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Page Title:
Section II. VALVES AND VALVE SPRINGS |
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 TM 5-4320-237-15
Section II. VALVES AND VALVE SPRINGS
(2) Inspect valves for burned, pitted, or
91. General
cracked faces; replace a burned,
a. The engine uses a conventional valve-in-
cracked, or deeply pitted valve.
block arrangement. Valves are held closed by
(3) Measure the valve stem clearance in
action of the valve springs unless the force of
guides; refer to table 1 for clear-
the springs is overcome by action of the cam-
ances. Replace a defective guide
shaft against the valves through the valve
tappets. The lobes of the camshaft raise the
(4) Inspect valve springs for cracks or
tappets which strike the valve and raise the
pitting. Replace cracked or pitted
valves from their seats to allow intake and ex-
springs.
haust at the required time. A valve-to-tappet
c. Regrinding Valves.
clearance must exist to assure that valves will
(1) Regrind valve, valve seat, and valve
seat fully when tappets are in the lowest po-
seat insert only when there is evi-
sition. This clearance must be 0.008 inch for
dence of warping or deep pits.
inlet valves and 0.014 inch for exhaust valves.
(2) Using a valve seat grinding tool,
The clearances are adjusted by grinding off
grind the seats to a 45 angle and
the ends of the valve stems.
then grind the valve faces at a 45
b. The exhaust valve is provided with a
angle with a valve refacer grinder.
valve rotator which imparts a slight rotation
(3) Valves must be lapped with a suit-
to the exhaust valve each time it operates. This
able lapping compound o r they
helps to prevent sticking valves, provides a
will leak within the first few hours
wiping action which cleans the exhaust valve
of operation because of improper
seat, and helps to provide even heat dissipa-
seating.
tion.
(4) Clean valve seat and faces with an ap-
proved cleaning solvent and dry
92. Valves and Valve Springs
thoroughly.
a. Removal and Disassembly.
(5) After lapping the valves, remove
(1) Remove the engine (para 73). Re-
them from the block and wash the
move the carburetor (para 52). Re-
valves and block with an approved
move the muffler ( para 62). Re-
cleaning solvent.
move the cylinder head (para 65).
(6) After grinding valves, check valve
Remove the tappet cover (para 66).
tappet clearance (para 66). If it is
(2) Refer to figure 4 0 and remove
not great enough, carefully grind
and disassemble the valves
and
off the ends of the valve stem to pro-
springs.
vide required clearance.
b. Cleaning, Inspection, and Repair.
d. Reassembly and Installation.
(1) Clean the valves with a wire brush
(1) Refer to figure 40 and install the
valves and associated parts
to remove all carbon deposits and
(2) Install the tappet cover (para 66). In-
gum deposits. Clean valves seats,
ports, and guides in cylinder block;
stall the cylinder head (para 65). In-
clean top of cylinder block. Wash
stall the muffler (para 62). Install
the carburetor (para 52). Install the
springs with an approved cleaning
solvent and dry thoroughly.
engine (para 73).
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