Adjusting Valve Clearance; Specifications - Yamaha YZ450F Owner's Service Manual

Engine idling speed:
1,900–2,100 r/min
ADJUSTING THE VALVE
CLEARANCE
• This section is intended for those
who have basic knowledge and skill
concerning the servicing of Yama-
ha motorcycles (e.g., Yamaha deal-
ers, service engineers, etc.) Those
who have little knowledge and skill
concerning servicing are requested
not to undertake inspection, adjust-
ment, disassembly, or reassembly
only by reference to this manual. It
may lead to servicing trouble and
mechanical damage.
• The valve clearance should be ad-
justed when the engine is cool to
the touch.
1. Remove:
• Seat
Refer to "SEAT AND SIDE COV-
ERS" section in the CHAPTER 4.
• Fuel tank
Refer to "FUEL TANK" section in
the CHAPTER 6.
2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFTS" section
in the CHAPTER 4.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw
"2"
• O-ring
4. Check:
• Valve clearance
Out of specification → Adjust.
Valve clearance (cold):
Intake valve:
0.10–0.15 mm
(0.0039–0.0059 in)
Exhaust valve:
0.20–0.25 mm
(0.0079–0.0098 in)
Checking steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
b. Align the alignment mark "a" on
the rotor with the alignment mark
"b" on the crankcase cover.
Make sure that the alignment mark
"c" on the exhaust camshaft sprocket
and the alignment mark "d" on the in-
take camshaft sprocket are aligned
with the edge of the cylinder head.
c. Measure the valve clearance "e"
using a feeler gauge "1".
Record the measured reading if the
clearance is incorrect.
3-11
ENGINE
5. Adjust:
• Valve clearance
Adjustment steps:
a. Remove the camshaft (intake and
exhaust).
Refer to "CAMSHAFTS" section
in the CHAPTER 4.
b. Remove the valve lifter "1" and
the valve pad "2" with a valve lap-
per "3".
• Place a rag in the timing chain
space to prevent pads from falling
into the crankcase.
• Identity each valve lifter and pad
position very carefully so that they
can be reinstalled in their original
place.
c. Select the proper pad using the
pad selecting table.
Pad Availabili-
Pad range ty: 25 incre-
ments
No. 1.20 Pads are avail-
120–N mm–2. able in 0.05 mm
o. 240 40 mm increments
The thickness "a" of each pad is indi-
cated in hundredths of millimeters on
the pad upper surface.