Yamaha TDM850 1996 Service Manual page 144

VALVE AND VALVE SPRING
NOTE:
To obtain the best lapping result, lightly tap the
valve seat while rotating the valve back and forth
between your hand.
S 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 lapping operation.
S Apply the Mechanic's blueing dye (Dykem) b to
the valve face.
S Install the valve into the cylinder head.
S Press the valve through the valve guide and onto
the valve seat to make a clear pattern.
S Measure the valve seat width c again. If the
valve seat width is out of specification, reface
and lap the valve seat.
11. Measure:
S Free length (valve spring) a
Out of specification ! Replace.
12. Measure:
S Compressed force (valve spring) a
Out of specification ! Replace.
b Installed length
4-20
ENG
Free length (valve spring):
37.29 mm
<Limit>
35.20 mm
Compressed force:
10.0 X 11.6 kg at 30.39 mm