ENGINE
Paragraph
Description and data 39
Tune‐up 40
Replacement of head gasket 41
Carbon removal 42
Valve tappet adjustment 43
Replacement of oil feed pump 44
39. DESCRIPTION AND DATA.
=a. Description.= This 2‐cylinder, V‐type, air‐cooled gasoline engine
of L‐head design operates on the 4‐stroke, 4‐cycle principle. Flywheel
and connecting rod assemblies operate on roller bearings. Engine is
fitted with low‐expansion aluminum alloy, cam‐ground, horizontally
slotted pistons and with deep‐finned aluminum cylinder heads. As viewed
from left side of vehicle (drive chain side), rotation of engine is
counterclockwise.
=b.= Lubrication system is of dry‐sump type, in which oil supply
is maintained in a tank away from engine. Oil is circulated by a
supply feed pump and a scavenger, return pump. This oil circulating
system plays a most important part in cooling the engine as well as
lubricating it.
=c. Data.=
Type of engine 2‐cylinder, V‐type, L‐head,
air‐cooled
Cylinder bore 2-3/4 in.
Stroke 3-13⁄16 in.
Piston displacement 45.12 cu in.
Compression ratio 5.0:1
Horsepower (N.A.C.C. Rating) 6.05
Engine number (serial), left side of engine base, just below front
cylinder.
40. TUNE‐UP.
=a.= Tune‐up consists of making correct adjustment to valve tappets,
circuit breaker ignition points, spark plug electrodes: checking and
correcting ignition timing; draining and flushing carburetor bowl;
cleaning and flushing gasoline strainer; cleaning muffler outlet,
servicing air cleaner, and adjusting carburetor.
(1) Valve tappet adjustment (par. 43).
(2) Circuit breaker point adjustment (par. 84).
(3) Spark plug service (par. 83).
(4) Timing ignition (par. 86).
(5) Draining carburetor bowl (par. 73).
(6) Cleaning fuel strainer (par. 72).
(7) Cleaning muffler outlet requires freeing outlet of carbon deposits,
caked dirt, oil, etc., with blade of screwdriver, or other suitable
tool. Do not enlarge outlet size when cleaning.
(8) Servicing air cleaner (par. 76).
(9) Adjusting carburetor (par. 68).
[Illustration:
A—CYLINDER BRACKET SPACERS AND WASHERS
B—CYLINDER BRACKET AND FRAME BOLT
C—CYLINDER UPPER MOUNTING BRACKET
D—SPARK CABLE CLIP
E—CYLINDER BRACKET BOLTS
F—OIL RETURN PIPE CONNECTION HOLLOW BOLT AND WASHERS
RA PD 315711
_Figure 15—Disassembly for Head Gasket Replacement_]
41. REPLACEMENT OF HEAD GASKET (fig. 15).
=a. Removal.= Refer to figure 15, illustrating necessary parts and
units to be removed to perform this operation.
(1) Remove instrument panel cover (par. 119).
(2) Remove gasoline tank and oil tank (par. 107).
(3) Remove cylinder head bracket to frame lug bolt: this will free
clamp which secures front spark plug cable. Pay particular attention
to shim washers placed between cylinder head bracket and frame lug, as
these washers must be replaced when installing cylinder head.
(4) Remove spark plug, or plugs.
(5) Remove cylinder head bolts, using head bolt wrench 41-W-1525. NOTE:
_On some 42 WLA models, plain washers (0.095-inch thick), in addition
to regular (heavy) cylinder head bolt washers, were used to prevent
cylinder head bolts from bottoming._
(6) Perform carbon removal (head only). Refer to paragraph 42.
=b. Installing Gasket and Head= (fig. 15).
(1) Clean top of cylinder. Apply a light application of grease or oil
to both sides of gasket before locating on cylinder head. Place head on
cylinder.
(2) Install head bolts, using heavy washers (also 0.095-inch thick
plain washers, if any were removed). If in doubt as to use of
0.095-inch thick washers in addition to regular washers, measure depth
of bolt holes in cylinder head. Head having hole depth of 31/32 inch
must use the 0.095-inch thick washers in addition to regular washers.
