Yamaha YZ450F(W), Owner'S Service Manual

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INSP
ADJ
IDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it up.
2. Adjust:
• Idle speed
VALVE CLEARANCE ADJUSTMENT
NOTE:
• The valve clearance should be adjusted
when the engine is cool to the touch.
• The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
• Seat
• Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
• Spark plug
• Engine upper bracket
• Hot starter plunger
Refer to “CARBURETOR” section in the
CHAPTER 4.
• Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
Adjustment steps:
• Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
• Turn the throttle stop screw
1
until the
specified engine idling speed.
NOTE:
Using a digital engine tachometer for idle
speed adjustment, detect the engine idling
speed by bringing the sensing element
c
of
the engine tachometer close to the ignition
coil
2
.
To increase idle speed
→
Turn the throttle stop screw
1
in
a
.
To decrease idle speed
→
Turn the throttle stop screw
1
out
b
.
Engine idling speed:
1,900 ~ 2,100 r/min
c
2