TM 10-4930-204-13
(3) Inspect valve springs for cracks or pitting. Replace
cracked or pitted springs.
(4) Inspect valve seat insert for looseness and pitting.
Replace defective valve seat insert in the following manner:
(a) Use a puller to remove insert from exhaust valve
opening.
(b) Clean all carbon out of insert counterbore in
cylinder block and clean valve stem guide bore.
(c) Finish counterbore in cylindler block to provide
correct bore-to-insert interference.
Chill insert with dry ice and,
using a pilot driver, tap insert into place with light blows. Peen
insert to anchor in place.
(d) Reface insert, if necessary, to make its seat
concentric with valve stem bore.
Check concentricity with a dial
indicator.
(e) Grind valve in seat to form a gastight seal.
c.
Regrinding Valves.
(1) Regrind valve, valve seat, and valve seat insert only
when there is evidence of warping or deep pits.
(2) Using a valve seat grinding tool, grind seats at a 45
degree angle and then grind the valve faces at a 45 degree angle with
a valve refacer grinder.
(3) Valves must be lapped with a suitable lapping compound
or they will leak within the first few hours of operation because of
improper seating.
(4) Clean valve seat and faces with drycleaning solvent
(item 1, App. F), and dry thoroughly.
(5) After lapping valves, remove them from the block and
wash valves and block with drycleaning solvent (item 1., App. F).
d.
Reassembly and Installation.
(1) Install inserts (11, fig. 5-2) and cups (10).
(2) Install tappets (6), guides (5); insert exhaust valve
(9), and intake valve (4).
(3) Install springs (8 and 3), spring seats (7 and 2).
(4) Install cylinder head, tapped inspection plate,
muffler, and carburetor (para 4-24).
5-7
