Yamaha FT50C Service Manual page 116

POWR
b Previous contact width
5. Use a 45° cutter to adjust the contact
width of the valve seat to specification.
b Previous contact width
c Specified contact width
6. If the valve seat contact area is too wide
and situated in the center of the valve
face, use a 30° cutter to cut the top edge
of the valve seat, a 60° cutter to cut the
bottom edge to center the area and set
its width.
b Previous contact width
7. If the valve seat contact area is too nar-
row and situated near the top edge of the
valve face, use a 30° cutter to cut the top
edge of the valve seat. If necessary, use
a 45° cutter to center the area and set its
width.
5-29
Power unit
60°
S62Y5461
45°
S62Y5462
b Previous contact width
8. If the valve seat contact area is too nar-
row and situated near the bottom edge of
the valve face, use a 60° cutter to cut the
bottom edge of the valve seat. If neces-
sary, use a 45° cutter to center the area
and set its width.
b Previous contact width
9. Apply a thin, even layer of lapping com-
pound onto the valve seat, and then lap
the valve using a valve lapper (commer-
cially obtainable).
CAUTION:
Do not get the lapping compound on the
valve stem and valve guide.
62Y5A11