TM 55-4920-384-13&P
Dieseling, is caused by the carbon and lead deposits
WARM-UP PERIOD
in the cylinder head being heated up to such an extent
The engine should be allowed to warm up to operat-
that they continue to fire the engine and keep it run-
ing temperature before the load is applied. This re-
ning after the ignition has been shutoff. By idling the
quires only a few minutes of running the engine at a
engine, as previously mentioned, the carbon and lead
moderate speed.
deposits cool off, break up and will blow out thru the
exhaust. If engine should continue to diesel, by sud-
Racing an engine or gunning it, to hurry the warm-up
denly opening up the throttle wide and at the same
period, is very destructive to the polished wearing
time shutting off the ignition, the engine will stop.
as the proper oil film on these various surfaces can-
AIR CLEANER
not be established until the oil has warmed up and
become sufficiently fluid. This is especially impor-
The air cleaner is an essential accessory, filtering
tant on new engines and in cool weather.
the air entering the carburetor, and thereby prolong-
ing the life of the engine.
Racing an engine by disconnecting the governor, or by
doing anything to interfere with the governed control
engine speed, is extremely dangerous. Quite naturally
the operator of the engine desires to get all possible
power out of an engine, and the engine manufacturer
does his best to supply this want, but if all of this
power is used merely to speed up the engine, without
any load being imposed upon it, dangerously high
speeds will result.
The governor is provided as a means for controlling
the engine speed to suit the load applied, and also
a s a safety measure to guard against excessive
speeds, which not only overstrain all working parts,
but which might cause wrecking of the engine and
possible injury to bystanders.
All parts of the engine are designed to safely with-
stand any speeds which might normally be required,
but it must be remembered that the stresses set up in
rotating parts increase with the square of the speed.
That means that if the speed is doubled, the stresses
will be quadrupled, and if the speeds are trebled, the
stresses will be nine times as great.
Remove the bowl from the air cleaner, as illustrated
in Fig. 9. Fill the bowl to oil level line with the
Strict adherence to the above instructions cannot be
same grade of oil as used in the crankcase. Detailed
too strongly urged, and greatly increased engine life
instructions are printed on the air cleaner.
w i l l result as a reward for these easily applied
recommendations.
The air cleaners must be serviced frequently, de-
pending on the dust conditions where the engines are
operated. When the oil in the bowl becomes dirty, it
STOPPING ENGINE
should be removed and replaced with new oil. This
servicing will vary from a few days of operation in
Depress magneto switch to stop engine. With spring
comparatively clean conditions to twice a day in
button ground switch, hold stop button in depressed
dusty conditions.
position until engine stops.
If the engine has been running hard and is hot, do not
Operating the engine under dusty conditions
stop it abruptly from full load, but remove the load
without oil in the air cleaner or with dirty oil,
and allow engine to run idle at 1000 to 1200 R.P.M
may wear out cylinders, pistons, rings and
for three to five minutes, depending on how hot the
b e a r i n g s in a few days time, and result in
engine has been. This will reduce the internal tem-
costly repairs.
perature of the engine much faster, minimize valve
warping, and of course the external temperature, in-
.
At least once a year the air cleaner should be re-
eluding the manifold and carburetor will also reduce
moved from the engine, and the element which is not
faster, due to air circulation from the flywheel.
removable, should be washed in a solvent to clean
Two main troubles resulting from abrupt shutting off
out the accumulated dust and dirt.
a hot engine are vapor lock and dieseling. Vapor lock
If a collector type pre-cleaner is used on the top of
will prevent the flow of fuel in the fuel lines and
the air cleaner, Fig. 10, it should be emptied of
carburetor passages, which will result in hard start-
accumulated dirt frequently, depending on dust con-
ing of the engine. This can be overcome by choking
ditions. Do not use oil or water in pre-cleaner. This
the engine when cranking or waiting until the engine
should be kept dry.
has cooled off sufficiently to overcome the vapor lock.
D-11
