Yamaha 2001 YZ426F/LC Owner's Service Manual page 178

IDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
3 - 18
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Adjust:
Idle speed
Adjustment steps:
Adjust the pilot screw.
Refer to "PILOT SCREW ADJUSTMENT"
section.
Turn the throttle stop screw 1 until the
engine runs at the lowest possible speed.
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:
1,700 ~ 1,900 r/min
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:
Carburetor
Refer to "CARBURETOR" section in
the CHAPTER 4.
Spark plug cap
Engine stay (upper)
Cylinder head cover
Refer to "CAMSHAFTS" section in the
CHAPTER 4.
3. Remove:
Timing plug 1
Straight plug 2
O-ring
INSP
ADJ