1953 JEEP DJ compression ratio

'Jeep*
UNIVERSAL
SERIES
SERVICE
MANUAL

D D-l 13. HURRICANE
F4
ENGINE SPECIFICATIONS

MODEL:
ENGLISH
ENGINE:

Type

Number of Cylinders

Bore
Stroke
Piston Displacement...........
Bore
Spacing (center to center): 1 and 2, 3 and 4
2 and 3

Firing
Order Compression Ratio Compression Pressure... .
Number of Mounting Points:

Front
Rear

Horsepower (SAE)
Horsepower (Max Brake) Maximum Torque @
2000
rpm.
PISTONS:

Material
Description

Length
,.
Diameter (near
bottom
of
skirt).

Weight.
Clearance
Limits:
Piston-To-Cylindcr
Bore

Ring
Groove Depth:
No. 1 and 2 Ring No. 3 Ring

Ring
Groove Width:
No. 1 Ring No. 2 Ring
No. 3 Ring
Piston Pin Hole Bore
Cylinder
Bore — Standard.....
—
max. out of round
F-Head

4

W

134.2 cu. in.

3.437"

4.938"

1-3-4-2
6.7:1
120 to 130 psi.
2
1
15.63

@
4000
rpm. 114 lb-ft. 75

-
max. taper..

-
max. rebore.

PISTON RINGS:
Function:

No. 1 and 2 No. 3. .

Material:

No. 1. .
No. 2 and 3

Width;
No. 1 and 2
No. 3. . . .

Gap
(Std. to .009 Cyl. Bore).
Thickness:
No. 1 and No. 2 Rings....
No. 3 Ring
Side Clearance in Groove:
No. 1 Ring No. 2 Ring
No. 3 Ring

PISTON
PINS:
Material

Length
Diameter

Type

Clearance
in Piston
(selective
fit).
Aluminum
Alloy

Gam
Ground, T-slot, Tin Plated

3.1225*
to
3.1245*
13.5 oz.
Selective Feeler Fit
.1593" to .1655"
.1693" to .1755"
.0955" to .0965" .095" to .096"
1875" to .1885" .760" to .770"

3.125"
to
3.127"
.005" .005" .040"
Compression
Oil

Cast
Iron,
Chrome-plated Face
Cast
Iron

.007" to .017"
.134" to .144" .115" to .125"
.002" to .004"
.0015" to .0035" .001" to .0025"

SAE
1016 Steel
2.781"
.8119"

Locked
in Rod

.0001"
to .0003"
METRIC

7,937
cm.

11,112
cm. 2199 cm*

8,729
cm.

12,542
cm.
8,4 a 9,2 kg-cm2
15,77 kg-m.
9,525
cm.

7,9311
a
7,9362
cm.

382,7
gr.

4,046
a
4,203
mm.
4,300
a
4,457
mm.

2,4257
a
2,4511
mm. 2,413 a
2,438
mm.

4,7625
a
4,7879
mm.
19,304
a
19,558
mm.
7,9375
a
7,9425
cm.

0,1270
mm.

0,1270
mm.
1,0160
mm.
2,38 mm.
4,76 mm.
0,178 a
0,432
mm.

3,403
a
3,657
mm. 2,821 a 3,175 mm.
0,051 a 0,102 mm.
0,038
a
0,088
mm.

0,025
a
0,063
mm.

70,637
mm.

20,6223
mm.

0,0025
a
0,0076
mm. 71

Dl

DAUNTLESS
V-6
ENGINE
DM.
GENERAL

This
section describes service and repair of the
Dauntless V-6 engine. The
engine
code
number shown in
Fig.
A-4 is provided to identify the Daunt­

less
V6-225 engine. The meaning of the coded letters and numbers that are stamped on the right front face of the crankcase, just below the rocker
arm
cover,
between
exhaust manifold ports, is given
below.
Letter
to
Designate
Market

M
—
Military
E
—
Export

D
— Domestic
Letter
to
Designate
Year
Built

N
— 1967
P
— 1968

R
— 1969
S
— 1970

T
— 1971

Letter
to Designate
Engine
and Compression
Ratio

H—V6-225
9.0 to 1
C.R.
(2 Bbl.
Carb.)
Y—V6-225
9.0 to 1
C.R.
Marine
(Low
Profile)
(2
Bbl.Carb.)
Z—V6-225
9.0 to 1
C.R.
Marine
(High
Profile)
(2 Bbl.
Carb.)

