Onan MJB, MJC, RJC Service Manual

Service

Manual

Gasoline

Engine

967-0757

11-86

Printed

In

USA

Safety

Precautions

It is recommended that you read your engine manual and become thoroughly acquainted with your equipment before you start the engine. highly flammable.

DO

NOT

smoke

or

use an open flame

in

the vicinity of the

engine or fuel tank. Internal combustion engine fuels are

@

I-Thls

symbol

is

used

throughout

this

manual

to

warn

of

possible

serious

personal lnjuy.

1-1

This

symbol

refers

to

possible

equip-

ment

damage.

Fuels, electrical equipment. batteries, exhaust gases and mov-

ing

parts present potential hazards that could result in serious, personal injury. Take care in following these recommended procedures.

Safety

Codes

All

local, state and federal codes should be consulted ad

0

This engine is not designed

or

intended for use in aircraft.

complied with.

Any such use is at the owner’s sde risk

General

Provide appropriate fire extinguishers and install them in

convenient locations.

Use

an

extinguisher rated

ABC

by

NFPA.

0

Make sure that all fasteners on the engine are secure and accurately torqued. Keep guards in position over fans, driving belts, etc.

0

If

it is necessary to make adjustments while the engine is running, use extreme caution when dose to hot exhausts, moving parts, etc.

Protect Against Moving Parts

0

Do not wear loose clothing in the vicinity

of

moving parts,

such

as

PTO shafts, flywheels, blowers. couplings, fans,

belts,

etc.

0

Keep your hands away

from

moving parts.

Baltorles

0

Before starting work on the engine, disconnect batteries

to

prevent inadvertent starting of the engine.

DO

NOTSMOKE

while

servicing batteries. Lead acid bat-

teries give

off

a highly explosive hydrogen

gas

which

can

be

ignited by flame, electrical arcing or

by

smoking.

e

Verify

battery

polailty

before connecting battery cables.

Connect negative cable last.

Fuoi

Systm

0

DO

NOT

fill

fuel

tanks

while engine is running.

0

Fuel lines must be of steel piping, adequately secured, and free from leaks. Piping at the engine should

be

ap-

proved flexible line.

Do

not use copper piping for flexible lines as copper will work harden and become brittle enough to break.

Be sure all fuel supplies have a positive shutoff valve.

1

Exhaust System

0

Exhaust products

of

any internal combustion engine are

toxic and can cause injury,

or

death

if

inhaled.

All

engine applications, especially those within a confined area, should be equipped with an exhaust system

to

discharge

gases to the outside atmosphere.

DO

NOT use exhaust gases to heat a compartment.

0

Make sure that your exhaust system is free of leaks. Ensure that exhaust manifolds are secure and are not warped by bolts unevenly torqued.

Exhaust

Gas

Is

Deadly!

Exhaust gases contain carbon monoxide, a poisonous gas that might cause unconsciousness and death. It is an odorless and

colorless gas formed during combustion

of

hydrocarbon fuels.

Symptoms

of

carbon monoxide poisoning are:

Dizziness Vomiting Headache Muscular Twitching

If

you experience any of these symptoms, get out into fresh air

immediately, shutdown the unit

and

do not use until it has been

inspected. The best protection against carbon monoxide inhalation

is

proper installation

and

regular, frequent inspections

of

the

com-

plete exhaust system. If you notice a change in the sound orappearance

of

exhaust system, shut the unit down immediately

and have it inspected and repaired at

once

by a competent me-

chanic. Coaling

System

.

Weakness and Sleepiness Throbbing in Temples

*

Coolants under pressure have a higher boiling point than water.

DO

NOT

open a radiator pressure cap when cd-

ant temperature is above

21 2

degrees

F

(1

00

degrees C)

or

while engine is running.

Keep

The

Unit

And

Surrounding Area Clean

Make sure

that

oily ragsare not left on or near the engine.

0

Remove all unnecessary grease and oil from the unit. Accumulated grease and oil can cause overheating and subsequent engine damage and present a potential fire

hazard.

E4

Table

of

Contents

TITLE

PAGE

General Information

..................................................

2

Specifications

........................................................

3

Dimensions and Clearances

...........................................

4

Assembly Torques and Special Tools

..................................

6

Engine Troubleshooting

...............................................

7

Cooling System

.......................................................

8

Fuel System RJC

....................................................

19

Fuel System MJB-MJC

...............................................

31

Ignition System RJC

.................................................

41

Ignition System MJB-MJC

............................................

46

Oil System

..........................................................

54

Engine Disassembly

.................................................

64

Governor System

....................................................

39

Starting System

......................................................

57

INCORRECT SERVICE

OR

REPLACEMENT OF PARTS MIGHT RESULT IN

SEVERE PERSONAL INJURY AND/OR EQUIPMENT DAMAGE

.

SERVICE

PERSONNEL MUST

BE

QUALIFIED

TO

PERFORM ELECTRICAL AND/OR

MECHANICAL SERVICE

.

General Information

INTRODUCTION

This manual deals with specific mechanical and electrical

information needed by engine mechanics for troubleshooting, servicing, repairing, or overhauling

the

engine.

Use the table of contents for a quick reference to the separate engine sections.

Use the separate Parts Catalogs available at the dealer level, for parts identification and for establishing their proper location on assemblies.

The troubleshooting guide

is

provided as a quick refer-

ence for locating and correcting engine trouble. The illustrations and procedures presented

in

each section apply to the engines listed on the cover. The flywheel end

of

the engine is the front end

so

right and left sides

are determined by viewing the engine from the front. The disassembly section contains major overhaul pro-

cedures for step by step removal, disassembly, inspec-

tion, repair and assembly of the engine components.

If

a major repair or an overhaul is necessary, a competent mechanic should either do the job or supervise and check the work of the mechanic assigned to do the job to ensure that

all

dimensions, clearances and torque values

are within the specified tolerances. The wiring diagram on the last page of the manual shows

how the electrical components are interconnected.

A

parts catalog (available at the dealer level) contains

detailed exploded views

of

each assembly and the individual piece part numbers and their proper names for ordering replacement parts.

Use only Genuine Onan replacement parts to ensure quality and the best possible repair and overhaul results. When ordering parts, always use the complete Model and

Spec

number as well as the Serial number shown

on

the nameplate.

ENGINE MODEL REFERENCE

4

Identify your model by referring to the MODEL and SPEC (specification)

NO.

as shown on the unit nameplate.

Al-

ways use this number and the engine serial number when making reference to your engine.

,

How

to

Interpret MODEL

and

SPEC

NO.

12.5

RJC

18

R

/

96

AC

TT

12

34

56

1.

Kilowatt rating of unit.

2.

Factory code for series identification.

3.

18

-

Reconnectible for various voltages.

3C - Reconnectible for

120/240

volts.

4.

Specific Type:

E

-

ELECTRIC.

Electric starting at the set only.

R - REMOTE.

Electric starting. For permanent instal-

lation, can

be

connected to optional accessory equip-. ment for remote or automatic control of starting and stopping.

5.

Factory code for optional equipment.

6.

Specification (Spec) letter advances when factory makes production modifications.

2

Specifications

All

dimensions in

U.S.

customary units of measure (metric

in

parentheses) unless otherwise specified.

UNIT

OF

SERIES

SPECIFICATION MEASURE

MJB

MJC RJC

Number

of

Cylinders 2

4

Bore in

3.250 3.250 3.250

(mm)

(82.55) (82.55) (82.55)

Stroke in

3.625 3.625 3.625

(mm)

(92.07)

-

(92.07) (92.07)

(cm3) (983) (1 966) (1 966)

Compression Ratio 6.5 to

1

6.5

to

1

6.5 to

1

Displacement cu in

60

120 120

Firing Order 1-2-4-3 1-2-4-3 Oil Filter Full Flow Full Flow Full Flow Oil Capacity Without Qt

.

3 6

6

Oil

Capacity With Qt 3.5 6.5 6.5

Crankshaft Rotation

Governor Variable Speed Mechanical Valve Clearance (Cold)

Filter

(litre) (2.8)

(5.7) (5.7)

Filter Change

(litre) (3.3)

(6.2) (6.2)

(viewed from flywheel)

Clockwise

Clockwise Clockwise

Spec

A-C Begin

Spec

D

Intake in

0.01

0

0.014

0.01

5 0.015

(mm)

(0.25)

(0.36)

(0.38) (0.38)

Exhaust in

0.01

0

0.018

0.020 0.020

(mm)

(0.25)

(0.46)

(0.51) (0.51)

Spark Plug Gap in

0.025 0.035 0.035

(mm)

(0.64) (0.89) (0.89)

Breaker Point Gap

-

Static

(Full Separation and Engine Cold)

in

(0.020)

0.0150

0.0200

(mm) (0.51) (0.51) (0.38)O

(0.51)0

Ignition Timing (Static) 5"ATC

10'BTC

10"ATCO

9"

BTCO

Ignition Timing (Running)

25"

BTC 25" BTC

25'

BTCO

35" BTCO

Start Disconnect Point Gap

in

0.020

0.020 0.020

(mm) (0.51) (0.51) (0.51)

Distributor

Dwell

Angle

48'44'

48"

-54"

.

0

-

Magneto Ignition

0

-

Battery

Ignition

@

-Sasoline

Fuel

@

-

Gas

Fuel

3

Dimensions and Clearances

All clearances given at room temperature

of

70°F

(21°C)

.

All dimensions

in

inches (millimeters

in

parentheses) unless otherwise specified

.

CAMSHAFT

Bearing Journal Diameter. Front

.........................................

2.2500-2.2505 (57.150-57.1 63)

Bearing Journal Diameter. Center (MJC. RJC)

............................

1.2580-1.2582 (31.953-31.958)

Bearing Journal Diameter. Rear

..........................................

1.1875-1.1880 (30.163-30.175)

Bearing Clearance Limit (Original)

..............................................

.0015-. 0030 (.038-.076)

Bearing Clearance Limit (Replacement)

..........................................

.0012-.

0049 (.030-.123)

Cam Tappet Diameter (Prior

to

Spec P)

......................................

.7475-. 7480 (18.987-18.999)

Cam Tappet Hole Diameter (Prior

to

Spec

P)

.................................

.7507-. 7515 (19.068-19.088)

Cam Tappet Diameter (Begin Spec

P)

.......................................

.8725-. 8730 (22.162-22.174)

Cam Tappet Hole Diameter (Begin Spec

P)

..................................

.8755-. 8765 (22.238-22.263)

Large Bore Diameter

..................................................

2.1871-2.1876 (55.5523-55.5650)

Small Bore Diameter

......................................................

1.043-1.045 (26.4922-26.543)

(Center-to-Center)

..................................................

5.998-6.002 (152.3492-152.4508)

Connecting Rod End Play

............................................................

.002-. 016 (.05-.41)

End Play

............................................................................

.007-. 039 (0.2-1.0)

CONNECTING

RODS

Large Bearing Bore to Small Bearing Bore

CY

LlNDER

Bore Honed Diameter

......................................................

3.2495-3.2505 (82.537-82.563)

Maximum Allowable Taper

.................................................................

0.005

(0.127)

Maximum Allowable Out

of

Round

..........................................................

0.002 (0.051)

Main Bearing Journal Diameter (MJB)

.......................................

2.2437-2.2445 (56.99-57.01)

Main Bearing Journal Diameter (MJC. RJC)

...............................

