Yamaha TTR90 Fahrer- Und Wartungshandbuch Seite 232

VALVES AND VALVE SPRINGS
2. Lap:
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
• Apply a coarse lapping compound to the
Do not let the compound enter the gap
between the valve stem and the guide.
• Apply molybdenum disulfide oil to the
• Install the valve into the cylinder head.
• Turn the valve until the valve face and
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
• Apply a fine lapping compound to the
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
• Apply Mechanic's blueing dye (Dykem) to
• Install the valve into the cylinder head.
• Press the valve through the valve guide
• Measure the valve seat width again. If the
4 - 19
• Valve face
• Valve seat
valve face.
CAUTION:
valve stem.
valve seat are evenly polished, then clean
off all of the compound.
valve face and repeat the above steps.
the valve face.
and onto the valve seat to make a clear
pattern.
valve seat width is out of specification,
reface and relap the valve seat.
ENG