Adjusting The Valve Clearance - Yamaha YZ450FX 2019 Owner's Service Manual

Digital tachometer
90890-06760
Digital tachometer
YU-39951-B
TIP
Get the high tension cord "1" of the ignition coil
pinched in the detector "a" of the digital tachom-
eter.
1 1
a a
4. Measure:
• Engine idling speed
Out of specification  Regulate.
Engine idling speed
1900–2100 r/min
5. Adjust:
• Engine idling speed
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the idle screw "1" in the direction of "a"
or "b" to make an adjustment.
b b
a a
Engine idling speed 
Direction "a"
Increases.
Engine idling speed 
Direction "b"
Decreases.
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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:
1
• Seat
• Side cover (left/right)
• Air scoop (left/right)
a
• Fuel tank
• ECU
2. Remove:
• Spark plug
• Cylinder head cover
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
1 1
4. Check:
• Valve clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the crankshaft counterclockwise with a
3-16
Refer to "GENERAL CHASSIS" on page 4-1.
Refer to "FUEL TANK" on page 7-1.
Refer to "CAMSHAFT" on page 5-11.
Out of specification  Regulate.
Valve clearance (cold)
Intake
0.10–0.17 mm (0.0039–0.0067 in)
Exhaust
0.15–0.22 mm (0.0059–0.0087 in)
wrench.
ENGINE
1
2