Yamaha BEARTRACKER YFM250XC, Service Manual

Page: 122 / 398

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ENG
INSPECTION AND REPAIR
ı
Valve seat is in the middle of the valve face
but too narrow.
Ç
Valve seat is too narrow and right up near
valve margin.
Î
Valve seat is too narrow and is located down
near the bottom edge of the valve face.
*********************************
Valve seat cutter set Desired result
Use 45˚ cutter
To achieve a uni-
form valve seat
width of 1.0 mm
(0.04 in)
Valve seat cutter set Desired result
Use
30˚ cutter To center the seat
and to achieve its
width of 1.0 mm
(0.04 in)
45˚ cutter
Valve seat cutter set Desired result
Use
60˚ cut-
ter, first
To center the seat
and increase its
width.
45˚ cutter
ı
Ç
Î
5.Lap:
●
Valve face
●
Valve seat
NOTE:
After refacing the valve seat or replacing
the valve and valve guide, the valve seat
and valve face should be lapped.
*********************************
Valve lapping steps:
●
Apply a coarse lapping compound 1 to
the valve face.
CAUTION:
Be sure no compound enters the gap
between the valve stem and guide.
4