lug pattern YAMAHA YZ426F 2001 Notices Demploi (in French)

4 - 21
ENG

CAMSHAFTS
REMOVAL POINTS
Camshaft
1. Remove:
l
Timing plug
1

l
Straight plug
2

2. Align:
l
“I” mark
With stationary pointer.
Checking steps:
l
Turn the crankshaft counterclockwise with
a wrench.
l
Align the “I” mark
a
on the rotor with the
stationary pointer
b
on the crankcase
cover. When the “I” mark is aligned with
the stationary pointer, the piston is at the
Top Dead Center (T.D.C.).
NOTE:

l
In order to be sure that the piston is at Top
Dead Center, the punch mark
c
on the
exhaust camshaft and the punch mark
d
on the intake camshaft must align with the
cylinder head surface, as shown in the
illustration.
l
If there is no clearance, rotate the crank-
shaft counterclockwise one turn.
3. Loosen:
l
Tensioner cap bolt
1

4. Remove:
l
Timing chain tensioner
2

5. Remove:
l
Bolt (camshaft cap)
1

l
Camshaft caps
2

NOTE:

Remove the bolts (camshaft cap) in a criss-
cross pattern, working from the outside in.
CAUTION:

The bolts (camshaft cap) must be removed
evenly to prevent damage to the cylinder
head, camshafts or camshaft caps.

4 - 28
ENGCYLINDER HEAD
INSPECTION
Cylinder head
1. Eliminate:
lCarbon deposits (from the combustion
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid dam-
aging or scratching:
lSpark plug threads
lValve seats
2. Inspect:
lCylinder head
Scratches/damage ® Replace.
3. Measure:
lCylinder head warpage
Out of specification ® Resurface.
Cylinder head warpage:
Less than 0.05 mm (0.002 in)
Warpage measurement and resurface-
ment steps:
lPlace a straightedge and a feeler gauge
across the cylinder head.
lUse a feeler gauge to measure the
warpage.
lIf the warpage is out of specification,
resurface the cylinder head.
lPlace a 400 ~ 600 grit wet sandpaper on
the surface plate, and resurface the head
using a figure-eight sanding pattern.
NOTE:
To ensure an even surface rotate the cylin-
der head several times.