Adapter Removal; Adapter Installation; Engine Fuel System; Carburetor Removal And Installation - Cessna 150 STANDARD Service Manual

11-31. ADAPTER REMOVAL. (See figure 11-4.)
a. Remove filter can as outlined in paragraph 11-
30.
NOTE
A special wrench adapter (Part No. SE709)
for the adapter nut, is available from the
Cessna Service Parts Center, or one may
be made as shown in figure 11-5.
b. Note angular position of adapter, then remove
safety wire and loosen adapter nut.
c. Unscrew adapter and remove adapter from en-
gine. Discard adapter a-ring.
11-32. DISASSEMBLY, INSPECTION, AND ASSEM-
BLY, Figure 11-4 shows the relative position of
the internal parts of the filter adapter and may be
used as a guide during installation of parts. The by-
pass valve is to be installed as a complete unit, with
the valve being staked three places. A new helio-
type thread insert in the adapter may be installed
although special tools are required. Follow instruc-
tions of the tool manufacturer for their use. Inspect
threads on adapter and in engine for damage. Clean
adapter in solvent and dry with compressed air.
Ascertain that all passages in the adapter are open
and free of foreign material. Also, check that by-
pass valve is seated properly.
11-33. ADAPTER INSTALLATION.
a. Assemble adapter nut and new a-ring on adapter
in sequence illustrated in figure 11-4.
b. Lubricate a-ring on adapter with clean engine
oil. Tighten adapter nut until a-ring is centered in
its groove on the adapter.
c. Apply an anti-seize compound sparingly to the
adapter threads, then simultaneously screw adapter
and adapter nut into engine until a-ring seats against
engine boss without turning adapter nut. Rotate
adapter to approximate angular position noted during
removal of adapter. Do not tighten adapter nut at
this time.
d. Temporarily install filter assembly on adapter,
and position so adequate clearance with adjacent
parts is attained. Maintaining this position of the
adapter, tighten adapter nut to 50-60 lb-ft (600-700
lb-in) and safety. Use a torque wrench when tighten-
ing adapter nut.
e. USing new gaskets, install filter assembly as
outlined in paragraph 11-30. Be sure to service
engine oil system.
11-34. ENGINE FUEL SYSTEM.
11-35. The engine is equipped with a carburetor
mounted at the lower side of the engine. The car-
buretor is of the plain-tube fixed-jet type, and has
such features as an enclosed accelerating pump
mechanism, simplified fuel passages to prevent
vapor locking, idle cut-off to prevent starting of
the engine accidentally, and manual mixture control
for leaning. For overhaul and repair of the car-
buretor refer to the manufacturer's overhaul and
repair manual.
11-36. CARBURETOR REMOVAL AND INSTALLA-
TION.
a. Place fuel shut-off valve in the OFF position.
b. Remove engine cowling and drain fuel strainer.
c. Disconnect flexible ducts from each side of in-
take airbox.
d. Disconnect carburetor heat control at arm on
airbox. Remove clamp securing control to airbox.
e. Remove bolts and screws attaching airbox to
carburetor and engine bracket.
f. Disconnect throttle and mixture controls from
arms on carburetor. Note EXACT position, size and
number of washers and spacers for reference on re-
installation.
g. Disconnect and plug fuel line at carburetor.
h. Remove nuts and washers attaching carburetor
to intake manifold. Remove carburetor and mount-
ing gasket.
i.
Reverse the preceding steps for reinstallation.
Use new gaskets when installing carburetor. Rig
controls in accordance with paragraphs 11-52, 11-531
and 11- 54. Check carburetor throttle arm to idle
stop arm attachment for security and proper safety-
ing at each normal engine inspection in accordance
with figure 11-8.
11-37. IDLE SPEED AND MIXTURE ADJUSTMENT
should be accomplished after the engine has been
warmed up. Since idle rpm may be affected by idle
mixture adjustment, it may be necessary to readjust
idle rpm after setting the idle mixture correctly.
a. Set the throttle stop screw to obtain between
575 and 600 rpm, with throttle control pulled full out
against idle stop.
NOTE
Engine idle speed may vary among different
engines. An engine should idle smoothly,
without excessive vibration, and the idle
speed should be high enough to maintain
idling oil pressure and to preclude any pos-
sibility of engine stoppage in flight when the
throttle is closed.
b. Advance throttle to increase engine speed to
1000 rpm.
c. Pull mixture control knob slowly and steadily
toward the idle cut-off position, observing tachom-
eter, then return control full in position before
engine stops.
d. Adjust mixture adjusting screw at upper end of
carburetor intake throat to obtain a slight and
momentary gain of 25 rpm maximum at 1000 rpm
engine speed as mixture control is moved from full
in toward idle cut-off position. Return control to
full rich to prevent engine stoppage.
e.
If
mixture is set too LEAN, engine speed will
drop immediately, thus requiring a richer mixture.
Turn adjusting screw out (counterclockwise) for a
richer mixture.
f.
If
mixture is set too RICH, engine speed will
increase above 25 rpm, thus requiring a leaner
mixture. Turn adjusting screw in (clockwise) for a
leaner mixture.
Change 1
11-17