2.2427-2.2435 (56.965-56.985)

Center Main Bearing Clearance (MJC. RJC)

.....................................

.0024-. 0052 (.061-.132)

Front and Rear Main Bearing Clearance (Original) (MJC. RJC)

....................

.0030-. 0043 (.076-,109)

Front and Rear Main Bearing Clearance (Replacement)

(MJC.

RJC)

.................

,0024-.0062 (.06-.16)

Main Bearing Clearance (Original) (MJB)

.........................................

.002-.

0033 (.051-.084)

Main Bearing Clearance (Replacement) (MJB)

.....................................

.0014-. 0052 (.04-.13)

Connecting Rod Journal Diameter

........................................

2.0597-2.0605 (52.316-52.337)

Rod Bearing Clearance

..........................................................

.001-. 0033 (.025-.084)

End Play

.........................................................................

,010-.015 (.254-.381)

Clearance in Cylinder Measure 90" to pin. just below oil ring

...........................................

.0012-. 0032 (.030-.081)

Ring Groove Width

CRANKSHAFT

PISTONS AND RINGS

TOP

.......................................................................

,0960-.0970 (2.438-2.464)

No-2

.....................................................................

.0955-.

0965( 2.426-2.451)

NO

.

3

......................................................................

,1880-.1895 (4.775-4.813)

Ring Gap

...........................................................................

.010-.

020 (.25-51)

Clearance

in

Piston

...................................................................

Thumb

Push

Fit

Connecting Rod Bushing Clearance

.............................................

.0002-. 0007 (.005-,018)

Rotation

...........................................................................

Counterclockwise

Pinion Clearance to Pinion Stop (Solenoid Plunger Bottomed)

.....

;

................

.070-.

120 (1.78-3.05)

Armature End Play

...............................................................

.005-.

030 (.030-,760)

PISTON PIN

STARTING

MOTOR

(Prestolite)

VALVE-INTAKE

Stem Diameter (Stem is tapered) **Center,,

.

,

.

. .

. , .

.

,

.

. .

.

,

. .

, ,

.

. , . .

. . .

. .

. . . .

. . .

. .

. . . .

. . . . .

. .

. . . . . .

.

,

. .

,

. .

.3401-.3411 (8.639-8.664)

**Face..

,

. . . . . . , . . . .

. . . . . . . . . . . . .

. .

.

. . .

. .

.

. .

. . . . . . . .

. . . . .

. . .

.

. . .

.

. .

.

. .

.

.3386-.3396 (8.601-8.626)

Valve Face..

.

. . . .

. . . . . . . . . . . .

. .

. . . . .

. .

. . . . .

. . . . . . .

. . . . .

. .

.

. . .

. . . . . . . . . . . . . . . . . .

.

. . .

.

, ,

45"

Guide Clearance

. .

. . . . . . .

.

. . . . .

. , . . . . . . . . . . . . .

. . . .

. . . . .

. . . .

. .

. . .

.

. .

.

. .

.

. .

.

.001-.003 (.025-.076)

Stem Diameter

.

. .

.

,

. .

. , .

. . .

. . . . . . . . . . .

. .

.

. .

. . . . . . . . . . .

. . . .

. . .

. .

. . . . . . . .

. . . .

.

-3405.3415 (8.649-8.674)

Guide Clearance

,

. . , .

.

. , .

. . . . . .

. . . . . . .

. .

. . .

.

. . .

. . . . . . . .

. . . . . . . . . .

.

. . . . . .

..

.

.0030-.0050

(.076-.127)

Valve Face..

. . .

. .

. . . . . . . . . . .

.

. .

. . , . .

.

. . .

. . . .

.

. .

. -.

. .

. . .

. .

. . . . . . . . . .

. . . . . . .

. . . . . .

. . . . .

.

. . . . .

. . .

.

45"

Length

...

..

.

.. ..

...

..

.

....

.. ..

. . . . . .

.....

. . . .

. ..

.

.. .

. . ..

..

. .

.

...

.

. .

.

...

.

...

..

.

1.7812 (45.2424)

Outside Diameter

. . , .

. . , . . .

. . , . . . . .

.

. . .

. . , . .

. .

. . . . . . . . . . . . .

.4690-.4695 (11.9126-11.9253)

Inside Diameter (after reaming)

Exhaust

.

. .

. . . . .

. . . . . . . . . . . .

. .

.

. .

. . . . .

.

. .

. . . .

. . . . . . . . .

.

. .

.

. . . . . . . . .

.3445-.3455 (8.750-8.776)

Intake

. . . .

. . .

. , . .

. .

. . . .

. . .

. . . . . .

.

. .

. . . . . . . . .

.

. .

.

. .

.

. .

. . . . . . .

. .

. . . .

. . . . . . .

.3425-.3435 (8.700-8.725)

Cylinder Block Bore Diameter..

. . . . . . . .

. . .

.

. . . . . .

. . . . .

. .

.

. . . .

.

. .

. . . . .

.

.467-.468 (11.8618-11.8872)

Valve Seat Bore (Diameter)

VALVE-EXHAUST

VALVE GUIDE

VALVE SEATS

Intake

.

. .

. . , . . . . . . .

. . . . . . .

. . . . .

. .

. . . . .

. . . . . . . . .

. . . .

.

. . . . .

. .

. . . . . . . . .

. . . .

1.547-1 548 (39.29-39.32)

Exhaust

. . . . . . .

. . . . . . . . . .

. .

.

. .

.

. . .

.

. .

. . . . . . . . .

. . . . . . . .

. .

. . . . . . . . . . . . . .

.

1.361-1.362 (34.570-34.595)

..

Depth (from Cylinder Head Face)

. . . . . .

. . .

. . . . .

.

. . . .

. . . . .

. . . .

. . .

.

.433-,439 (10.99-11.15)

Seat Outside Diameter

Exhaust

.

. . , .

. , . . . . . . .

. . .

.

. . . . . .

.

. . . . .

. . . . . . . . . . .

,

.

. . . . . . .

.

. . . .

.

1.364-1.365 (34.6456-34.6710)

Intake

. . . . . .

..

,

.

. . .

..

.

......

. .

..

. . . .. . . . . . . . . .

. . ...

. .

. . . .

.. ..

. . . . .

...

.. ..

.

1.550-1.551 (39.37-39.39)

Seat Width..

.

. .

. , .

. . . . . .

. . . . . . . . . . . . . . . .

. . . . .

. . . . . . . . . .

. .

.

. .

. . . . .

. .

.

. .

.

. .

. . . .

.

.047-.062 (1.19-1.57)

Angle.

,

. . . , . .

.

. .

.

. . . .

.

. .

. . . . .

. .

.

. . . . . . .

.

. . .

. .

.

. . . . . .

.

. . .

. .

. . . . .

. .

. . , . . . . . . . . .

.

-45"

Available Insert Oversizes..

.

. . . .

. . .

. .

. . . . . . .

. . . . .

. . . . . . . . . . . . . . . . . . . .

. .

. . .

.

. .

. . .

,

.

. . . . .

.

.002

(.0508)

.005

(.127) .010 (.254) .025 (.635)

Load-Valve Closed

. . .

. . . . . . .

. . .

. .

. . . . . . .

. .

. . . . . . . .

. .

. . .

.

. .

. . . . . . . . .

. .

. . . . . . . .

. .

45-49

Ib

(200-218

N*)

Load-Valve Open (Prior

to

Spec P)

.

. . . . . .

. .

.

. . . . .

. . . . . . .

. . . . . . . . . . . . . .

. . . . . .

.

83-93

Ib

(369-414

N*)

Load-Valve Open (Begin Spec

P).

. . . . .

.

. .

. . . . . . . . . . . . .

. . . . . . .

.

,

.

. . . .

. . . . . .

.

. .

.

87-97

Ib

(388-432

N*)

VALVE SPRINGS

*

N.

Base unit, Newtons. Unit

of

force.

**

Measure intake valve stem at points indicated.

Valve Stem Diameter

(Intake)

,-T-

FACE

.

2.96

in

5

Assembly

Torques

The assembly torques given here will assure proper tightness without danger of stripping threads

.

If a torque

wrench is not available. be careful not to strip threads

.

Use reasonable force only and a wrench of normal length

.

Specially designed place bolts do not require a lockwasher or gasket

.

Check all studs. nuts

and

screws often

and tighten as needed to keep them from working loose

.

Special

Tools

TORQUE SPECIFICATIONS (Ft

.

Lbs)

Center Main Bolt (4 cylinder)

..............

97-1 02

Connecting Rod Bolt

.....................

27-29

Cover-Rocker Box

.......................

8-10

Cylinder Head Bolt

......................

44-46

Exhaust Manifold Nuts

.................

13-1

5**

Flywheel Mounting Screws

................

65-70

Hub-to-Flywheel Screws

(4

cylinder)

.........

17-21

Fuel Pump Mounting Screws

...............

15-20

Gear Case Cover

.......................

18-20

Intake Manifold

.........................

13-1 5

Oil Base Mounting Screws

................

45-50

Oil Filter

.................

Hand Tight + 1/2 Turn

Oil Pump Mounting Screws

................

15-20

Rear Bearing Plate

......................

40-45

Rocker Arm Nut

........................

4-10*

Rocker Arm Stud

.......................

35-40

Spark Plug

............................

25-30

.

This

torque

is

from

friction between

the

threads only and

locks

the nuts in place

.

The

rocker arm nuts are

for

adjusting valve lash

.

**

-Tighten

nuts

evenly to avoid manifold damage.

.

These tools are available from

ONAN

to aid service and

repair work

.

Driver. Valve Seat

.......................

.42

0.0270

Oil Seal Guide and Driver

................

.42 0.0456

Valve Seat Remover

.....................

.42 0.0311

Replacement Blades for 420-0272

........

.42 0.0274

Crankshaft Gear Pulling Ring

............

.42 0.0248

Driver. Center Camshaft Bearing (4 Cyl.)

...

.42 0.0254

Driver. Combination Main and Cam

.......

.42 0.0326

Reamer. Ridge

..........................

.42 0.0260

Valve Guide Remover and Driver

.........

.42 0.0300

c

Troubleshooting

Guide

i

FUEL

SYSTEM

Cooling

System

PURPOSE

OF

COOLING SYSTEM

Purpose of the cooling system is to carry heat away from hot engine components to maintain proper running conditions and clearances. Overheating can severely damage engines. The cooling system must carry off excess heat.

Regulating coolant temperature helps keep the engine at optimal heat levels for each operating condition. After starting, engine must warm up quickly. During periods of peak output, it must be adequately cooled.

ANTI-FREEZE AND CORROSION

Corrosion can shorten engine life by plugging up radiator cores, building up around hot spots near the exhaust

valves, and settling in low areas of the block. The cor-

rosive sediment insulates against proper heat transfer

and holds heat

in.

Most of the metals used in cooling

systems are susceptible to corrosion damage that causes coolant leaks and temperature to rise above safe,

normal limits.

To

prevent corrosion, a mixture of anti-freeze and water

should always

be

used as an engine coolant, even when

freezing temperatures are not expected. Besides pre-

venting coolant freeze up, anti-freeze contains rust

in-

hibitors that prevent corrosion. Most anti-freeze

manufacturers recommend a minimum

50-50

mix of ethylene glycol anti-freeze and water for winter and summer in closed water systems, with a complete change every year to avoid corrosion and more expensive damage.

