Yamaha F4A - Valve Lapping

E
ROCKER ARM AND VALVES
POWR
3 The valve seat is too narrow and is near the
valve margin.
4 The valve seat is too narrow and is near the
bottom edge of the valve face.
5-20
Valve seat cutter set Desired result
First: To achieve a
Use
0° cutter centred valve
Second: seat with the
45° cutter proper with.
Valve seat cutter set Desired result
First: To centred the
Use
60° cutter valve seat and
Second: increase its
45° cutter width.
3
4
Valve lapping
NOTE:
After refacing the valve seat of replacing
the valve and valve guide, the valve seat
and valve face should be lapped.
Lapping steps:
8 Apply a coarse lapping compound to
the valve face.
cC
Be sure no compound enters the gap
between the valve stem and guide.
8 Apply a molybdenum disulfide oil to
the valve stem.
8 Install the valve in to the cylinder
head.
8 Turn the valve until the valve face
and valve seat are evenly polished,
then clean off all compound.
NOTE:
To obtain the best lapping results, light-
ly tap the valve seat while rotating the
valve back and forth between your
hands.