valve. Lap the valve to the seat by rotating the
lapping stick back and forth by hand. Every 5 to
10 seconds, turn the valve 120" in the seat;
continue lapping until the contact surfaces of
the valve and the seat are a uniform grey. Do
not remove too much material.
4. Thoroughly clean the valves and cylinder
head in solvent to remove all grinding
compound. Any compound left on the valves
or the cylinder head will end up in the engine
and will cause serious damage.
5. After the lapping is finished and the valves
have been reinstalled in the head, the valve seal
should be tested. Check the seal of each valve
by pouring solvent into the intake and exhaust
ports. There should be no leakage past the
valve seat. If fluid leaks past any of the seats,
disassemble that valve assembly and repeat the
lapping procedure until there is no leakage.
Valve Stem Height
If the valve faces or seats were reground or
recut, the valves will drop deeper into the
cylinder head than before. Check valve stem
installed height before you assemble the valves
in the cylinder head. If the installed height is
incorrect, you may not be able to obtain proper
valve clearance with the available shims.
1. Insert the valve into the cylinder head and
measure valve stem height (Figure 48).
2. If the stem height is more than specified in
Table I, the valve seat has worn or been ground
too deep and the valve is too long for that
cylinder. Install new valves.
Do not grlnd the valve stem end to
correct the rnstalled helght. Grrndrng the
valve stern end can cause the valve llfter
to hlt the sprlng retalner and drop fhe
valve lnto the engrne whlle runnrng.
Valve Spring Inspection
As the valve springs wear, they become
weaker. The valve springs must be checked for
(Figure 49); have
your dealer perform this inspection. Replace
any spring that is weaker than the limit in Table
I at the end of this chapter.
Measure each valve spring (inner and outer)
for straightness by standing it on a flat surface
and butting it against the vertical edge of a
square (Figure 50). Install a new spring if the
gap at the top is more than the limit in Table 1.
Check the valve spring retainer and valve
keepers. If they are in good condition, they can
1. See Figure
39. Install the spring seats and
new oil seals on the valve guides.
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