HIGH

TEMPERATURE CUT-OFF SWITCH

The high temperature cut-off switch shuts down engine if coolant reaches a dangerously high temperature.

This

normally

closed

switch senses coolant temperature in engine cooling jacket. When engine temperature rises beyond a specific point the switch opens, breaking the circuit to fuel solenoid. When coolant temperature falls

to

a

safe operating range the switch doses, permitting

engine restarting.

Stopping of engine due to action of high temperature

cutoff switch

is

not a

normal

condition. Examine coding

system

to

determine

the

cause

of

overheating,

and repair

as

required.

COOLING SYSTEM MAINTENANCE

The cooling system, including block and radiator, should be cleaned and flushed at least once a year. This is es-

pecially important in cold weather conditions or when preparing unit for extended storage (over

30

days or

more)! The cooling system can work efficiently only when

it

is

clean. Scale and rust in the cooling system slow down

heat absorption and restrict water flow.

The thermostat is calibrated to open at a specific temperature. It should be checked to be sure

it

is operating.

An appropriate anti-freeze mixture should

be

used in

colder climates as necessary. Check fan belt tension periodically. For proper operation

of water pump, fan belt should be tight enough to prevent slipping.

Check water pump for wear periodically. Loosen fan belt and move fan and water pump pulley back and forth. If wear is excessive, replace bearing.

Cleaning

and

Flushing Cooling

System

To clean

rust

and scale deposits from cooling system, drain system and then fill with clean water and cleaner solution. Use an approved chemical cleaner (such as type used

for cleaning automotive cooling systems) and follow

instructions provided by the supplier.

Liil

strong chemicals that can cause

burns

or other

injufy

if

used

improperly. Read all

w8rn-

ing

labels

carefully

before

using,

When cleaning is complete, drain cleaning solution and flush system. For best results engine and radiator, or heat exchanger, should

be

reverse flushed.

Allow

engine

to

cool

as much as possible before flushing with cold

water.

Never

pour

Cdd

water

into

a

hot

en-

g/m

Ddng

so

may crack

head

or cyi-

lnderblock.

Do

not

operate englne

w/thout

coolant for

won

a

few

minutes,

Flush

system

if

engine

operation

indicates clogged

pas-

sages

or

overheating.

Contact

WRh

hot

codant

might

/'08U/t

WARNING

Cleaning

SO/U~~O~S

typically contain

I

,

in

8WhS

burns.

b

not

bhd

hot,

pnrurrtird

cdanf

fm a ctoruf

codlng

sydm.

Engine Water

Jacket

and

Cylinder Head

External coolant leakage may occur at any joint

in

the

engine

water jacket, such as

drain

plugs, core hole plugs, or cylinder head joint. Since expansion or contraction can aggravate leakage, the block should be inspected both hot and cold while engine is running.

Internal leakage occurs when coolant passes into engine oil through a loose cylinder head joint or a cracked or porous casting. The leakage is not visible but may cause extensive damage to engine. Coolant mixes with the oil to form sludge, which causes lubrication failure. Heavy

sludge accumulations followed by sticking piston rings, valves, and tappets are symptoms of internal leakage.

Sometimes internal leaks are small enough to prevent coolant leakage but can permit exhaust gases to enter cooling system. The exhaust gases dissolve in the coolant, depleting rust inhibitors and forming acid which causes corrosion.

Thermostat

Replace thermostat if

it

is broken, corroded, or sticks in

open or closed position.

If

engine overheats or does not reach and maintain a minimum operating temperature, thermostat should be removed and tested as a possible cause.

1.

Remove thermostat from cylinder head.

2. Heat a pan of water to approximately

150°F.

Check

temperature, using a thermometer immersed in water.

3.

With thermostat suspended in water at temperature

of

15OoF,

thermostat should start to open.

4.

After thermostat has opened completely, remove

it

from hot water and allow

it

to cool in surrounding air.

The thermostat should close within a short time.

5.

If

thermostat sticks or does not operate properly, re-

6.

Always install a new gasket when replacing

place it with a new one.

thermostat.

Draining Cooling

System

Whenever draining cooling system to change anti-freeze solution or for out-of-service protection when only water is used,

be

sure to open all drains and hose connections

where water could

be

trapped.

The following drain plugs must be opened

or

removed

to allow complete flushing of the cooling system.

Radiator:

One petcock lower right front corner.

Engine

Block

One drain plug left front near water pump.

1

Water

Pumps:

One drain plug under cover or by

loos-

ening cover.

If

an optional water jacket tank heater is used it

should

be drained

and flushed

also.

The lower hose

must

be disconnected at tank

heater. There

is

no

drain

plug.

Contact with hot coolant might result

cizil

in serious burns.

Do

not bleed hot,

pressurized

coolant

from

a

closed

cooling

system.

After making repairs on cooling system, tighten all connections thoroughly. Use Permatex or thread sealing compound on all threaded connections

to

prevent leaks

or entry of air into system.

Read instructions

on

Permatex Sealer can before applying sealer

to

engine parts.

WARNlNG

Pressure Cap

The pressure cap increases boiling point of coolant by

allowing pressure40 build up in cooling system. The in-

crease in boiling point reduces the chances for coolant

loss

due to boil over. A

15

psi (1 03.5 kPa) pressure cap

will raise boiling point of water to

250°F

(122°C) and boiling point of a 50/50 mixture of water and anti-freeze to

265°F

(132°C). Pressure caps should be inspected periodically for freedom of operation, and gasket should be checked for proper sealing. Replace pressure cap if it malfunctions.

9

RADIATOR

COOLING

SYSTEM

On radiator cooled models (Figure

l),

the water pump draws cooled water from radiator through the bottom hose and forces it into cylinder water jacket at the front

of

engine. Water circulates through the cylinder water jacket up through cylinder heads to thermostat and flows through the outlet hose into top of radiator.

It

circulates down through radiator while the fan blows cooling air across radiator. Water is drawn from the bottom of radiator by the pump to be recirculated.

THERMOSTAT

/

HIGH TEMPERATURE

INLET HOSE

1

lLLEiD-/:-':-:

WATER FLOW, ENGINE COOLING

-

AIR FLOW, ENGINE VENTILATION

FIGURE

1.

RADIATOR

COOLING

SYSTEM

During engine warmup, when thermostat

is

closed, water

bypasses radiator.

It

flows through a bypass line from the water outlet housing to pump and recirculates through the engine. When water in engine block reaches normal operating temperature, thermostat opens. This permits heated water to flow into radiator to

be

cooled.

Recirculation ensures both rapid and even temperature increase of

all

engine parts during warmup.

Ventilation for radiator

cooled

models requires an inlet opening for fresh air and an outlet opening for heated air to prevent recirculation of heated air. The openings

should

be

at least the size of radiator.

An expansion area in

the

closed cool-

Ez3

ing system maintains

proper

coolant

level

by

preventhg

overflow

and

loss

of

coolant

when

englne

heats

up.

CAUT,ON

Water

Pump

A

centrifugal

type

water pump (Figure

2)

circulates

cool-

ant

through

coding

system.

The

water

pump is secured

to cylinder

block

with

capscrews and is

belt

driven

from

the

crankshaft pulley. Coolant is drawn through pump

inlet opening

by

impeller and forced through outlet

open-

ing in backside of pump into cylinder

block.

A

gasket on

water pump outlet assures a leakproof connection.

PULLEY

BY-PASS LINE

HOUSING GASKET

FIGURE

2.

WATER

PUMP-EXPLODED

VIEW

Water pump is constructed to provide long life with a

'minimum amount

of

attention when proper corrosion preventive coolant is used. Care must be taken to keep grit and abrasive material from being circulated through cooling system. Water containing scale-forming materials is especially harmful to pump parts.

Pump cannot be rebuilt and

must

be replaced as a unit.

Check condition of bearing and shaft assembly by turning

water pump pulley. If bearing feels rough or binds, seal

is leaking,

or

housing is cracked, the pump must be

replaced.

Removal and Installation:

1.

Drain cooling system at radiator and engine block.

WARNING

Contact

with

hot

coolant might result

-

in serious burns. Allow cooling

sys-

tem

to

cool

before

releasing pressure and loosening

lines.

2.

Remove housing from radiator

as

necessary.

3.

Disconnect both hoses from radiator.

4.

Remove radiator.

5.

Loosen fan belt.

6.

Remove fan and water pump pulley.

7. Disconnect bypass line and radiator lower hose from

8.

Remove water pump from water pump housing.

9.

Installation is the reverse of removal.

Pump.

'PL

.

CITY WATER COOLED

On city water cooled models (Figure

3)

the lockshield

valve

is

manually

adjusted with

a

key

to

provide the

re-

quired minimum rate of water flow for cooling. Whenever ignition is turned on, the solenoid valve opens pressur-

ized

water inlet line.

During operation, water from pressurized source flows through lockshield valve and solenoid valve and through inlet line and enters at the bottom of cylinder water jacket at two places, one entry for each pair of cylinders. Water circulates around and up cylinder jacket through cylinder heads where it leaves engine through a thermostat and cover at each of the

two

cylinder heads. From the ther-

mostat covers, water passes through exhaust manifold

and is drained from engine cooling system.

During engine warmup, when the thermostats are closed, a water by-pass line controls the amount of water through cylinder water jacket until thermostats open. The by-pass line also continues to function during operation because it contains the high water temperature cut-off switch and water temperature sender unit.

Ventilation for these models is necessary for sufficient fresh air movement to cool generator and support com-

bustion for the engine.

HIGH WATER

TEMPERATURE

CUT-OFF

SWITCH7

Check thermostat opening and closing with thermostat immersed in a water bath. Thermostat should start to open when water temperature reaches 145°F and should

be

fully

open

at

165°F.

Take

thermostat

out

of

water

and

it should close in approximately

60

seconds.

If

it does

not operate properly, replace

it.

HEAT EXCHANGER

COOLING

(OPTIONAL)

ONAN

heat exchanger cooling

is

available either factory

installed or as a kit for customer installation.

A

complete

heat exchanger installation (Figure 4) contains

two

in-

dependent water systems:

1.

a closed water system

2.

an open (raw) water system

In the closed water system, a centrifugal pump draws

water from an expansion tank and pumps

it

through cooling tubes in a heat exchanger and into the engine water jacket where

it

circulates out through a thermostat back into expansion tank for recirculation. In the open water system, pressurized water is forced around the cooling

tubes through heat exchanger and through exhaust man-

ifold where it is discharged.

WATER

TEMPERATURE

@

SENDER UNIT

T

LEGEND

-+

WATER

INLET

-ma--*

CIRCULATION

1:.

/&p

WATER INLETLINE

SOLENOID VALVE

/

,LOCK SHIELD KEY

LOCK SHIELD VALVE

--

WATER

OUTLET

FtQURE

9.

CITY

WATER

Coouffi

SYSTEM

FIGURE

4.

HEAT EXCHANGER COOLING

SYSTEM

Maintenance of closed water system is the same as radiator cooled system. Clean and flush

it

once a year and

use anti-freeze

if

there is danger

of

freezing. Use a rust

inhibitor in the expansion tank (closed water system).

In an open water system, check periodically for air leaks, wear or damage, or restricted lines.

Open water portion of heat exchanger

is

protected from corrosion by a zinc pencil mounted on a pipe plug in one end

of

the heat exchanger. Inspect the pencil at least

every

two

months and replace if deteriorated

to

less than

one half original size (Figure

5).

