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seat have been re-surfaced and now require
final light grinding operation for perfect seal-
ing.
b. Apply a small amount of coarse lapping com-
pound t o valve face. Insert the valve into the
head. Rotate the va!ve until thevalveandvalve
seat are evenly polished. Clean of f the coarse
compound, then follow the same procedure
with fine compound,
Continue lapping until the valve face shows a
complete and smooth surface all the way
around. Clean of f the compound material.
Apply bluing dye to the valve face and rotate
the valve face for full seat contact which is
indicated by a shiny surface all around the
valve face where the bluing has been rubbed
away.
c. Valve leakage check
After all work has been performed on the
valve and valve seat, and all head parts have
been assembled, check for proper valve/valve
seat sealing by pouring solvent into each of
the intake ports, then the exhaust ports. There
should be no leakage past the seat. I f fluid
leaks, disassemble and continue t o lap with
fine lapping compound. Clean a ll parts thor-
oughly, reassemble and check again with
solvent. Repeat this procedure as often as
necessary t o obtain a satisfactory seal.
D. Valve Spring and Lifters
1. Checking the valve springs
a.
This engine uses two springs of different sizes
t o prevent valve float or surging. The chart
below shows the basic value characteristics.
b. Even though the spring is constructed of dur-
able spring steel, it gradually loses some of it's
is
tension. This
ening of free length. Use
Free length
Installed length (valve closed)
Installed pressure
Compressed length (valve open)
Compressed pressure
Allowable tilt from vertical
a
evidenced by
gradual short-
a
vernier caliper t o
39.9mm (1.571")
34.5mm (1.358")
16.27~18.73 kg (35.9~41.3 Ib)
26.0mm (1.024")
49.29~56.71 kg (108.7~125 Ib)
1.6mm (.063") or 2.5°
a
measure spring free length. I f the free length
of any spring has decreased more than 2mm
(.080")
c. Another symptom of a fatigued spring is in-
sufficient spring pressure when compressed.
This can be checked using a valve spring com-
pression rate gauge. Test each spring indivi-
dually. Place it in the gauge and compress the
spring first t o the specified compressed length
with the valve closed (all spring specifications
can be found in the previous section, Valve
Spring), then t o the length with the valve
open. Note the poundage indicated on the
scale a t each setting. Use this procedure with
the outer springs, then the inner springs.
NOTE: All valve springs must be installed with
greater pitch upward as shown.
OUTER
from i t s specification, replace
0
INNER
35.6mm (1.402")
31.5mm (1.240")
6.75~8.25 kg (14.9~18.2 Ib)
23.0mm (.908")
25.57~29.43 kg. (56.4~64.9 Ib)
it.
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