Adjusting The Valve Clearance - Yamaha YZ450F Owner's Service Manual

1. Start the engine, and warm this up until the
oil has reached the specified temperature.
2. Attach the pocket tester with temperature
probe "1" to the oil drain bolt.
Oil temperature
55–65 °C (131–149 °F)
3. Install:
• Digital tachometer
Digital tachometer
90890-06760
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
a
4. Measure:
• Engine idling speed
Out of specification  Regulate.
Engine idling speed
1900–2100 r/min
5. Adjust:
• Engine idling speed
1
1
a
3-17
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a. Turn the starter knob/idle screw "1" in the di-
rection of "a" or "b" to make an adjustment.
b
a
Engine idling speed  De-
Direction "a"
creases.
Engine idling speed  In-
Direction "b"
creases.
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ADJUSTING THE VALVE CLEARANCE

EASB111087
TIP
• This section is intended for those who have
basic knowledge and skill concerning the ser-
vicing 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 ad-
justed, 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
2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFT" on page 5-12.
ENGINE
1