ZINC

PENCIL

,UWWATCUIN

AC"C':NW.TER

Clean and flush cooling system

if

conditions warrant.

To clean closed water system, drain and refill with radiator cleaner. When chemical cleaning is completed, according to the cleaner manufacturers instructions, flush cooling system to wash out deposits loosened by chemical cleaning action.

Flush the engine water jacket. Hose from engine water jacket to heat exchanger should

be

removed for water outlet. Flush both closed water portion and raw water portion of heat exchanger. Remove lockshield valve and solenoid valve to flush raw water portion.

Also

flush

water

cooled

exhaust manifold. When flushing

is

completed, check system thoroughly for any leaks uncovered by cleaning operation.

Repair and test raw water system for air leaks and

in-

sufficient water flow.

Heat exchanger repair, if

it

should become clogged, con-

sists of removing the ends and cleaning the tubes.

FIGURE

5.

HEAT

EXCHANGER

AND

ZINC

PENCIL

Water

Pump

(Centrifugal)

Pump repair is necessary if pump is leaking or bearings are worn. Disassemble pump and replace worn components (Figure

6).

1.

Remove water inlet fitting, drive belt pulley, cover screws, and pump cover gasket.

2.

Unscrew threaded impeller from pump shaft by turning impeller in a counterclockwise direction when facing impeller.

3.

Slide seal seat, wear face, and bellows assembly

off

the shaft. Loosen clamp screw and slide pump body off the pedestal.

4.

Remove bearing lock ring and drive, shaft and bearing assembly out of the pedestal. Bearing is press fit on the shaft and comes

off

in one integral part. The bear-

ing

is

packed with a lifelong lubricant and is sealed at

each end.

Replace all worn components such as bearings, seals, wear face, and impeller, and use a new cover gasket. Assembly sequence is the reverse of the disassembly procedure.

FIGURE

7.

WATER

PUMP

CLEARANCES

After pump has been assembled (see Figure

7),

the impeller (B) must be centered in body cover space (C-C). Adjustment is made by moving pump body fore and aft until shaft can

be

rotated freely by hand without binding.

Pump must be adjusted with the drive belt

off.

If not centered properly, impeller will rub on the body or cover and quickly overheat. Clearance

(A-A)

may vary from

zero to

1/16

inch

(1.6

mm). Tighten lock screw when

adjustment

is

correct being careful not to alter the

setting. When pump is installed on the engine, check

to

see that pump pulley is aligned with crankshaft pulley and adjust as required.

LOCK

I

NG

BOLT DRAIN IMPELLER COVER

SCREW

PLUG

I

--I

CUCJ

I

nL

SEAT

=AET

COVER

FIGURE

6.

WATER

PUMP

ASSEMBLY

MARINE COOLED SYSTEM Maintenance

The cooling system on MJB and MJC engines is a liquid

coolant, pressure circulating, open system that uses raw water coolant (sea water).

Factory

installed

heat

exchangers for a closed system

are

available

as an optional

feature

and

are discussed separately.

In a raw water cooling system (Figure

8),

water enters

pump located on the front left side of engine. The pump

delivers water

to

bottom of cylinder jacket and

it

flows

up the jacket and out an opening in cylinder head, which

is controlled by the thermostat. For engine warm-up,

when thermostat is closed, a by-pass from the cylinder

block entrance to thermostat cover allows water flow. In addition, a notch in thermostat allows some water flow through cylinder jacket and heads. From thermostat, water passes through water cooled exhaust manifold and

out of engine cooling system.

HE

Cooling system maintenance should include periodic inspection for leaks, inspection of the rubber pump im-

peller, and periodic flushing and cleaning.

-

in serious burns. Do not bleed hot,

pressurized coolant

from

a

closed cooling system.

The rubber impeller, because of continuous flexing, deteriorates with time and must eventually be replaced. If, however, the impeller fails after short service (usually under

500

hours) check for possible defects.

Only a clean cooling system can operate efficiently. Scale slows down heat absorption and restricts water flow. Flush system at least once a year and more often if operation indicates clogged passages or over-heating. To flush engine, remove thermostat, Figure

10,

and water

pump cover. Restrict the pump opening partially

so

cylinder block fills with water. Attach flushing gun nozzle to thermostat opening and fill block with water, then apply air pressure. Repeat process until water coming from block

is

clean.

WARNING

Contact

with

hot coolant might result

WATER

COOLED

EXHAUST

MANIFOLD

FIGWE

8.

CoOuNa

SYSTEM

Testing

The cooling system can

be

tested for 2 abnormal con-

ditions:

(1)

insufficient water flow and

(2)

air

leaks.

1.

To

measure water flow, install a tank of known quan-

tity

at the water outlet. Run engine until thermostat opens and then measure the length of time necessary to

fill

the tank. From this obtain the flow in gallons per

minute

(GPM).

If

water flow

is

below minimum, check pump operation and inspect passages and water lines for clogging.

2. Air

leaks are an important cause

of

premature impeller

failure.

To

test for air in cooling system, run engine,

insert cooling system outlet into

a

tank of water, and watch for bubbles. If bubbles appear, inspect cooling system thoroughly to find the source.

Repair

Whenever making repairs

on

cooling system, tighten all connections thoroughly. Use thread sealing compound on all threaded connections. This is especially important because of the damage air can cause.

PLUG

EXHAUST

MANIFOLD

i

DRAIN

BLOCK

HERE

(SOME

MODELS

HAVE

A

PIPE

PLUG)

REMOVE

PUMP

COVER

TO

DRAIN

All

water lines should be

1/2

inch inside diameter or larger. Long runs of pipe or hose need larger inside diameters to reduce resistance. Remember, the final test

is always correct water flow.

Thermostat

A

thermostat

is

located

on

right side

of

each cylinder head, connected by tubing to water cooled manifold. Replace thermostat if damaged by corrosion or other causes.

Check thermostat opening and closing with

a

thermometer in a water bath. Thermostat should start to open when water temperature reaches

145°F

and be

fully

open at 165°F. Lift it out of the water and

it

should close

in a short time. Replace thermostat

if

it

doesn’t operate

properly.

Water

Pump

The positive-displacement, rubber-impeller water pump

is located on the upper

left

corner of the gear cover.

Most water pump failures are caused by rubber impeller

failure. If impeller fails, check for pock marks on its end

surfaces. This is a sign of air in cooling system, which reduces pump lubrication and causes overheating.

If

pump leaks water along its shaft, replace water seals (early models) or seal assembly (late models). If cam, wear plate, or end cover show excessive wear, replace it.

Disassembly (Early Models):

1.

Loosen pump end plate screws and remove end plate.

COVER

THERMOSTAT

-

FIQUREQ.

COoilNG

SYSTEM

DRAINS

FlQURE

10.

THERMOSTAT

15

x~~STALLTHIS

SEAL

WITH

LIP

/BODY

T

Oh

A

R

D

I

MPE

L

L E R-,

INSTP

AWAY

€1

MO

2.

3.

4.

5.

~LLTHIS

SEAL

WITHLIP

.E

R

'T

a.

SHAFT ASSEM0LY

SNAP

RING

WEAR

PLATE

BEARING

AND

SHAF

GASKE1,COVER

FIGURE

11.

WATER

PUMPS

Pull impeller and shaft out with a pair of pliers.

If

further disassembly

is

necessary, remove

pump

from engine by removing the two capscrews on its mounting base.

Loosen set screw on side of pump by three or four

turns, and tap

it

lightly to free cam from the pump

body. Lift out cam and wear plate. Drive the

two

water seals out from the drive end

of

the pump.

Romove

only

if

they

are

to

be

replaced.

Disassembly

(Late

Models):

1.

Loosen pump end plate screws and remove end plate.

2.

Pull impeller out with a pair of pliers or by prying with screwdrivers (avoid damage to body).

3.

If

further disassembly is necessary, remove pump

from engine by removing

the

two

capscrews

on

its

mounting base.

4.

Loosen

set

screw

on

side of pump by three or four

turns,

and

tap

it

lightly to

free

cam

from

pump

body.

Lift

out

cam

and

wear plate.

5.

Remove

seal

assembly by prying through drain slots.

(Install with faces clean and oiled.)

LATE

MODELS

6.

To

remove bearing and shaft assembly, drive out by striking impeller end of shaft using a brass or wood dowel to avoid damage.

Remove

only

if

0-Ring

or

bearing

is

to

be

replaced.

Assembly: Before beginning assembly, clean

all

old sealer from inside surfaces of pump body, cam and wear plate.

Early Models. Use suitable sealer on top surface and back face of cam as well as screw threads. Line up hole in cam with

tang

on wear plate.

Late Models. Use suitable sealer on screw threads only. Line up hole in wear plate with tang on the

cam.

Assembly instructions are reverse of disassembly instructions.

HEAT EXCHANGER COOLING (OPTIONAL)

ONAN

Marine Heat Exchanger cooling is available either

factory installed or as a

kit

for customer installation.

A

completed heat exchanger installation contains two

water

systems,

the

dosed

water

system

and

raw

water

system

(Figure

12).

The

closed

water system continu-

ously

recirculates

water

through

engine

water jacket, ex-

pansion tank, exhaust manifold, centrifugal pump, and

one

side of heat exchanger.

The

raw

water

system

uses

an engine-mounted, rubber-impeller pump to draw sea

or

dty

water

and

circulate

it

through

heat

exchanger,

before discharging

it.

COOLING

SYSTEM

CAPACITIES

OF

UNITS

EQUIPPED

WITH

ONAN

HEAT EXCHANGERS

M

JB

4.5

qts.

MJC

9.5

qts.

When planning

to

install any brand

of

heat exchanger other than

ONAN

ap

proved, or any keel cooler, consult the factory or an

ONAN

distributor.

To

insure an adequate installation,

fhe engine cooling system must

be

modified.

Maintenance

Maintain closed water system the same as an automatic

radiator cooling system. Clean and flush

it

once a year and use an anti-freeze if there is danger of freezing. Use of a rust inhibitor in the expansion tank (closed water system) is recommended.

In sea water system, check periodically for air leaks, rubber impeller wear or damage, and restricted lines.

Raw water

side

of heat exchanger

is

protected from corrosion by a zinc pencil mounted on a pipe plug in one end of heat exchanger. Inspect pencil at least every

2

months and

replace

if

deteriorated to

less

than

1

/2

orig-

inal

size, Figure

13.

Cleaning

Clean and

flush

cooling system at least

once

a

year and

more often if conditions warrant.

To

clean closed water system, drain and refill with radiator cleaner. When chemical cleaning is completed, according to cleaner manu-

facturer’s instructions,

flush

the cooling system to wash

out loosened deposits.

Flush engine water jacket as discussed

in

Maintenance Section, except that the hose from engine water jacket to heat exchanger should

be

removed from water outlet. Flush both closed water side and raw water side of heat exchanger. Remove rubber impeller pump cover to flush raw water side.

Also

flush water cooled exhaust mani-

fold. When flushing

is

completed, check system thor-

oughly for leaks uncovered by cleaning operations.

EARLY

MODELS

CENTRIFUGAL

‘~NGINELUIYEN

WATER

PUU?

4

LATE

MODELS

RAW

COOLING WATER

FROU

SOURCE

RQURE

12.

HEAT

EXCHANaER

COOLING

Heat

Exchanger

Repair

The heat exchanger should never require any repair under normal service conditions. However, if

it

should be-

come clogged, remove ends and clean out tubes.

