Valve Lapping - Yamaha F4 Service Manual

POWR
3
4
ROCKER ARM AND VALVES
3 The valve seat is too narrow and is near the
valve margin.
Valve seat cutter set
First:
0° cutter
Use
Second:
45° cutter
4 The valve seat is too narrow and is near the
bottom edge of the valve face.
Valve seat cutter set
First:
60° cutter
Use
Second:
45° cutter

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.
5-20
E
Desired result
To achieve a
centred valve
seat with the
proper with.
Desired result
To centred the
valve seat and
increase its
width.