K—V6-225
7.6 to 1
C.R.
(2 Bbl.
Carb.)
L—V6-225
7.4 to 1
C.R.
(2 Bbl.
Carb.)

Market

Domestic
—

Year
"1967"
Engine
J

Day

Plus Chg. If
Any-
Service Engine "S"
Short
Block
"R" -Oversize Bores "B"
Undersize Crank

&
"A"

Rod
Bearings

The
identifying letter or letters follow the
engine
letters are decoded as follows:
A—.010"
Undersize
Main
and Connecting Rod
Bearings

B—.010"
Oversize Pistons

AB—Combination
of A and B
S—Service
Engine

R—Short
Block

All
disassembly and assembly procedures are pre­ sented in logical order, assuming a complete
engine

overhaul
with
engine
removed from the vehicle.

However,
many of
these
procedures can also be
performed as on-vehicle services if vehicle or
engine
components are removed to gain access to parts
involved.

Note:
Some
engines
are equipped with an exhaust
emission control system. Service information on
the components of this system is given in sec­ tion F2.

Dl-2.
ENGINE
DESCRIPTION

The
Dauntless V-6
engine
has a displacement of
225 cubic inches. It has a compression ratio of
9.0 to 1, which permits use of regular-grade
gaso­

line.
See
Figs.
Dl-1 and Dl-2.

The
cylinder block is made of cast
iron.
Two banks
of cylinders (three cylinders per bank) are cast at a
90-degree
angle. The lower part of the cylinder-

block
extends
below the centerline of the
crank­
shaft, forming a continuous flat surface with the

rear
crankshaft main bearing cap and the timing

chain
cover.
This
design allows installation of an
oil
pan with a
one-piece
gasket. The cylinders in
the left bank (as viewed from the driver's seat) are
numbered
1-3-5,
from front to
rear.
The cylinders

in
the right bank are numbered
2-4-6,
from front
to
rear.

The
crankshaft is supported in the cylinder block
by four steel-backed full-precision bearings, all of

which
have an identical diameter.
Crankshaft
main bearings are numbered 1 to 4, front to
rear.
The

thrust
bearing is flanged to maintain crankshaft position and to compensate against crankshaft end

thrust
The No. 2 bearing is the thrust bearing.

The
crankshaft is counterbalanced by weights,
which
are cast integral with the
crank
cheeks. The

weights
are shaped to a contour which
gives
mini­
mum
clearance with cylinder barrels and piston

skirts
to conserve space.

Connecting
rods have I-beam sections with
bosses

on each side. Metal is removed, as required, to secure correct weight and balance. The lower end
of each connecting rod has a steel-backed preci­
sion bearing. The piston pin is a press fit into the upper end. The outer ends of the piston pin

are
a slide fit in the piston
bosses.

The
full-skirted, aluminum alloy pistons are cam ground and tin plated. Two compression rings and
one oil control ring are installed above the piston
pin.
The cast iron compression rings in the two

upper
grooves
of the piston have a
groove
or bevel cut around the inner
edge
on one side. The
top compression ring is installed with this
groove
or
bevel up. The lower compression ring is installed

with
bevel down. The oil
ring,
in the lower groove,
consists of two thin steel
rails
separated by a

spacer.
It is backed by a hump-type spring-steel
expander.

V-6
engine
cylinder heads are made of cast
iron.

Their
valve
guides
are cast integrally. Right and left cylinder heads are identical and interchange­
able. In service, however, it is
good
practice to
install
the cylinder heads on the side from which
they were removed.

The
valves are in line in each head, at an angle
10°
above the centerline of the cylinder bores.

Each
valve has a spring strong enough to ensure
positive valve seating throughout the operating speed range of the engine. The valve rocker arm
mechanism is protected by a
sheet
metal cover.
This
cover is seated on a raised surface of the
cylinder
head. It is gasketed to prevent oil leaks.

The
rocker arms for each bank of cylinders are mounted on a tubular steel shaft, supported on
the cylinder head by brackets. The rocker arms
are
made of aluminum. They have inserts at the

push
rod socket and the valve stem contact face.