CENTRIFUGAL PUMP REPAIR

The cenrrirugal fresh water pump is mounted on the heat exchanger bracket.

If

it

should leak, or if bearings should

require replacement, disassemble

it

and replace the worn

components (Figure

6).

THERMOSTATS AND EXPANSION TANK

On MJB engines, the expansion tank serves as the thermostat housing. On MJC engines,

it

houses the ther-

mostat for the front two cylinders.

To

remove expansion tank, remove two capscrews extending down through the tank. When installing tank, be sure all connections are tight.

Check the expansion tank

fill

cap. This is a pressurized

cap, designed to hold

12-1

5

psi. Correct cap, good gaskets, and smooth gasket surfaces are essential for preventing

loss

of coolant.

I

7/16"

tI

+I

2

CYLINDER MODELS

4

CYLINDER MODELS

ACTUAL SIZE -REPLACE WHEN DETERIORATED

TO

ONE HALF

OF

ORIGINAL SIZE.

FIGURE

13.

ZINC

PENCIL

18

Fuel

System

RJC

Standard

RJG

engines use a gasoline-carbureted fuel

system to deliver

a

mixture of fuel and air to combustion chamber. The system draws fuel from a tank, delivers it through a filter and fuel pump (Figure

14),

to

the carburetor float chamber. Air passing through the carburetor venturi draws fuel from the float chamber.

A

combination gasoline-gaseous fuel carburetor or

straight gaseous fuel carburetors are available

for

use

RMO-MAGNETIC

IMING LEVER

FUEL

FILTER

FIGURE

14.

GASOLINE FUEL

SYSTEM

CARBURETOR

TERM.

I

,REGULATOR

with gaseous fuels. A gaseous fuel system uses a fuel

regulator (Figure

15)

to control the flow

of

gas from lines

to

carburetor. At carburetor, the gaseous fuel is mixed

with incoming air.

All

fuel system components are described in the following

paragraphs. Select the components that apply to your

engine.

FUELS

Ignition of fuel might cause serious

czil

personal

injury

or

death by

fire

or

ex-

plosion.

Do

not

permit any flame, cigarette,

or

other

igniter near

the

fuel

system.

Onan recommends the use of clean, fresh, unleaded gasoline. Regular leaded gasoline may be used.

Do

not use highly leaded premium fuels. Using unleaded gasoline results in less maintenance.

WARNING

If

regular gasoline is used continually, carbon and lead deposits must be removed from cylinder heads as required because of engine power

loss.

Unleaded gasoline

may

be

used safely after lead deposits have been

removed.

Failure

to

remove lead deposits prior

to

use of unleaded fuel can cause

pre-ignnion and possible engine damage.

MAINTENANCE

On gasoline fuel systems, periodic maintenance consists

of

cleaning fuel strainer, cleaning or replacing air cleaner,

carburetor adjustment

and

complete cleaning.

,CARBURETOR

NEW SYSTEM

CAS

,

REGULATOR

PIPE

'

TO

CONTROL

A

I

SUPPORTI

f

TERM.4

'

1.1

p-

DRY

FUEL FILTER

HoET,PIPE SUPPORT

r

TO

CONTROL TERM.

I

,-TO

CONTROL TERM. 4

I

-Ja*-T

-

%

VENT

%J

~

MANUAL

S~UTSFF~

HOSE

uw

GAS

SOLENOID VALVE

GAS

SOLENOID VALVE

RQURE

15.

aAsEOUS

FUEL

CARBURETION

SYSTEMS

19

FUEL

FIL1

FIGURE

16.

FUEL STRAINER CLEANING

To

clean fuel strainer, remove fuel sediment bowl and

screen (Figure

16)

and thoroughly wash the screen.

At

the same time, remove and clean carburetor float bowl. Assemble. and check for leaks.

On gaseous fuel systems, periodic service should include cleaning

or

replacing air cleaner, carburetor adjustment, inspection of hoses, etc. and cleaning optional dry fuel filter.

FUEL PUMP (GASOLINE FUEL

SYSTEM)

The fuel pump (Figure

18)

is located on left side of engine.

If

fuel does not reach carburetor, make the following

checks:

1.

Check fuel tank and see that shut-off valve is open.

2.

Remove fuel line from pump outlet. Connect a fuel pump pressure gauge to pump outlet and crank engine over several times. On manual models, operate priming lever instead of cranking engine. Fuel pressure should

be

1-2

psi. If not, remove pump for repair or

replacement.

WARNING

JgnMm

of

frnl

mbht

C8UW

slour

a

pu8mal

/nlury

or

death

by

fire

or

ex-

/gnRer

near

the

fml

system.

@08kn.

vfi

8y

f/8lM,

Cuawe,

Of

Ofk

FIGURE

17.

TESTING FUEL PUMP PRESSURE

Testing

Perform these tests before removing pump from the en-

gine. If fuel pump delivers fuel, test

it

with a pressure

gauge or manometer.

1.

Disconnect pump outlet line and install pressure gauge (Figure

17).

2.

Test valves and diaphragm by operating priming lever a few times. The pressure should not drop off rapidly after priming has stopped.

3.

Run engine with adequate ventilation at governed speed on fuel remaining in carburetor, and measure fuel pump pressure developed. Pressure should be

between

2

and 3 psi with gauge held

16

inches above

fuel pump.

A

low pressure reading indicates extreme wear in one

part or some wear in all parts; overhaul or replace pump.

If reading

is

above maximum, diaphragm is probably too tight or diaphragm spring too strong. This can also be caused by fuel seeping under diaphragm retainer nut and

between diaphragm layers, causing

a

bulge in dia-

phragm. Overhaul pump and replace defective parts. Low pressure with

little

or

no

pressure leak after pumping stops indicates a weak or broken spring or worn linkage. In most cases pump should

be

replaced.

Removal and Disassembly

1.

Remove pump inlet and outlet (Figure

18).

Remove

two

capscrews holding pump to engine

and

lift

it

off.

2.

Notch pump cover and body with a file for assembly

in

same

relative

position,

and

remove

six

screws

hold-

ing

them

together.

3;

Tap

body

with a screwdriver to separate

two

parts.

Do

not pry them

apart;

this may damage diaphragm.

4.

Lift

out diaphragm assembly and diaphragm spring.

20

VALVE AND CAGE

ASSEMBLIES

FILTER

A

ELEMENT

‘I

PRIMARY

FILTER

BOWL

U

FIGURE

18.

FUEL PUMP

Repair

CHOKE

(GASOLINE

FUEL

SYSTEM)

Fuel pump failure is usually due to a leaking diaphragm, valve, or valve gasket.

A

kit is available for replacement of these parts. Because extent of wear cannot easily be detected, replace all parts in the kit. If diaphragm is broken or leaks, check for diluted crankcase

oil.

Occasionally, failure is due to a broken or weak spring, or to wear in the linkage. In this case, install a new pump.

Assembly

1.

Before installing new diaphragm, soak it in fuel. Insert

diaphragm spring and fuel-soaked diaphragm into

pump

body.

2.

Compress rocker spring and install between body and

rocker arm.

3. Assemble cover to

body

with notch marks lined up.

Install screws but don’t tighten. Push rocker arm in

a

full stroke and hold in this position to flex diaphragm.

WARNING

Fuel

/eakage

IS

a

fire

and

explosion

-

hazad that might

cause severe

per-

sonallnjury

or

death.

Use care

when reassembling

fuel

pump.

A//

parts

must

al/gn

perfectly

or

pump

wtll

leak

finl.

Rn

dlrphmgm

must

k

fhxd

or

it

wHI

drlhrwtw

much

finl

pmrun.

4.

Tighten

cover

screws

alternately

and

securely,

then

5.

Install pump

on

engine

and

repeat pressure

test.

release rocker

arm.

The choke

on

remote starting

RJC

engines, built prior

to

Spec

C,

is an automatic electric type (Figure

20).

An electric element controls the choke. When engine is started, the generator supplies current to heating element which heats a bi-metal choke coil.

As

this coil heats,

it

winds tighter, opening the choke.

Electric choke adjustment for normal operation is done

by measuring distance ‘(Figure

20)

between choke plate and carburetor throat with engine cold. Use straight shank end of a drill bit to measure gap. Air cleaner must be removed for choke adjustment.

To

adjust choke, loosen retaining screws on the end plate and rotate cover assembly.

Extreme temperature conditions may necessitate readjusting choke. Increase choke by turning cover clockwise; to decrease turn

it

counterclockwise.

Operation and Adjustment, Thermo-Magnetic

Choke

This choke uses a strip heating element and a heat-sen-

sitive bimetal spring to control choke position.

A

solenoid,

actuated during engine cranking, closes choke

all

or part

way, depending

on

ambient temperature.

The

bimetal

is

calibrated to position choke at the proper

opening under any ambient

condibion.

Choke

is

adjusted

at

the

factory.

If,

for

any reason, readjustment

is

re-

quired, use

the

following procedure.

Adjustment must

be

made with the bimetal at ambient

temperature.

Do

not attempt adjustments until engine has been shut down for at least one hour. Remove air cleaner to expose carburetor throat. Loosen screw which secures the choke body assembly. Refer to Figure

19 for correct choke setting according to temperature. Use a drill bit to measure the choke opening. Rotating the choke body clockwise richens mixture, and rotating

it

counterclockwise leans the choking effect. Tighten screw that secures choke body.

AMBIENT

TEMP.

(OF)

60

65

CHOKE

OPENING

(Inches)

118

9/64

Disassembly and Repair, Electric and ThermoMagnetic

Choke

If

choke does not operate, or will not maintain its ad-

justment, diassemble

it

for repair. If it will not close, check for binding, incorrect adjustment, or incorrect assembly of coil. If

it

will not open after engine starts, check for

heating. Choke should be warm to the touch within a

minute or two of engine starting. To disassemble choke,

refer to Figure

20.

70

75

80

85

90

95

100

5/32

11/64

3/16 13/64 7/32 15/64 1/4

Electric Choke

If choke will not heat properly, check for a broken heating

coil or high-resistance electrical connections. Check coil

resistance with ohmmeter. With element at room temperature, resistance should

be

about 5 to 6 ohms for

12

volt models, about

25

ohms for

24

volt models, and

about

16

ohms for

32

volt models.

If

coil

is defective,

replace thermostat cover.

AVERAGE

CHOKE

SETTINGS

AMBIENT

CHOKE

TO

TEMP.-F\

BOW

1/16

3/32

7/64

I

/8

96

9/64

IO0

I

1/64

ELECTRIC

THIS

WAY FOR

LEANER

MIXTURE

When assembling electric choke be sure slot in cover tab

straddles and holds outer end of coil spring and that the spring winds in a clockwise direction from center.

Therrno-Magnetic Choke (Begin Spec C)

If choke will not heat properly, check for broken heater

wire, high-resistance connections, or broken lead wires

to bimetal and heater assembly. With element at room temperature, check heater resistance with an ohmmeter. Resistance should be abodt

30.6

to

37.4

ohms for a

12

volt system. If heater is defective, replace

it

with a new

one.

When start button

is

engaged, the solenoid

should

cause spring-loaded armature to contact solenoid core. If this does not occur, check for broken lead wires or a

defective solenoid coil. There must be slack in lead wires between choke body and the bimetal and heater assembly. Solenoid coil resistance should be

2.09

to

2.31

ohms

in a

12

volt system.

