remove seats YAMAHA TTR125 2002 Owners Manual

4 - 15
ENGCYLINDER HEAD
4. Remove:
lBolt (camshaft sprocket) 1
lCamshaft sprocket 2
NOTE:
Attach a wire a to the timing chain to prevent
it from falling into the crankcase.
5. Remove:
lBolts (cylinder head)
lCylinder head
NOTE:
lLoosen the bolts 1/4 turn each and remove
then after all are loosened.
lLoosen the bolts starting with the lowest
number one.
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. Inspect:
lCylinder head warpage
Out of specification ® Re-surface.
Warpage measurement and re-surfacing
steps:
lAttach a straightedge and a thickness
gauge on the cylinder head.
lMeasure 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.