The
camshaft is located above the crankshaft be­
tween the two cylinder banks; it is supported in
four steel-backed babbitt-metal bearings. The cam­ shaft is driven at one-half crankshaft speed by
sprockets and a single outside-guide type chain.

Hydraulic
valve lifters and
one-piece
push rods operate overhead rocker arms and valves of both

banks
of cylinders from a single camshaft.
This

system requires no lash adjustment during assem­
bly
or in service.

In
addition to its normal function of a cam follower,
each hydraulic valve lifter also serves as an auto- 76

Pi

DAUNTLESS
¥-6
ENGINE
which
would cause rings to seat improperly or have
excessive clearance in
ring
grooves. Damaged or
faulty
pistons should be replaced,
c.
Inspect bearing surfaces of piston pins and check

for
wear by measuring worn and unworn surfaces

with
a micrometer. Rough or worn pins should be
replaced.
Test fit the piston pins in piston
bosses.
Occasionally,
a pin
will
be tight due to gum or

varnish
deposits.
This
may be corrected by remov­

ing
the deposit with a suitable solvent. If piston
bosses
are worn out-of-round or oversize, the piston

and
pin assembly must be replaced. Oversize pins
are
not
practical,
since the pin must be a press fit
in
the connecting rod bore. Piston pins must fit the
piston with an easy finger push at
70°F.
[21°C.].

They
should have .0004" to .0007"
[0,0178
a
0,0102
mm.] clearance.

Dl-46.
Piston Fitting

If
cylinder bores are rebored or heavily honed,
new and possibly oversize diameter pistons must be
installed.
A new piston must be fitted to its cylinder

bore.
A satisfactory method of fitting pistons is as
follows.

a.
Expand
a
telescope
gauge
to fit the cylinder bore at right angles to the piston pin and
between
1
Vi"
to 2" [3,7 a 5,1 cm.] from the top.

b.
Measure diameter of the piston to be fitted, as
shown in
Fig.
Dl-15. The piston must be measured

at
right angles to the piston pin, W [6,3 mm.] below the oil
ring
groove. The piston must be be-
FIG.
Dl-15—MEASURING
PISTON

1—90°
tween .001" and .0015" [0,025 a
0,038
mm.]

smaller
than the cylinder bore.

Note:
Both cylinder block and piston must be at

very
nearly the same temperature when measure­
ments are made or
errors
due to expansion
will
occur.
A difference of 10°F.
[5,6°C]
between
parts
is sufficient to produce a variation of .0009"
[0,0023
mm.].

The
pistons are cam-ground, which means that the
diameter at a right angle to the piston pin is
greater
than the diameter
parallel
to the piston

pin.
When a piston is checked for size, it must be
measured
with a micrometer applied to the
skirt

along a line
perpendicular
to axis of the piston pin.

Dl-47.
Piston Ring Fitting

When
new piston rings are to be installed without

reboring
cylinders,
the glazed cylinder walls should
be slightly dulled. However, cylinder bore diameter
should
not increase more than necessary.
Cylinder

walls
should be honed with the finest grade of
stone
to remove any glaze.
New compression rings must be checked for clear­ ance in piston
grooves
and for gap in cylinder bores;
however, the flexible oil rings are not checked for gap. The cylinder bores and piston
grooves
must
be clean, dry, and free of carbon and
burrs.

With
rings installed on piston, check clearance in
grooves
by inserting feeler
gauge
between
each
ring

and
its lower
land.
Any
ring
groove
wear
will
form

a
step
at inner portion of the lower
land.
If the
piston
grooves
have worn enough that relatively

high
steps
exist on the lower lands, the piston
should
be replaced because the
steps
will
interfere

with
proper operation of new rings and the
ring
clearances
will
be excessive. Piston rings are not

furnished
in oversize widths to compensate for
ring
groove
wear.

When
fitting new rings to new pistons, the side

clearance
of the compression rings should be .002" to .0035"
[0,051
a
0,089
mm.] for number one (1)

ring,
.003" to .005" [0,076 a 0,127 mm.] for number
two (2)
ring,
and side clearance of the oil
ring
should
be .0015" to .0085" [0,038 a
0,220
mm.].

To
check the end gap of a compression
ring,
place

it
in the cylinder in which it
will
be used, square

it
in the bore by tapping with the lower end of
a
piston, then measure the gap with a feeler
gauge.

