TM 5-4310-227-15
Measure the valve face runout (f b e -
pansion pilot guide and drive the valve
low) .
seat firmly into the mounting recess.
(7) Inspect the valve seat inserts for evi-
(5) Grind the new valve seat insert light-
ly (e below).
dence of burning, pitting, or cracking.
Regrind slightly pitted or worn valve
Note. Always install the same type of
seat inserts (e below). Replace unserv-
valve seat insert that was removed.
iceable valve seat inserts (d below).
e. Grinding Valve Seat Inserts. Slightly
(8) Inspect the adjusting screws (19) for
rough, pitted, burned, or new valve seat in-
wear and for fit in the installed valve
serts should be reground. In most cases the in-
lifters (18). Be sure the adjusting
serts are worn or pitted very little and require
screws seat lightly in the valve lift-
only light refacing. Grind the valve seat angle
ers.
to a ture angle of 45. Remove only enough
(9) Replace all removed parts applicable
stock to clean up pits or grooves. If a new
to the valve system that have become
valve seat insert has been installed, as directed
worn, defective, or damaged. Refer to
in d above, it must be refaced. Always mark a
clean and even new seat when grinding valve
moval and installation instructions.
seat inserts.
c. Valve Guide Replacement. The valve stem
f. Refacing Valves. Measure the valve face
guides (3) are pressed into place and must be
runout with a dial indicator. If the runout is
removed if worn or defective.
excessive, grind the valve face at a 45 angle
(1) To remove a guide, first press the
on a precision valve grinder. Follow the in-
guide halfway into the valve chamber
structions for grinding furnished with the valve
with a rod or punch slightly smaller
grinder. Grind off only enough stock to remove
than the outside diameter of the valve
pits and grooves or to remedy excessive runout.
guide.
If the edge of the valve head is excessively thin
(2) Using a punch or rod and hammer,
after grindling or if runout persists, replace, the
carefully break off the lower half of
valve.
the valve guide in the valve chamber.
g. Valve Grinding. After refacing valves
Remove the broken lower half and
and valve seat inserts (e and f above) lightly
press the remaining upper half of the
tap the valves into the valve seat inserts with a
valve guide out of the valve guide
medium grade grinding compound as follows:
bore.
(1) Apply a light and even amount of
(3) Press the new valve guide into place.
grinding compound around the valve
Do not burr or damage the ends of
face and lightly lubricate the valve
the valve guide.
stem with oil.
d. Valve Seat Insert Replacement.
(2) Position the valve in its respective
(1) Using a valve seat insert removing
valve guide in the cylinder and crank-
tool, remove the valve seat insert (2)
case block.
from the cylinder and crankcase as-
(3) Using a valve grinding tool, press
sembly (4).
down lightly on the valve head and
(2) Clean all carbon and dirt from around
at the same time rotate the valve re-
the mounting recess for the valve seat
peatedly in both directions on the
insert.
valve seat insert. Then remove the
(3) Position an expansion pilot guide in
valve and observe the ring left by the
the valve stem guide (3).
grinding compound on the valve face
(4) Chill a new valve seat insert; then po-
and the valve seat insert. A valve
which is properly seated will have a
sition the insert on the cylinder and
r i n g completely around the valve
crankcase assembly (4). Set a valve
seat insert driving tool over the ex-
face.
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