TM 55-4920-384-13&P
While the engine is partly or fully dismantled, all of
Low grade of gasoline.
the parts should be thoroughlv cleaned. Remove all
--
Engine overloaded.
accumulated dirt between the fins.
Restricted cooling air circulation.
If it is desired to disassemble the engine, the fol-
lowing order should be substantially adhered to. As
Part of air shroud removed from engine.
disassembly progresses, the order may be altered
Dirt between cooling fins on cylinder or head,
somewhat if desired, as will be self-evident to the
mechanic. Reassembly of the engine should be made
Engine operated in confined space where cooling air
in the reverse order.
is continually recirculated, consequently becoming
too hot.
TESTING REBUILT ENGINE
Carbon in engine.
An engine that has been completely overhauled, such
Dirty or incorrect grade of crankcase oil.
as having the cylinders rebored and fitted with new
p i s t o n s , rings and valves, should go through a
Restricted exhaust.
thorough "run-in" period, before any amount of load
Engine operated while detonating due to low octane
is applied to the engine.
gasoline or heavy load at low speed.
The engine should be started and allowed to run for
about one-half hour, at about 1200 to 1400 R.P.M.
ENGINE KNOCKS
without load. The R.P.M. should then be increased
Poor grade of gasoline or of low octane rating. See
to engine operating speed, still without load, for an
`Fuel', Page 9.
additional three and one-half to four hours.
Engine operating under heavy load at low speed.
The proper "running-in" of the engine will help to
establish polished bearing surfaces and proper clear-
Carbon or lead deposits in cylinder head.
ances between the various operating parts and thus
Spark advanced too far. See `Magneto Timing', Page
add years of trouble free service to the life of the
13.
engine.
Loose or burnt out connecting rod bearing,
`Engine overheated due to causes under previous
ACCESSORIES
heading.
The air cleaner, oil filter, magneto, and if an electric
Worn or loose piston pin.
starter and generator are used, these should be re-
moved first. Clean and repair before reassembly.
ENGINE BACKFIRES THROUGH CARBURETOR
Remove clutch or clutch reduction unit if engine is
equipped with either of these accessories.
Water or dirt in gasoline.
Engine cold.
Poor grade of gasoline.
SHEET METAL HOUSE
Sticky inlet valves. See `Valves', Page 20,
On power units; engine which are enclosed in a
sheet metal house, remove the muffler end canopy
Overheated valves.
first. Disconnect air cleaner, choke, governor control
Spark plugs too hot.
and instrument wires at the front house panel. The
front panel can be removed as part of the flywheel
Hot carbon particles in engine.
shroud, as explained in the following paragraphs of
disassembly.
DISASSEMBLY AND REASSEMBLY
OF MVG4D ENGINE
FLYWHEEL
Engine repairs should be made only by a mechanic
After the flywheel screen has been removed, the fly-
who has had experience in such work. When dis-
assembling the engine it is advisable to have several
wheel nut and the generator drive pulley should be
boxes available so that parts belonging to certain
taken off. Then as shown in Fig. 15, the flywheel
can be removed from the crankshaft.
groups can be kept together, such as, for instance,
the cylinder head screws, etc. Capscrews of various
Take a firm hold on the flywheel fins, pull outward
lengths are used in the engine, therefore great care
and at the same time strike the end of the crankshaft
must be exercised in reassembly so the right screw
with an aluminum hammer. See Fig. 15. The flywheel
will be used in the proper places.
will slide off the taper of the crankshaft. Do not use
Tighten the cap screws and nuts of the manifolds,
a hard hammer as it may ruin the crankshaft and bear-
cylinder heads, gear cover, oil pan, connecting rods,
ings. When reassembling the flywheel, be sure the
cylinder blocks, main bearing plate and the spark
Woodruff key is in position on the shaft and that the
keyway in the flywheel is lined up accurately with
plugs to the specified torque readings indicated in
the key.
the following paragraphs of reassembly.
D-16
