Suzuki DR 125, Service Manual

Page: 61 / 222

ENGINE 3-25
INITIAL SEAT CUT
• Using the 45° cutter, descale and clean up the seat. Rotate
the cutter one or two turns.
• Measure the valve seat width
W
after every cut.
• If the valve seat is pitted or burned, use the 45° cutter to con-
dition the seat some more.
NOTE:
Cut only the minimum amount necessary from the seat to pre-
vent the possibility of the valve stem becoming too close to the
rocker arm for correct valve contact angle.
TOP NARROWING CUT
• If the contact area is too high on the valve, or if it is too wide,
use the 15° cutter to lower and narrow the contact area.
(Use the 15° cutter.)
FINAL SEAT CUT
• If the contact area is too low or too narrow, use the 45° cutter
to raise and widen the contact area.
NOTE:
After cutting the 15° angle, it is possible that the valve seat (45°)
is too narrow. If so, re-cut the valve seat to the correct width.
• After the desired seat position and width is achieved, use the
45°cutter very lightly to clean up any burrs caused by the pre-
vious cutting operations.
45˚
Contact area too high and too wide on face of
valve
15˚
Contact area too low and too narrow on face
of valve