remove seats YAMAHA TTR125 2001 Owners Manual

4 - 15
ENG

CYLINDER HEAD
4. Remove:
l
Bolt (camshaft sprocket)
1

l
Camshaft sprocket
2

NOTE:

Attach a wire
a
to the timing chain to prevent
it from falling into the crankcase.
5. Remove:
l
Bolts (cylinder head)
l
Cylinder head
NOTE:

l
Loosen the bolts 1/4 turn each and remove
then after all are loosened.
l
Loosen the bolts starting with the lowest
number one.
INSPECTION
Cylinder head
1. Eliminate:
l
Carbon deposits (from the combustion
chambers)
Use a rounded scraper.
NOTE:

Do not use a sharp instrument to avoid dam-
aging or scratching:
l
Spark plug threads
l
Valve seats
2. Inspect:
l
Cylinder head
Scratches/damage
®
Replace.
3. Inspect:
l
Cylinder head warpage
Out of specification
®
Re-surface.
Warpage measurement and re-surfacing
steps:
l
Attach a straightedge and a thickness
gauge on the cylinder head.
l
Measure the warpage.

4 - 27
ENGVALVES AND VALVE SPRINGS
3. Inspect:
lValve face
Pitting/wear ® Grind the face.
lValve stem end
Mushroom shape or diameter larger
than the body of the stem ® Replace.
4. Measure:
lMargin thickness a
Out of specification ® Replace.
5. Measure:
lRunout (valve stem)
Out of specification ® Replace.
NOTE:
lWhen installing a new valve always replace
the guide.
lIf the valve is removed or replaced always
replace the oil seal.
Margin thickness:
Intake:
0.4 ~ 0.8 mm
(0.0157 ~ 0.0315 in)
Exhaust:
0.8 ~ 1.2 mm
(0.0315 ~ 0.0472 in)
Runout limit:
0.01 mm (0.0004 in)
6. Eliminate:
lCarbon deposits
(from the valve face and valve seat)
7. Inspect:
lValve seats
Pitting/wear ® Reface the valve seat.