When replacing cover on thermostat and heater assembly, be certain that choke heater lead wires have been correctly installed in choke housing. Improper replacement of lead wires can cause choke assembly to malfunction.

The wires enter choke assembly through a small notch that is cut in the edge of the housing.

A

cover holds wires in place and prevents movement when tightened. When properly installed, lead wires will hang freely under bimetal coil when choke is in either the open or closed position. The end of heater wire sleeve should

be

located

from

1/8

inch inside choke housing to flush with inside

wall.

I

'A

LOOSEN THESE

SCREWS AND ROTATE THE

ENTIRE COVER

ASSEMBLY

THERMO-MAGNETIC

LOOSEN THIS

SCREW AND

ROTATE THE

ASSEMBLY

GZ

-

ENTIRE COVER

HOKE OPENING

CHOKE

22

t

4

A876

ELECTRIC HEATING

INSERT INNER END

OF

COIL

IN

SLOT

IN

SHAFT

ELECTRIC CHOKE

--+

CATCH OUTER EN

OF

COIL IN SLOT

IN

COVER

TAB

WASHER

(17/64

I.D.

x

518

O.D.

x

1/16”)

r BODY

LIMIT LEVER

U

LATO K WASH E

K

r

CHOKE SPRING

/

Luvcn

-1-

~-

f

(f

HI

-

HI-

6

c--

RETAINING RING

BI-METAL

COIL

SOLENOID CORE

4

L

_e-

SOLENOID

COIL

--

ANDHEATER

ASSEMBLY

GROUND TERMINAL

SHAKEPROOF WASHER

GROUND LEAD

MOUNT1

3

NG

PLATE

WASHER

(14/64

I.D.

x

9/16

O.D.

x

1/16“

NUT

(5/16-18”)

A

FIGURE

20.

DISASSEMBLY

OF

ELECTRIC

AND

THERMO-ELECTRIC

CHOKE

When assembling thermomagnetic choke, bimetal and heater assembly is connected as

follows:

1.

Lead tagged G goes to ground terminal on coil

2.

Lead tagged H goes to either of the

H1

terminals on

CARBURETOR

BODY

FLOAT

solenoid.

solenoid core.

GASOLINE

CARBURETOR

The gasdine carburetor is a horizontal

draft

type.

It con-

sists

of

three major sections:

bowl

and

float,

idle circuit,

and load circuit. Fuel enters carburetor through the valve (Figure

21)

and

passes

into

float

chamber.

The

float

controls

fuel

level

in

bowl

by

dosing inlet valve when

fud

reaches a certain

height

and

opening

it

when fuel level drops.

ME

21.

CAlwREToR

INLETVALVE

23

.J

:

The idle circuit (Figure

22

and

23)

supplies fuel during

no-load operation and for small loads. Throttle is nearly

closed at no load, and intake manifold vacuum is high.

Pressure difference between manifold and float chamber causes fuel to flow through the idle circuit. The pressure difference draws fuel up through the hollow center of

main adjusting needle, through passages in carburetor

body to the idle

port.

Bleed holes in main adjusting needle allow air to mix with the fuel. When throttle is almost completely closed, fuel passes out through the idle port.

As

throttle is opened to increase power, fuel is also

drawn out through idle transfer

port

in the hollow main

adjusting needle. When load increases, engine governor opens the throttle

further.

As

carburetor air flow increases, this produces a low pressure at venturi (narrow section of carburetor throat). This pressure drop operates load circuit drawing fuel up main nozzle where it mixes with air at the nozzle opening. Main adjusting needle controls fuel delivery.

As

throttle opens, manifold vacuum decreases

so

idle circuit becomes less effective. In a certain range, the two circuits blend; both delivering fuel, but as load is increased, the load circuit takes over.

CHOKE

VALVE

IDLE JET OPERATING

MAIN

JET

OPERATING

RQURE

22.

CARBURETOR

CIRCUITS

BEGIN

SPEC

R

With load circuit -in operation, as load is increased, the throttle opens to deliver more fuel. Main nozzle will not immediately deliver this increased fuel, because of the

jets controlled by adjusting needle. To prevent lag when

load is increased,

a

metering well around the outside of the nozzle delivers fuel until main jet can catch up with increased demand.

Adjustment,

Electric

Choke

Under normal operation, adjust choke

so

distance meas-

ured between choke and carburetor throat (Figure

19)

is

as shown in table with the engine cold. Use the straight shank end of a drill bit to measure gap. The upturned air cleaner must be removed for choke adjustment. To

adjust choke, loosen the

two

screws on cover plate and

rotate cover assembly.

Forcing the needle against

its

seat

will

bend

the

needle. The needle

does

not shut

off

fuel completely when turned

all

the

way

in.

*NOTE: VENT EXTENDS THROUGH

ADA F'TE

R

ON

LATER MODELS

A

I

RXLEANE

R

IDLE \ET OPERATING

METERING

MAIN JET OPERATING

FIQURE

29.

CARBURETOR

CIRCUITS

PRIOR

TO

SPEC

R

24

'I

I

Adjustment, With Load Carburetor should

be

adjusted in 2 steps - first the idle

adjustment

and

then the load adjustment.

See

Figure

24.

If

the carburetor

Is

completely out

of

adjustment

50

the engine will

not run, open

both

needle valves 1 to

142

turns

off

their

seats

to

pennlt

starting.

Do

not

force

needle valves against their

seats.

This

wlll

damage

the

needle.

Adjustment, Without Load

1.

Start engine and allow

it

to warm

up.

Push in on gov-

ernor

mechanism to

slow

engine down

to

about

400

to

500

rpm.

2.

Set idle adjustment screw for even operation

(so

en-

gine is firing on all cylinders and running smoothly).

3.

Release governor mechanism to allow engine to accelerate. Engine should accelerate evenly and without a lag. If not, adjust needle outward about 112 turn and again slow down engine and release governor mechanism. Continue until engine accelerates evenly and without a lag after releasing governor.

With carburetor and governor adjusted, and engine running with no load (Figure

24),

allow 1132-inch clearance at stop pin to prevent excessive hunting when a large load is suddenly removed.

Before adjusting carburetor,

be

sure ignition system is working properly and governor is adjusted. Then allow engine to warm up.

1.

With no engine load, turn idle adjustment out until engine speed drops slightly below normal. Then turn needle in until speed returns to normal.

2.

Apply a full load to engine. Carefully turn main adjustment in until speed drops slightly below normal. Then turn needle out until speed returns to normal.

THROTTLE

MAIN FUEL

THIS DISTANCE

INCH AT NO LOAD

PRIOR

TO SPEC

R

Removal and Disassembly

1.

Remove fuel line, governor linkage, and electric choke

wire.

2.

Remove two carburetor mounting nuts and pull

off

carburetor.

3.

Remove air cleaner adapter and choke from

carburetor.

4.

Remove main fuel adjustment needle (begin Spec

R)

and float bowl nut and pull

off

bowl. Remove float pin

and float.

5.

Lift

out float valve and unscrew its seat.

DIS AT

iTANCE

NO LOAD

6.

Remove no-load adjusting needle, load adjusting

7.

Remove throttle plate screws and plate, and pull out

8.

Remove choke plate

screws

and plate and pull out

needle (prior to

Spec

R)

and spring.

throttle shaft.

choke shaft.

BEGIN SPEC

Cleaning and

Repair

Soak

all

components thoroughly in a carburetor cleaner,

following the cleaner manufacturer's instructions. Clean

all

carbon

from

carburetor bore, especially in area

of

the

throttle.

Blow

out

passages

with compressed

air.

If

pos-

sible, avoid using wire to clean out the passages.

CM

adjusting

needles

and

nozzle

for

damage. If

float

is

loaded

with

fuel

or

damaged, replace

it.

Float should

fit

freely

on

its

without

binding. Invert carburetor

body

and

measure

float

level (Figure

25).

MAIN FUEL

AD

JUSMENT

A

NYLON ROD EXTENDING DOWN THROUGH LOWER

SHROUD PAN

FKIURE

24.

ARwJ8WQ

aASOUNE

CARBURETOR

25

To check float level, remove entire main fuel adjustment assembly from float bowl. Unscrew large nut from the float bowl. Adjust float level by bending tab on the float as shown in Figure

25.

With full weight of float on the

spring, float-to-gasket gap should be

1

/16-inch.

Do

not

apply

excessive

pressure

to

float

valve.

To adjust float level, bend small tab that inlet valve rides on.

Check choke and throttle shafts for excessive side play, and replace

if

necessary.

Do

not remove teflon coating on throttle shaft. Coating reduces wear and friction between shaft and carburetor body.

'HIS

DIMENSION

SHOULD

BE

11/64

THIS

DIMENSION

SHOULD

BE

1/8"

(FROM

GASKET

TO

FLOAT)

HEAD OF PIN, WITH FULL WEIGHT

OF

FLOAT COMPRESSING

BOWLFLANGE

GASKET

INLET VALVE SPRING.

~913

Rev

FIGURE

w.

SETnNo

FLOAT

LEVEL

Assembly

and

Installation

1.

Install

throttle shaft and plate, using new screws.

Install with bevel mated to carburetor body.

On

plates marked

C,

install

with mark

on

side toward

To

center

plate,

back

off

stop

screw,

close

throttle

lever and

seat

plate

by

tapping

it

with

a

small

screw-

driver; then tighten

two

screws.

2.

Install

choke

shaft

and

plate.

Center

plate

in

same

manner

as

throttle

plate

(Step 1). Always

use

new

screws.

idle

port

when

viewed

from

flange

end

of

CarblJretor.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

Install main nozzle (prior to Spec

R),

making sure

it

seats in body casting. Install fuel inlet valve seat and valve.

Install float and float pin. Center pin

so

float bowl

does not ride against it. Check float level with carburetor casting inverted.

Set carburetor float 11/64-inch between free end of float and carburetor body. See Figure

25.

Install

bowl

ring gasket, bowl and bowl nut (and main

nozzle begin Spec

R).

Make sure that bowl

is

cen-

tered in gasket and tighten nut securely.

Install adjusting needle with its spring. Turn

in

until

main seats and back out 1 to 1-1/2 turns.

Install idle adjusting screw finger tight. Then back out 1 to 1-1/2 turns.

Reinstall choke and adjust. Install air horn assembly and gasket. Install carburetor on engine and connect gasoline

inlet, governor mechanism breather hose and choke. Install air cleaner.

GASEOUS FUEL CARBURETOR

The gaseous fuel carburetor (Figure

26)

is similar to the

gasoline carburetor in shape, but

it

differs in operation.

Gaseous carburetors contain

two

major sections, the idle

circuit and the load circuit.

Fuel

delivery depends on de-

mand created on fuel inlet line, Figure

27.

A

small vacuum on inlet line opens fuel regulator, delivering fuel. For noload operation, idle adjustment controls quantity of fuel allowed through the idle

port.

The throttle is almost

closed,

so

increased vacuum on engine side of carbure-

tor draws fuel through the idle passage. When

load

increases, the flow of air through carburetor draws fuel from main fuel port

located

at venturi of the carburetor.

Adjustment

Set carburetor idle adjustment and then the load

adjustment.

Ifm~b~outof~sothm~Wnot

nn,opm

#kadjummt

w

wtwOtum8;

thrn

mnk

wMk

oprnlno

mrh

diu-

untll

mpb

starts.

