Air Shrouding; Disassembly And Reassembly Of Vh4D Engine; Testing Rebuilt Engine; Flywheel - Wisconsin VH4D Repair Manual

Loose or burnt out connecting rod bearing.
Engine overheated due to causes under previous
heading.
Worn or loose piston pin.
ENGINE BACKFIRES THROUGH CARBURETOR
Water or dirt in gasoline.
Engine cold.
Poor grade of gasoline.
Sticky inlet valves. See 'Valves', Page 22.
Overheated valves.
Spark plugs too hot. See 'Spark Plug', Page 15.
Hot carbon particles in engine.
DISASSEMBLY AND REASSEMBLY
OF VH4D ENGINE
Engine re, pairs should be made only by a mechanic
who has had experience in such work. When disassem-
bling the engine, it is advisable to have several boxes
available so that parts belonging to certain groups
can be kept together, such as, for instance, the cyl-
inder head screws, etc. Capscrews of various lengths
are used in the engine, therefore great care must be
exercised in reassembly so the right screw will be
used in the various places, otherwise damage may
result.
Tighten the capscrews and nuts of the manifolds,
cylinder heads, gear cover, oil pan, connecting rods,
cylinder blocks, main bearing plate and the spark
plugs to the specified torque readings indicated in
the following paragraphs of reassembly.
While the engine is partly or fully dismantled, all of
the parts should be thoroughly cleaned. Remove all
accumulated dirt between the fins.
If it is desired to disassemble the engine, the follow-
ing order should be substantially adhered to. As dis-
assembly progresses, the order may be altered some-
what if desired, as will be self-evident to the me-
chanic. Reassembly of the engine should be made in
the reverse order.
TESTING REBUILT ENGINE
Proper break-in will lead to trouble-free operation and
increased engine life. The factory test given to a new
engine is not sufficient to establish the polished bearing
surfaces which are so necessary for good performance
and long engine life. There is no quick way to force the
establishment of good bearing surfaces, and these can
only be obtained by running a new engine carefully and
under reduced speeds and loads for a short period of
time. Run the engine for a half hour without load at low
idle speed (1000 to 1200 R.P.M.). The speed should
then be increased gradually, to engine operating r.p.m.
still without load, for an additional two hours. If at all
possible, operate the engine at light loads for a period
totaling about eight hours, before maximum load is
applied.
ACCESSORIES
The air cleaner, oil filter, magneto, and if an electric
starter and generator are used, these should be re-
moved first.
Remove clutch or clutch reduction unit if engine is
equipped with either of these accessories.
SHEET METAL HOUSE
On power units, remove the muffler and canopy first.
Disconnect air cleaner, choke, governor control and
instrument wires at the front house panel. The front
panel can be removed as part of the flywheel shroud,
as explained in the following paragraphs of dis-
assembly.
FLYWHEEL
After the flywheel screen has been removed, drive
out the starting crank pin in the crankshaft and re-
move the flywheel nut and washer.
The flywheel is mounted to a taper on the crankshaft.
Take a firm hold on the flywheel fins, pull outward
and at the same time strike the end of the crankshaft
with a babbitt hammer, see Fig. 18. The flywheel
will slide off the taper of the crankshaft. Do not use
a hard hammer as it may ruin the crankshaft and bear-
ings. When reassembling the flywheel, be sure the
Woodruff key is in position on the shaft and that the
keyway in the flywheel is lined up accurately with
the key.
AIR SHROUDING
To disassemble air shrouding, refer to Fig. 19. First
remove cylinder head covers and the screws mount-
Fig. 18
18