Suzuki GN125F Service Manual page 44

Check the contact width.
09900-20103: Vernier calipers
Valve seat width:
If contact width is too small, cut the valve seat with a 45
reamer to raise.
If the valve seat contact width is too big, cut the valve seat
out side 1/8 with a 30 reamer and cut the bottom 1/8 with a
o
60 reamer to lower.
Check the contact width.
If the width is out out off the specication, repeat the operation
above steps.
After the desired seat position and width is achieved, apply a
layer of lapping compound and use the reamer very lightly to
service the valve seat. After servicing, clean up the remaining
lapping compound on the cylinder head and valve.
Check the valve seat contact surface again.
If the lapping pressure is too big, valve seat will be
possibly distorted or damaged. Change the lapping
tool angel frequently to prevent valve seat surface
from being uneven. If the lapping compound get into
the middle of the valve and valve guide will possibly
lead to damage.
0.9-1.1 mm
o
ENGINE
o
3-13
Width
o
45
o
30
o
60