A
compression
ring
should not have
less
than .015"
[0,381
mm.] gap when placed in cylinder

bore.
If gap is
less
than specified value, file the
end of the
ring
carefully with a fine file to obtain

proper
gap.

Dl-48.
Piston and Connecting Rod Assembly

Note:
A connecting rod can spring out of alignment

in
shipping or handling. Always check a new con­
necting rod for misalignment before installing pis­
ton and pin.

a.
If a new connecting rod is to be installed, check
its alignment with an accurate rod alignment fix­

ture.

b.
If the piston and connecting rod assembly is
to be installed in the left cylinder bank, it must be assembled as shown in
Fig.
Dl-16. If the piston and
connecting rod assembly is to be installed in the
right
cylinder bank, it must be assembled as shown
in
Fig. Dl-17.
Note
that
these
two assemblies are

mirror-images
of each other.

c.
Lubricate
piston pin to avoid damage when

pressing
through the connecting rod.

d.
To install piston pin in piston and connecting

rod,
use
Tool
Set W-338.
Install
collar J-6047-5,
spring
J-6047-3, and pilot J-6047-20 into the base

support
J-6047-1 and place in
arbor
press. Using

driver
J-6047-4 press piston pin into piston and 88

Dl

'Jeep5
UNIVERSAL
SERIES
SERVICE
MANUAL

FIG.
Dl-16—LEFT
BANK
PISTON

AND
ROD
ASSEMBLY
(No.
1-3-5)

1—
Oil
Spurt Hole Up
2— Boss on Rod and Cap
Rearward

3—
Notch on Piston
Forward

12716

FIG.
Dl-17—RIGHT
BANK
PISTON
AND
ROD
ASSEMBLY
(No. 2-4-6)
1—
Oil
Spurt Hole Up
2— Boss on Rod and Cap
Forward

3—
Notch on Piston
Forward

14355

FIG.
Dl-18—-PISTON
PIN
INSTALLATION
connecting rod until pin
bottoms.
Refer to Fig.

Dl-18.

e.
Remove piston and connecting rod assembly
from
press. Rotate piston on pin to be certain that

pin
was not damaged during the pressing operation. 13297
1—
Driver

2— Piston Pin

3—
Piloi
4—
Spring

5—
Collar

6—
Support
Base
FIG.
Dl-19—PISTON
RINGS

1—
Compression
Rings
2—
Expander

3—
Rail

4—
Spacer

5—
Oil
Ring
f.
Install
piston rings on piston as follows. Refer
to Fig. Dl-19. Position ends of piston ring expander
over piston pin.
Install
oil ring
rail
spacer and
oil
ring
rails.
Position
gaps
in rails upward on same
side of piston as oil spurt
hole
in connecting rod.
Install
compression rings in upper two grooves. If

a
single chrome-plated compression ring is used,
the chrome ring must be installed in the top groove.

Note:
All compression rings are marked with a
dimple, a letter
"T",
a letter
"O",
or word
"TOP"

to identify the side of the ring which must face

toward
the top of the piston. If a single chrome-
plated compression ring is used, the chrome ring must be installed in the top groove.

Dl-49.
Connecting
Rod
Bearing Inspection and Fitting

a.
If connecting rod bearings are chipped or scored,
they should be replaced. If bearings appear to be
in
good
condition, check for proper
radial
clear­
ance on crankpin. If
radial
clearance
exceeds
.003" [0,076 mm.], it is advisable to install a new

bearing.
However, if bearing appears to be in
good

condition and
does
not cause noise, it
will
not be mandatory to replace it.
Radial
clearance can be
checked either with Plastigage, as described in Par.
Dl-42,
or with a strip of feeler or shim stock, as
described in Par. Dl-43. Connecting rod bearings
differ from crankshaft main bearings in that their
desired
radial
clearance is .0002" to .0023" [0,005

a
0,0585
mm.] and their cap
bolts
and nuts are to be hand torqued to a 30 to 40 lb-ft. [4,1 a 5,5
kg-m.] torque.
b. After each connecting rod bearing has been

properly
fitted, attach bearing cap
loosely
with
two cap
bolts
and nuts to keep parts of each as­
sembly
together
until installation. 89

Dl

DAUNTLESS
V-6
ENGINE
E-105.
DAUNTLESS V-6 ENGINE SPECIFICATIONS

ENGINE:
Type

Number
of Cylinders Valve Arrangement
Bore
Stroke

Piston
Displacement

Firing
Order Compression Ratio

Number
of
Mounting
Points:

Front.

