TM 5-4930-227-14
(c) Finish the counterbore in the cylinder
block to provide the correct bore-to-insert inter-
ference. Chill the insert with dry ice and, using
a pilot driver, tab the insert into place with
light blows. Peen the insert to anchor in place.
(d) Reface the insert, if necessary, to make
its seat concentric with the valve stem bore. Check
concentricity with a dial indicator.
(e) Grind valve in seat to form a gas-
tight seat.
d. Regrinding Valves.
(1) Using a valve seat grinding tool, grind
the seats at a 45° angle and then grind the
valve faces at a 45° angle with a valve refacer
grinder.
(2) Valves must be lapped with a suitable
lapping compound or they will leak within the
first few hours of operation because of improper
seating.
(3) Clean valve seat and faces with an ap
proved cleaning solvent and dry thoroughly.
(4) After lapping the valves, remove them
from the block and wash the valves and block
with an approved cleaning solvent.
e. Reassembly. Refer to figure 6-4 and reas-
semble valves.
f. Installation.
(1) Install tappet cover plate (para 6-3).
(2) Install cylinder head (para 6-2).
(3) Install muffler (para 3-31),
(4) Install carburetor (para 3-28).
(5) Install engine (para 3-17).
6-5. Engine Base and Oil Pump
a. Removal.
(1) Remove the engine (para 3-17).
(2) Refer to figure 6-5 and remove the
engine base and oil pump.
b. Disassembly. Refer to figure 6-6 and disas-
semble the engine base and oil pump.
c. Cleaning, Inspection, and Repair.
(1) Clean all parts with an approved clean-
ing solvent and dry thoroughly.
(2) Inspect all parts for cracks, breaks, and
other damage.
(3) Inspect all hardware for damaged or
stipped threads.
(4) Replace a damaged or defective part.
d. Reassembly. Refer to figure 6-6 and reas-
semble the engine base and oil pump.
e. Installation.
(1) Refer to figure 6-5 and install the en-
gine base and oil pump.
(2) Install the engine (para 3-17).
Figure 6-4. Valves, removal, disassembly, reassembly
and installation.
1 Lock (4)
7 Rotator
2 Spring seat
8 Spring
3 Spring
9 Exhaust valve
4 Intake valve
10 cup (2)
5 Guide
11 Insert
6 Tappet (2)
12 Crankcase
6-3
