Valve Spring - Yamaha YFM250XL(C) Service Manual

INSPECTION AND REPAIR
Apply a molybdenum disulfide oil to the
valve stem.
Install the valve into the cylinder head.
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all compound.
NOTE:
To obtain the best lapping result, lightly tap
the valve seat while rotating the valve back
and forth between your hand.
Apply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
Be sure to clean off all compound from the
valve face and valve seat after every lap-
ping operation.
Apply the Mechanic's bluing dye 2
(Dykem) to the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Remove the valve from the cylinder head.
Measure the valve seat width a again. If
the valve seat width is out of specification,
reface and lap the valve seat.
*********************************

VALVE SPRING

1.Measure:
Valve spring free length a (inner and
outer)
Out of specification → Replace.
Valve spring free length
Inner spring (IN/EX) Outer spring (IN/EX)
35.5 mm (1.4 in)
4 - 25
ENG
37.2 mm (1.46 in)
4