Horsepower
(SAE)

Horsepower
(max. brake) Torque (max.
2400
rpm.)
Cylinder
Numbers,
Front to Rear:
Right Bank

Left
Bank
Cylinder Block Material
Cylinder Head Material English

90°
V-6 6

In
head
3.750"
3.400"

225 cu. in.
1.6.5.4.3.2

*9.0:1

2

33.748

160 @
4200
rpm. 235
lb-ft.

2, 4, 6 1, 3, 5

Cast
Iron
Cast
Iron Metric

9,525
cm.

8,636
cm. 3,69 ltr.

32,49
kg-m.

PISTONS:
Material
Description Clearance Limits:
Top
Land
Skirt
Top

Skirt
Bottom

Ring Groove Depth*. No. 1
No. 2, 3
Cylinder Bore: Out-of-Round (max.). Taper (max.)
Cast
Aluminum Alloy

Cam
Ground, Tin Plated

.0125"
to
.0295" .0005"
to
.0011"

.0005"
to
.0011"

.1880"
to
.1995"
.1905"
to
.1980"

.003"
.005" 0,318 a
0,749
mm.

0,0127
a
0,0279
mm.

0,0127
a
0,0279
mm.

4,775
a
5,067
mm.
4,839
a
5,029
mm.

0,076
mm. 0,127 mm.

PISTON
RINGS:
Function: No. 1 and No. 2 Ring.. No. 3 Ring
Location
Material: No. 1...
No. 2 No. 3.

Oil
Ring Type
Oil
Ring Expander
Width: No. 1
No. 2. .
No. 3

Gap:
No. 1 and No. 2
No. 3

Side
Clearance in Groove: No. 1
No. 2
No. 3 Compression

Oil
Control

Above
Piston
Pin

Iron,
Chrome Plated
Iron,
Pre lubricated
Steel

Dual
Rail,
With Spacer Humped Ring

.0785"
to
.0790" .0770"
to
.0780"
.181" to .187"
.010" to .020"
.015" to .035"
.002" to
.0035"
.003" to .005"

.0015"
to
.0085"
1,993 a
2,007
mm.
1,956 a 1,981 mm. 4,60 a 4,75 mm.
0,25 a 0,51 mm.
0,38 a 0,89 mm.
0,051 a
0,089
mm.
0,076
a 0,127 mm.

0,038
a
0,220
mm.

PISTON
PINS:
Material
Length

Diameter

Type Clearance in
Piston

Clearance in
Connecting
Rod.

Distance
Offset
Toward High-Thrust
Side
of Piston.
Steel,
SAE 1018, SAE 1118

3.060"

.9394"
to
.9397"

Pressed in
Connecting
Rod
.0004"
to
.0007" .0007"
to
.0017"

.040"
7,772
cm.

23,861
a
23,868
mm.

0,0102
a
0,0178
mm.
0,0178
a
0,0431
mm.
1,016 mm.
*State
of California Exhaust Emission Control Engine 7.4 Compression Ratio.
106

FUEL
SYSTEM

14261

FIG.
E-6—CARBURETOR—
F4 ENGINE,
LATE
MODEL 1—
Choke
Clamp Bracket
2—
Throttle
Lever
and Shaft
3—
Choke
Shaft and
Lever

4—
Bowl
Vent Tube
5—
Fuel
Inlet Elbow
6—
Dash
Pot Bracket 7—
Throttle
Lever
8—
Dash
Pot Plunger
9—
Dash
Pot Assembly
10—
Lock
Nut
11— Stop Pin

1
2—Idle Mixture
Limiter
Cap
13—
Idle
Speed Adjusting Screw 14—
Fast
Idle Connecting Rod
E-11.
Float System

The
float system, Fig. E-7, consists of a float,
float
pin,
air horn gasket and the
needle
and seat assembly. These parts control the fuel level in the

carburetor
bowl, a supply being maintained for all
systems under all operating conditions. To prevent
float
vibration
from affecting the fuel level, the
inlet or float valve is spring loaded. Should the

needle
and seat
become
worn, they must be re­
placed
with a matched set, including the spring,

which
is the only way they are supplied. When
reinstalling
the float, be sure to install the float pin

with
the
stop
shoulder on the side away from the bore of the carburetor.