Adjust carburetor

in

the

same

manner

as

gasoline

car-

buretor.

Usually

idle adjustment will have

lii

effect

on operation, because of the hgh engine

speed.

26

.

Carburetorfloatand

needle

VaJW

choke

sparlc

plug

gap

-fuelwpply

Mhre

,

Replace

if

removed Remove

if

for

ex-

gas

-

reduces

for

gas

tendedoperetionan

WW

Removelockwire

Installlockwire

set

at

.025"

open

Cloae

Set

at

,025''

GAS

MAIN

r

ADJUSTMENT

'GAS

HOSE

TOREGULATOR

GAS MAIN

GAS IDLE ADJUSTMENT

ADJUSTMENT

-7

BEGIN SPEC

R

I

FIGURE

26.

GASEOUS FUEL CARBURETOR

Removal and Disassembly

1.

Remove fuel hose and governor linkage.

2.

Remove two carburetor mounting nuts and pull

off

3.

Remove float bowl (and main adjustment screw begin

4.

Remove throttle plate screws and plate and pull out

carburetor.

Spec

R),

Figure

27.

throttle shaft.

Repair and Assembly

Clean in a suitable carburetor cleaner and blow out idle passage. Check idle needle for wear or damage and main

adjustment for

worn

threads. For assembly, reverse the

disassembly procedure.

COMBINATION GAS-GASOLINE

CARBURETOR

This carburetor

operates

on

either gasdine

or

gaseous

fuels.

To

switch

operating

fuels,

make

adjustments a&

cording to Table

2.

The

combination carburetor consists

of

both

gasoline

and

gaseous fuel carburetors

on

a single

casting.

TTLE

I

PRIOR TO

I

,SPEC.

R

'TLE

BEGIN

SPEC.

R

~

..

/-

W

FIGURE

27.

GASEOUS FUEL ADJUSTMENTS

The combination gas-gasoline carburetor adjustment is the same as for gasoline.

See

Figure

28

for location of

adjustment needles.

TABLE

2.

FUEL CHANGE CONVERSIONS

I

~assupdvvaive

I

CIOM

I

om

I

27

7'

-,

."

GASOLINE IDLE ADJUSTMENT

-

GAS

IDLE

REGULATOR

PRIOR

TO

SPEC.

R

--

GAS

MAIN ADJUSTMENT

SPEC. BEGIN

R

FIGURE

28.

COMBINATION CARBURETOR ADJUSTMENTS

GASEOUS FUEL REGULATOR

Gas Regulator (Garretson)

The demand-type regulator opens upon a small vacuum from the carburetor. It supplies fuel on demand, and shuts

off

fuel flow when engine is stopped, or when there

is

no demand.

Regulator is simply a diaphragm with linkage connecting

it to a valve in the gas line.

A

small vacuum from engine

moves the diaphragm, opening delivery valve.

Testing

Blow into diaphragm vent hole on regulator cover; this should open the valve. An audible hiss indicates that the regulator is opening.

A

water manometer (Figure

29)

is the standard tool for testing regulator inlet pressure, which must be within the limits specified for your regulator. Use chart in Figure

29

to convert the difference in water level between the

two

tubes to pressure in ounces.

Gas

Regulator

(Algas)

The Algas regulator has no adjustments, and features a positive

lockoff

if

pressure

increases above

the

regulator

setting,

Maximum inlet pressure is 5 psi and minimum,

6

ounces.

Maximum allowable inlet pressure is

8

ounces; minimum

2

ounces.

If

gas line pressure is greater than 8 ounces, install a primary regulator to reduce the pressure. Regulator has an adjustment to control maximum pressure at which the regulator shuts off when there is no demand.

To

obtain maximum regulator sensitivity, adjust it to just shut off at your line pressure when there is no demand. Adjust regulator for shut

off

when there is no demand,

to prevent gas leaks. Factory adjusted shut-off is

be-

tween 2 and 4 ounces. If gas line pressure is between

4

and 8 ounces, readjust the screw (Figure

31).

To adjust regulator, gas line should

be

connected and the outlet hose removed. Make a warse adjustment by turning adjusting screw inward until hissing of escaping gas

at

outlet stops. Install a water manometer on inlet side of regulator to make the fine adjustment. With gas on, cover regulator outlet for a few seconds and then

open.

If regulator is leaking, the pressure shown on manometer will drop slightly or waver, indicating that the valve is opening. Turn screw inward slightly and repeat

test.

Continue until manometer holds steady as outlet

is

dosed

for a few seconds and then opened.

If

regulator does not deliver

fuel,

check

inlet pressure.

If

pressure

is

over 5 psi

(1

psi

with

optional solenoid valve)

a

primary

regulator

is required

to

reduce

inlet

pressure.

If

inlet

pressure is

within

the

required limits

and

regulator

will

not deliver

fuel

or

leaks, disassemble

it

for repair.

~h.

mmd

0”

ruppw~cl

rokndd

v~h~

X9079912,

kdtr

off

at

(I

01s

krkt

pmrun

of

rlloMlv

oyw

OM

pound.

An

optknrlv&*

k

MWbk

*

wm

nourn

30.

To disassemble regulator, carefully remove cover and separate

the

diaphragm

from

the

cover and

body.

A

kit

is available from

ONAN

to repair the regulator.

to

5

28

.ozl

INCHES

OF

WATER.

8

12

14

I

.73

3.46

5.2

6.9

8.7

10.4

13.8

17.3

21

24

28

*INDICATES EQUIVALENT

OF WATER LEVEL

DIF-

FERENCE

IN

OUNCES

REGULATOR

FIGURE

20.

WATER MANOMETER

\

HOSETO

CARBURETOR

GAS

FUEL

OUT

FIGURE

30. ALGAS

GAS REGULATOR

If this regulator appears defective, will not open or close,

or delivers insufficient fuel, check shut

off

pressure ad-

justment.

A

kit is available from

ONAN

to replace both

the diaphragm and valve.

Solenoid

Primer

(Algas

Regulator

Only)

Algas regulators

use

an optional solenoid primer to pro-

vide quick engine starting. The primer (Figure

32)

holds

regulator open during engine cranking.

It

can

be

adjusted

for a rich

or

lean

mixture

by

loosening

lock

nut

and

turn-

ing

the

primer

in

or

out. Turning primer clockwise richens

mixture.

*

To

adjust for proper priming

of

a cold engine, set primer

so

a hot engine (one with gas

in

regulator-carburetor

hose and caburetor) sounds slightly rough and produces

slightly

dark

exhaust when engine first

starts

firing.

GAS REGULATOR

FIGURE

31.

ADJUSTING

GAS

REGULATOR

E

A742

TO

STARTER

SIDE

OF

START

SOLENOID

TO GROUND

iOLENOlD

PRIMER

REGULATOR

*-

RQURE

92.

ALGAS

SOLENOID

PRIMER

29

'7

Initial Adjustment

1.

Remove regulator-carburetor hose at regulator and

2.

Turn primer clockwise (richer) until you can hear a

3.

Remove voltage, connect hose and attempt to start

If engine starts within 3 seconds, primer

is

correctly adjusted. If not, remove hose at regulator and crank engine for a few seconds to empty hose and carburetor of gas and readjust primer slightly. Connect hose and attempt to start. Continue until the engine starts within

3

seconds from an empty hose and carburetor. When primer is properly adjusted, be sure regulator locks

off

when unit

stops. To test primer, remove it from regulator, noting the num-

ber of turns necessary to unscrew

it

and operate the start switch. Plunger must extend out. If not, wiring or primer solenoid may be defective or plunger is stuck in

the primer body.

apply battery voltage across primer.

small flow of gas at outlet.

engine.

AIR

CLEANER

Two types of air cleaners are used; a dry paper type (folded paper), and a moistened foam

type

(synthetic

sponge),

Dry

Paper Type

(See

Figure

33.)

Remove and clean, either by shaking or

blowing out with compressed air at least every

100

hours.

Do

not wash it. When using cornpressed air, hold

nozzle far enough from cartridge

so

it will not rupture.

Replace cartridge at least every

500

hours.

If

paper cartridge has a foam wrapper, remove wrapper before cleaning, wash

it

in clean solvent, dry, and install on the

cartridge.

Foam

Type Cleaner

This cleaner consists of a foam element over a metal retainer (Figure

33).

About every

200

hours, remove

foam element and wash

it

thoroughly in a suitable

sol-

vent. Then dip it in clean crankcase grade oil and squeeze as dry

as

possible. The element should

be

replaced only

if

damaged.

EVERY 50

HOURS

OF OPERATION.

REPLACE AT LEAST

EVERY

500

HOURS

,+*y..'..K

.

:

?::.

+::;;

'

.'

EARLY

JB

DRY

PAPER-TYPE FILTER

AFTER WASHING ELEMENT IN

SOLVENT

DIP

IN ENGINE

01

L

AND

SQUEEZE

AS

DRY

AS

POSSIBLE

.

FOAM-TYPE

AIR

FILTER

FIGURE

33.

AIR

CLEANERS

30

Fuel

System

MJB-MJC

Standard MJB and MJC engines use a gasoline, carbureted, fuel system, to deliver a mixture

of

fuel and air to the combustion chamber. The fuel system draws fuel from a tank, delivers

it

through the filter and fuel pump

to the carburetor float chamber.

Air

passing through car-

buretor venturi section draws fuel from the float

chamber. All fuel system components are described in the following

paragraphs. Select the Components that apply to your engine.

FUELS

T-WA,N,NG

/snition

of

fuel might cause serious

-

personal injury or death

by

fire

or

ex-

plosion.

Do

not permit any flame, cigarette,

or

other

igniter near the fuel system.

Onan recommends the use

of

clean, fresh, unleaded gas-

oline. Regular leaded gasoline may be used.

Do

not use highly leaded premium fuels. Using unleaded gasoline results in less maintenance.

m

P

If regular gasoline is used continually, carbon and lead deposits must be removed from the cylinder heads, as required, because of engine power

loss.

Unleaded gasoline may be used safely after lead deposits have been removed.

Failure

to

remove lead deposits prior

rn

lo

use

of

unleaded fuel can cause

preignition and possible engine damage.

Maintenance

On gasoline fuel systems, periodic maintenance should consist of cteaning fuel strainer, cleaning or replacing air silencer or flame arrester, carburetor adjustment, and complete carburetor cleaning.

To

clean fuel strainer, remove fuel sediment bowl and

screen (Figure

35)

and wash the screen thoroughly. At the same time, remove carburetor float bowl and clean it. Assemble and check for leaks.

FUEL

PUMP

AND

FILTER

BODY

FtQURE

95.

SEDIMENT

WWL

WRE

34.

FUEL

SYSTEM

31

-.

c

FUEL PUMP

The fuel pump is located on left side of engine near the rear.

If

fuel does not reach carburetor, make the following

checks:

1.

Check fuel tank and see that shut-off valve is open.

2.

Remove fuel line from pump outlet. Connect a fuel pump pressure gauge to pump outlet and crank engine over several times. Fuel pressure should be

1-2

psi.

If

not, remove pump for repair or replacement.

Testing

If fuel pump delivers fuel, test

it

with a pressure gauge

or manometer. Perform these tests before removing

pump from engine. Disconnect pump outlet line and install pressure gauge (Figure 36).

Test valves and diaphragm by operating priming lever a few times and watching pressure. It should not drop

off

rapidly after priming has stopped.

