075 in)
Exhaust
0.17–0.24 mm (0.0067–0.0094 in)
Thickness gauge
90890-03268
Feeler gauge set
YU-26900-9
b
a
d
c