16
Check the valve guide bore. Insert the valve and
make sure that it moves smoothly through the
bore without any wobble. Figure 1 shows a good
valve guide. Figure 2 shows a valve guide with
abnormal wear that would allow the valve to
wobble. The valve head could eventually break
off and fall into the combustion chamber,
damaging the engine. This valve guide must be
reamed or replaced. Figure 3 shows a valve
guide with a bore that is not centered. This valve
guide must be replaced.
Valve Guides – Replace:
Place the new valve guides in the freezer
compartment of your refrigerator for one hour.
Use a valve guide driver to drive out the old
valve guides. Take care that you do not damage
the cylinder head while driving out the old valve
guides.
Install the new valve guides from the valve
spring side of the cylinder head. Use the valve
guide driver (2) to drive the exhaust valve guide
in until the clip is fully seated (1). Drive the
intake valve guide in until the top of the valve
guide extends 1mm above the cylinder head (3).
After installation check each valve guide for
damage. If damaged, repeat the removal and
installation process using a new valve guide.
Use a micrometer to measure the outside
diameter of the valve stem. Refer to the
following table.
If the diameter of the valve is at or below the
minimum, replace the valve.
Subtract the diameter of the valve stem from the
internal bore of the valve guide to determine the
valve stem-to-guide clearance. If the clearance
is more than the maximum shown in the
following chart, determine if a new guide or a
new valve is the best choice to bring the
clearance back into tolerance.
Valves:
Check the valves for damage. Check the valve
head (1), valve margin (2), and valve face (3) for
damaged or burnt areas. Check the valve neck
(4) for unusual wear. Check the valve stem (5)
for wear, scoring, or bends. If any damage is
found, replace the valve.
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