E-12.
Float Adjustment

Correct
float level setting is required for accurate
metering of fuel in both low- and high-speed jets.

To
set the float, remove and invert the bowl cover. Remove the bowl cover gasket. Allow the weight
of the float to rest on the
needle
and spring. Be

sure
there is no compression of the spring other

than
the weight of the float. Adjust the level by
bending the float arm lip that contacts the
needle
(not the arm) to provide specified clearance be­
tween the float and cover. The specified clearance of the float is
L74\F
[6,74 mm.] on current models
(including
Exhaust
Emission Control) and [7,93 mm.] on early models shown as A in
Fig.
E-8.
FIG.
E-7—FLOAT SYSTEM
1—
Float
and
Lever
Assembly
2—
Needle
Valve and Seat Assembly

3—
Vent

4—
Float
Bowl Cover 5—
Float
7 '.. j
io8Si
i

FIG.
E-8—FLOAT
LEVEL
GAUGING
E-13.
Low-Speed System

Fuel
for idle and early part-throttle operation is
metered through the low-speed system. The low-
speed system is illustrated in Fig.
E-9.
Liquid
fuel enters the idle well through the metering rod jet.

Low-speed
jet measures the amount of fuel for
idle and early part-throttle operation. Air-by-pass,
economizer, and idle air bleed are carefully
cali­

brated
orifices which serve to break up the liquid
fuel
and mix it with air as it
moves
through the passage to the idle port and idle adjustment screw

port.

E-14.
Idle Mixture Adjustment

Note:
The idle mixture adjustment procedure for
the late model
YF-4941S
and
YF-6115S
Carter
Carburetor
equipped with the
External
Idle

Mixture
Limiter
Cap is the same as outlined below 114

E

FUEL
SYSTEM
Note:
Do not remove pressed-in parts such as
nozzle, pump jet, or antipercolator air bleed.

j.
Remove body flange attaching screws, body flange assembly, and gasket.

k.
Remove idle-adjustment screw, spring, idle

port
rivet, throttle lever assembly, washer, fast
idle arm, throttle plate screws, throttle plate, and throttle shaft.
1. Remove throttle shaft seal by prying out seal

retainer.

Note:
Do not remove pressed-in vacuum passage

orifice.

m.
Remove choke valve screws and choke valve.

Unhook
choke spring and slide shaft from housing,
n.
Wash all parts in carburetor cleaning solution

and
blow out passages with compressed air. Do not immerse diaphragm or seals in cleaning solution.

Inspect
all parts for wear or damage. Always use
new gaskets when reassembling.

E-22.
Carburetor
Reassembly

•
Refer to Fig. E-13.

To
expedite
reassembly, it is advisable to group all

related
parts by the circuit to which they belong.

a.
Install
throttle shaft seal and retainer in flange casting.

b.
Install
fast-idle
arm,
washer, and lever assembly
on throttle shaft. Slide shaft into place and install throttle valve.

c.
Install
idle port rivet plug and idle adjusting

screw
and spring.

d.
Attach flange assembly to body casting. Use new gasket.
e.
Install
low-speed jet assembly.
f.
Early
production models install pump intake
strainer
in pump diaphragm housing and carefully
press into recess.

Note:
If strainer is even slightly damaged, a new
one must be installed.
g.
Install
pump diaphragm assembly in diaphragm housing.
Then,
install pump diaphragm spring
(lower)
and retainer.

h.
Install
pump lifter
link,
metering rod
arm,
upper
pump spring, and retainer.

I.
Install
metering rod jet.

Note:
No gasket is used with this jet.

j.
Install
diaphragm housing attaching screws in
the diaphragm housing, making sure that the

edges
of the diaphragm are not wrinkled.
Lower

into place and tighten screws evenly and securely,
k.
Install
throttle shaft seal, dust seal washer, and
shaft seal spring.

I.
Install
pump connector
link
in the throttle arm
assembly.
Install
throttle shaft arm assembly on
throttle shaft guiding connector
link
in pump lifter

link
hole.
CAUTION:
Linkage
must not bind in any throttle
position. If binding occurs,
loosen
clamp screw in
throttle arm, adjust slightly, then retighten screw.

m.
Install
pump check disc, disc retainer, and lock

ring.

n.
Install
metering rod and pin spring. Connect
metering rod spring.
o.
Check
and if necessary correct meter ing rod adjustment. Follow procedure of
Par.
E-16.
p.
Install
needle
seat and gasket assembly, needle,
float
and
float pin. The
stop
shoulder on the float
pin
must be on the side away from the bore of
the carburetor.

q.
Set float level to specifications. Follow pro­ cedure of
Par.
E-12.

r.
Install
air horn gasket and air horn assembly.

Install
attaching screws, lock washers, and choke
tube clamp assembly. Tighten center screws first,
s. Slide choke shaft and lever assembly into place
and
connect choke lever
spring.
Install
choke valve.
Center
the valve by tapping lightly, then hold in
place with fingers when tightening screws,
t.
Install
fast-idle connector rod with
offset
portion
of rod on top and pin spring on outside.
Install
fast-idle connecting rod spring.

E-23.
Correcting Acceleration
Flat
Spot

Early
production
Carburetor
Models 938-S, 938-
SA,
938-SC

Inasmuch
as a flat
spot
on acceleration or low speed
stumble can
come
from causes other than
car­

buretor
malfunction, it is recommended that
engine

tuning be thoroughly checked before attempting
any
actual carburetor work. Make sure that
ignition, compression, and timing are correct and
that fuel pump is supplying enough gas. Also, the F-head
engine
employs a water-heated intake

manifold.
Proper vaporization of the fuel depends
on correct intake manifold temperature. Since this
temperature is controlled by the cooling system
thermostat, include an operational check of the
thermostat when diagnosing the stumble. Operating
temperatures consistently below
155°F.
can cause stumble.

If
the stumble persists, a
YF-938-S,
YF-938-SA,

or
YF-938-SC
carburetor can be converted to a
YF-938-SD
carburetor by installing Special Kit
924161, consisting of a pump discharge check
needle, a metering rod, and a metering rod jet. If this kit is installed, the pump discharge check

needle
replaces the original
ball,
weight, and re­

tainer
and the small wire-type retainer used with
the
ball
check assembly must not be reinstalled.

When
installing the kit, check the size of the pump discharge jet, No. 2, Fig. E-14.
Early
production
YF-938S
and
YF-938SA
carburetors have a .025" [0,635 mm.] jet installed. If the carburetor being
converted has a .025" jet it must be opened up to .031" [0,787 mm.] by running a No. 68
drill
through
the jet as shown in
Fig.
E-14.
The jet must be drilled
as it is a pressed in part and cannot be replaced.
Upon
completing the installation of the conversion

kit,
mark
or tag the carburetor to indicate that it
is a
YF-938SD.
118

E

FUEL
SYSTEM
E-78. SERVICE DIHGNOSIS
Symptoms Probable Remedy

Excessive
Fuel
Consumption:
Tires
improperly inflated Inflate

Brakes
drag Adjust
Engine
operates too cold Check thermostat
Heat control valve inoperative Check thermostatic spring
Leak
in fuel line Check all connections

Carburetor
float level high. See
"Carburetor"
section
Accelerator pump not properly adjusted Adjust

Leaky
fuel pump diaphragm Replace
Loose
engine
mountings causing high carburetor fuel level Tighten Ignition timing slow or spark advance stuck See "Distributor" section

Low
compression. Check valve tappet clearance
Air
cleaner dirty
.
Remove and clean

Engine
Hesitates on Acceleration: Accelerator pump
does
not function perfectly.
...................
.Replace piston and rod or adjust
Carburetor
float level. ... .Adjust

Spark
plugs Replace or clean and adjust

Low
compression Check valves

Distributor
points—dirty or pitted Replace

Weak
condenser or coil Replace

Carburetor
jets restricted Remove and clean

Excessive
engine
heat See "Engine" section

Engine
Stalls—Won't Idle:
Improper
condition of carburetor See
"Carburetor"
section

Low
speed
jet restricted Remove and clean
Dirty
fuel sediment bowl screen Remove and clean

Air
cleaner dirty Remove and clean

Leaky
manifold or gasket Replace

Fuel
pump diaphragm porous. Replace
Loose carburetor. Tighten
flange
nuts

Water
in fuel
Drain
and clean system

Improper
ignition. .See "Distributor" section

Spark
plugs Clean and adjust

Valves
sticking.
Grind
valves 134