2008 YAMAHA YZ450F Owners Manual

Page 81 of 188

YAMAHA YZ450F 2008  Owners Manual 4-13
CARBURETOR
ADJUSTING THE ACCELERATOR 
PUMP TIMING
Adjustment steps:
In order for the throttle valve height 
"a" to achieve the specified value, 
tuck under the throttle valve plate "1" 
the rod "

Page 82 of 188

YAMAHA YZ450F 2008  Owners Manual 4-14
CAMSHAFTS
CAMSHAFTS
REMOVING THE CYLINDER HEAD COVER
Order Part name Qty Remarks
Seat and fuel tank Refer to "SEAT, FUEL TANK AND SIDE 
COVERS" section.
Hot starter plunger Refer to "CARBURETOR"

Page 83 of 188

YAMAHA YZ450F 2008  Owners Manual 4-15
CAMSHAFTS
REMOVING THE CAMSHAFTS
Order Part name Qty Remarks
1 Timing mark accessing screw1 Refer to removal section.
2 Crankshaft end accessing screw 1 Refer to removal section.
3 Timing chain

Page 84 of 188

YAMAHA YZ450F 2008  Owners Manual 4-16
CAMSHAFTS
REMOVING THE CAMSHAFT
1. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw 
"2"
2. Align:
• T.D.C. mark
With align mark.
Checking steps:
a. Turn the crank

Page 85 of 188

YAMAHA YZ450F 2008  Owners Manual 4-17
CAMSHAFTS
Measurement steps:
a. Install the camshaft onto the cylin-
der head.
b. Position a strip of Plastigauge
® 
"1" onto the camshaft.
c. Install the clip, dowel pins and 
camshaft caps.

Page 86 of 188

YAMAHA YZ450F 2008  Owners Manual 4-18
CAMSHAFTS
Do not turn the crankshaft during 
the camshaft installation. Damage 
or improper valve timing will re-
sult.
d. Install the clips, camshaft caps "4" 
and bolts (camshaft cap) "5".
•

Page 87 of 188

YAMAHA YZ450F 2008  Owners Manual 4-19
CYLINDER HEAD
CYLINDER HEAD
REMOVING THE CYLINDER HEAD
Tighten the cylinder head bolts to 30 Nm (3.0 m•kg, 22 ft•lb) in the proper tightening sequence, remove and retighten the 
cylinder head

Page 88 of 188

YAMAHA YZ450F 2008  Owners Manual 4-20
CYLINDER HEAD
CHECKING THE CYLINDER HEAD
1. Eliminate:
• Carbon deposits (from the com-
bustion chambers)
Use a rounded scraper.
Do not use a sharp instrument to 
avoid damaging or scratching: