Yamaha TT600R Service Manual page 227

INSPECTION AND REPAIR
Mill the valve seat as follows:
Section
A
B
C
Valve seat faults recorded by analysing the
valve seal surface:
[A] If the valve surface resembles that shown in
the figure, this means that the valve seat is
centred on the surface but is too wide.
Intervention
on the valve seat
30°
Cutter
type:
60°
[B] If the valve surface is like this, it means that
the valve seat is centred on the valve surface
but is too narrow.
Intervention
on the valve seat
Cutter
45°
type:
[C] If the valve surface is like this, it means that
the valve seat is too narrow and close to the
edge of the valve.
Intervention
on the valve seat
30° (before) Centring of seat and
Cutter
type:
45°
[D] If the valve surface is like this, it means that
the valve seat is too narrow and situated low
down near the lower edge of the valve sur-
face.
Intervention
on the valve seat
60° (first)
Cutter
type:
45°
5-25
ENG
Cutter
30°
45°
60°
Desired effect
Reduce valve seat
width to 1.0 mm
Desired effect
Centring of seat and
attainment of 1.0 mm
width
Desired effect
attainment of 1.0 mm
width
Desired effect
Centring of seat and
attainment of 1.0 mm
width