Head having bolt hole depth of 1-1/16 inch does not require the
0.095-inch thick washers.
(3) Install cylinder frame bracket with the two long bolts, special
(spool‐shaped) spacers, and flat washers. The spacers go between
cylinder heads and frame bracket. A flat washer goes under the head of
each long cylinder bolt, above the bracket; some engines may have flat
washers between the spacers and the bracket.
(4) Tighten head bolts evenly to ensure a tight cylinder head joint.
Use head bolt wrench 41-W-1525, first turning down bolts just snug,
then tightening each bolt 1/8 to 1/4 turn at a time, until all are
securely tightened. If torque wrench is available, tighten head bolts
to 60 foot‐pounds minimum, 65 foot‐pounds maximum tension when engine
is cold.
42. CARBON REMOVAL.
=a.= At time cylinder head is removed for gasket replacement, carbon
must be removed from head only.
43. VALVE TAPPET ADJUSTMENT (fig. 16).
=a. Adjust Tappets with Engine Cold.= Before loosening valve spring
covers, a light application of oil around top edge of each cover will
facilitate raising cover without damage to seal packing.
(1) Loosen valve spring covers; use tappet and valve cover wrench
41-W-3617.
(2) Before checking or adjusting tappet clearance, make sure valve is
seated and that tappet is at lowest position, by turning engine ahead
until like tappet (inlet or exhaust, whichever one is being adjusted)
in the other cylinder is at highest position (valve fully open). Inlet
valves are located nearest the carburetor manifold.
[Illustration: RA PD 310211
_Figure 16—Valve Tappet Adjustment_]
(4) Loosen adjusting screw lock nut (“2,” fig. 16) slightly before
turning adjusting screw (fig. 16).
(5) Adjust inlet valve tappets to 0.004-inch minimum, and 0.005-inch
maximum clearance between valve stems and tappet (“1” and “4,” fig.
16). Use thickness gage to determine clearance; recheck (correcting if
necessary) clearance after lock nut has been securely tightened.
(6) Adjust exhaust valve tappets to 0.006-inch minimum, and 0.007-inch
maximum clearance between valve stems and tappet. Use thickness gage to
determine clearance; recheck (correcting if necessary) clearance after
lock nut has been securely tightened.
(7) Before turning down valve spring covers, inspect paper gasket
between each cover and tappet guide. If broken or damaged, fit a new
gasket to prevent oil leak. Turn down and securely tighten valve spring
covers.
[Illustration: RA PD 315712
_Figure 17—Oil Pump Removed_]
44. REPLACEMENT OF OIL FEED PUMP (fig. 17).
=a. Removal.=
(1) Disconnect oil tank feed pipe at oil tank. Install nipple cap on
tank nipple to prevent oil from running out, or drain tank. Disconnect
oil feed pipe from oil pump nipple.
(2) Oil pump is secured to engine gear case cover by one hexagon head
bolt and three nuts. Two of the nuts are extra long to provide wrench
clearance, and their location should be noted so they will be put back
where they belong when reinstalling pump. After removing screw and
nuts, remove pump. Unless a new pump gasket is available, take care
not to damage or break the old one, as this is a very special gasket
concerning both thickness and holes provided for oil channels. A
“homemade” gasket may put oiling system completely out of commission.
=b. Installing Oil Pump.=
(1) Clean surface of pump body mounting on gear case cover and see that
gasket is in good condition. Clean face of oil pump body.
(2) Start pump on mounting studs, turn engine slowly and press lightly
against pump until driving dogs on end of cam gear shaft line up with
and drop into driving slot in oil pump rotor.
(3) Insert hexagon‐head bolt and lock washer, and install the three
lock washers and nuts (two are long extension nuts) on pump mounting
studs. Make sure to replace the two extra long nuts on the studs from
which they were originally removed.
(4) Tighten mounting bolt and three nuts securely.
(5) Connect oil feed pipe to oil pump nipple. Remove nipple cap from
tank nipple and connect upper end of oil feed pipe to this nipple.
Tighten nipple nuts securely.