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TM 5-4210-220-12
4-15. AUXILIARY POWER UNIT - Continued
(13)
Compress each valve spring (22) in turn to
remove valve half cones (19), spring seats (20,
23) springs (22), oil seal (21) (intake only) and
valve (24).
INSPECTION
(1)
Remove all scale from cylinder head and valves
using a wire brush and scraper.
(2)
Inspect each rocker arm, if badly warn, scored
or damaged, replace.
(3)
Inspect rocker arm pivot, diameter must be
(0.370 - 0.378 in.) (9.4 - 9.6 mm). Clearance
between pivot and rocker arms(s) bore should
be less than 0.004 in. (0.1 mm).
(4)
Replace rocker arm(s) or pivot as required.
(5)
Check rocker arm lube holes are clear. Clean
out with stiff wire as required.
(6)
Inspect push rods and protecting tube. Push
rods should be straight with end tips smooth.
The protecting tube must be undamaged.
(7)
Discard upper and lower push rod cover seals.
(8)
Inspect valves it valve heads are distorted, cracked, mushroomed or seat surface are worn excessively
replace, (see table). If valves are only slightly worn regrind seat surface to 45 deg. on valve grinder.
B
A-B
C
D
E
in.
In.
In.
In.
In.
(mm)
(mm)
(mm)
(mm)
(mm)
0.275-0.276
0.001-0.003
0.028-0.035
0.055-0.063
0.063-0.071
(6.98-7.00)
(0.03-0.08)
(0.70-0.90)
(1.40-0.60)
(1.60-1.80)
4-163
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