Next, run engine at governed speed on fuel remaining in

carburetor and measure fuel pump pressure developed.

Pressure should

be

between 2 and 3-psi with gauge held

16 inches above fuel pump.

A

low

pressure reading indicates extreme wear in one

part or some wear in

all

parts, and pump should be over-

hauled or replaced. If reading is above maximum, dia-

phragm is probably too tight or diaphragm spring too strong. This can also be caused by fuel seeping under diaphragm retainer nut and between diaphragm layers, causing a bulge in diaphragm. Overhaul pump and replace defective parts.

Low pressure with little or no pressure leak after the

pumping stops indicates

a

weak or broken spring or a

worn linkage. In most cases pump should

be

replaced.

Fl

JEL

ou

Removal

and

Disassembly

1.

Remove pump inlet and outlet. Remove

the

2

cap-

screws

holding pump

to

the engine and

lift

it

off.

2.

Notch pump cover and body with a file

so

they can

be

assembled in same relative position, and remove

the

6 screws holding them together.

3. Tap body with a screwdriver to separate the

2

parts.

Do

not pry them apart - this would damage

diaphragm.

4.

Remove screws holding valve plate to cover and lift out valve and cage assemblies.

5.

Drive out rocker arm hinge pin.

6.

Remove rocker arm, spring and link.

7.

Ci

out diaphragm assembly and diaphragm spring.

Assembly

(Figure

37)

1.

When installing a new diaphragm, soak

it

in fuel before assembling. Insert diaphragm spring and fuel soaked diaphragm into pump body.

2.

Insert link and rocker arm into body and hook it over diaphragm pull rod. Align rocker arm with pin hole and drive in pin.

Fuel leakage

is

a fire and explosion

Lxl

hazard that might cause severe per-

sonal

injury

or

death.

Use

care when reassembling fuel

pump.

All parts

must

align perfectly

or

pump

will leak

fuel.

.

3.

Compress rocker spring and install between

body

and

rocker arm.

4.

Insert valve cages, gaskets, and valve cover plate. Position inlet valve with spring showing and outlet

valve with spring in cover recess.

5.

Assemble cover to body with notch marks lined up. Install screws but

do

not tighten.

6.

Push rocker arm in a full stroke and hold in this position to flex diaphragm.

Dkphmgm

must

k

Mxod

or

II

will

cklivor

too

much

frnl

pnrwn.

7.

lighten cover screws alternately and securely, then release rocker arm.

8.

Install pump

on

engine and

repeat

pressure test.

CHOKE

Remote

starting

engines

use

either

an

automatic electric

or

a

therm0

magnetic

choke. These chokes

are

easily

identifii

by

their outside appearance (Figure

38

and

Fig-

ure

39).

32

VALVE

AND

CAGE

ASSEMBLIES

FILTER

A

ELEMENT

.I

AMBIENT TEMP.

(OF)

CHOKE OPENING (Inches)

65

70

I

75

EO

e5

I

90

I

95

100

60

I/B

9/14

5/32

I

BOWL

U

11/64

FIGURE

37.

PUMP

ASSEMBLY

3/16

13/64

I

7/32

I

15/64 I14

50

60

.

m

75

AMBIENT TEMP. (OF)

IO

20

30

40

CHOKE OPENING

(

Inches)

114

5/16 11/32

318

7/16

15/32

112

91

16

7

CHOKE

OPENING

7-

(See

text)

MODEL

MJ B-MJ

C

\??:-

AMBIENT

TEMPERATURE('F)

68

72

76

I

80

I

84

1

88

I

92

I

%I

100

CHOKE

PLATE

MJ

C

LOOSEN

THIS

SCREW

AND

ROTATE THE

ASSEMBLY

61

-

ENTIRE COVER

CHOKE OPENING

-

INCHES

3/16 7/32

I

./4

9/32

5.'16

11/32 3'8 13'32

7'16

0

1/64 3/64 1/16 3/32

9-64

11/64

7 '64

I

.'E

Ii

I

LOOSEN THESE SCREWS

AND

ROTATE THE

ENTIRE COVER ASSEMBLY

I

FIQURE

38.

CHOKE

ADJUSTMENTS

33

WASHER

(17/64

I.D.

x

5/8

O.D.

x

1/16")

INSULATOR

WASHER

r

LIM,T

LEVER

TlNG

SOLENOID COIL

RETAINING RING

SOLENOID CORE

A076

SOLENOID

FRAME

GROUND TERMINAL

SHAKEPROOF

WASHER

GROUND LEAD

PLATE

--

WASHER

(24/64

I.D.

n

9/16

X

1/16

"

NUT

(546-18

")

2

INSERT INNER

ELECTRIC CHOKE

IN COVER TAB

FIGURE

39.

DISASSEMBLY OF ELECTRIC AND

THERMO-ELECTRIC CHOKE

Operation

and

Adjustment, Electric Choke

This choke is controlled by an electric element. Before engine starts, choke is closed. When engine has started, the generator supplies current to the heating element, which heats chokes bimetal coil.

As

coil heats,

it

winds

tighter, opening choke plate.

Under normal operation, adjust choke

so

the distance measured between choke plate and carburetor throat, Figure

38,

is

as shown in the table

and

with engine

cold.

Use straight shank end

of

a

drill bit to measure gap. The

air cleaner or flame arrester

must

be

removed for choke

adjustment.

To

adjust choke,

loosen

the

two

screws

on

end plate and rotate cover assembly.

Under

extreme

temperature conditions

it

may

be

nec-

essary to readjust choke for

best

operation. For more

choking, turn cover

clockwise;

for less choking, turn

it

counterclockwise.

Operation

and

Adjustment, Thermo-Magnetic

Choke

This choke uses a strip heating element and a heat sensitive bimetal coil in addition to magnetic solenoid. During cranking solenoid

is

energized, further closing choke.

The bimetal is calibrated

to

position choke

at

the proper

opening under

any

ambient condition. Choke is adjusted at the factory. If, for any reason, adjustment is required, use

the

following procedure:

Adjustment must

be

made with the bimetal at ambient

temperature.

Do

not

attempt adjustments until engine

has been shut down for at least one hour. Remove flame

arrester

and

adapter to

expose

choke

plate.

Loosen

screw

which

secures

the

choke

body

assembly. Refer

to Figure

36

for

correct

choke setting according to tem-

perature.

Use

a

drill

rod or shank of a

drill

bit

to

measure

choke

opening. Rotating choke

body

clockwise richens

and

counterclockwise leans the choking effect. Tighten

screw

that

secures choke

body.

Disassembly

and

Repair, Electric

and

Thermo-

Magnetic

Choke

If

choke does not operate, or will not maintain its adjustment, disassemble for repair. If choke plate will not close, check for binding, incorrect adjustment, or incorrect assembly of coil. If

it

will not open after engine starts,

check for heating. Choke should

be

warm to

the

touch

within a minute or two of engine starting. To disassemble choke refer to Figure

39.

Electric

Choke

If

choke will not heat properly, check for a broken heating coil or high resistance electrical connections. Check coil resistance with an ohmmeter. With element

at

room tem-

perature, resistance should be about

5

-

6

ohms for

12-

volt models, about 25 ohms for 24-volt models and about 16 ohms for 32-volt models. If coil is defective, replace the thermostat cover.

Thermo-Magnetic

Choke

If choke

will

not heat properly, check for broken heater wire, high-resistance connections or broken lead wires to the bimetal and heater assembly. With element at room temperature, check the heater resistance with an ohmmeter. Resistance should be about

30.6

to 37.4

ohms for a 12 volt system.

If

heater is defective, replace it with a new one. When start button is engaged, solenoid should cause spring-loaded armature to contact solenoid core.

If

this does not occur, check for broken lead wires or a

defective solenoid coil. There must

be

slack

in

lead wires between choke body and the bimetal and heater assembly. The solenoid coil resistance should

be

2.09

to 2.31

ohms in a

12

volt system.

When replacing cover on thermostat and heater assembly, be certain that the choke heater lead wires have been correctly installed

in

choke housing. Improper replacement of lead wires can cause choke assembly to malfunction.

Wires enter choke assembly through a small notch that is cut

in

edge

of

the housing. A cover holds wires in place and prevents movement when tightened. When properly installed, lead wires will hang freely under bimetal coil when choke is in either open or closed position. End of heater wire sleeve should

be

located from

1/8

inch inside choke housing to flush with inside wall.

When

assembling thermomagnetic choke, the bimetal

and heater assembly is connected

as

follows:

1.

Lead tagged G goes to ground terminal on coil

2.

Lead

tagged

H

goes

to either

of

the

H1

terminals on

solenoid.

solenoid core.

CARBURETOR

The gasoline carburetor

is

a horizontal draft type, with upturned intake horn (air silencer adapter). The carburetor consists of three major sections

-

bowl and float,

idle circuit, and load circuit. Fuel enters carburetor through inlet valve (Figure

40)

and

passes into float chamber.

To

control fuel level in the bowl, the float closes the inlet valve when fuel reaches a certain height, and opens it when fuel level drops.

CAR

BU R ET0

R

BODY

FUEL INLET

VALVE

CARBURETOR

FLOAT

-

=

z

-

FIGURE

40.

CARBURETOR

INLET

VALVE

The idle circuit (Figure 41) supplies fuel during no-load

operation and for light loads. Since throttle plate is nearly closed at no-load, intake manifold vacuum

is

high and pressure difference between manifold and float chamber causes fuel to flow through

the

idle circuit. The pressure difference draws fuel up through hollow center of main adjusting needle, through passages in carburetor body

to the idle port. Bleed holes in main adjusting needle allow

air to bleed in and mix with the fuel. When throttle is almost completely closed, fuel passes out through idle

port,

controlled by the idle adjusting needle.

As

throttle is opened to increase power, it gradually exposes idle transfer port. Fuel is also drawn out through this port.

As

engine governor opens throttle further, under

in-

creased load, the increased air flow through carburetor produces a low pressure at the venturi (narrow section of carburetor throat). This pressure drop draws fuel

up

the main nozzle to

be

mixed with air at the nozzle opening. This is the load circuit (Figure 41). The main adjust needle controls its fuel delivery.

.

At

the same time, because throttle

is

open, manifold

vacuum decreases

so

idle circuit becomes less effective.

In

a

certain

range,

the

two

circuits Mend, both delivering

fuel; but, as load is increased, load circuit takes over. Whenever load is increased,

with

load circuit in operation,

the governor opens throttle to deliver more fuel.

Main

nozzle

will

not

Immediately

deliver

this

increased

fuel

be-

cause

of

the

jet

controlled

by

adjusting needle.

To

reduce

power

lag when load is suddenly increased, a

by-pass

jet around the metering jet delivers fuel to nozzle until

main jet

can

supply the increased demand.

35

*NOTE: VENT EXTENDS THROUGH

AIR ,CLEAN€

R

ADAPTER

ON

LATER MODELS

IDLE

JET

OPERATING

IDLE ADJUST

NEEDLE

CHOKE VALVE

*:%%

IDLE JET OPERATING

FIGURE 41.

CARBURETOR

CIRCUITS

Adjustment

Adjusting carburetor means obtaining the correct fuel-

to-air mixture for smooth, efficient operation. Carburetor

should

be

adjusted in

two

steps - first load adjustment

and then idle adjustment.

If

carbumtor

Is

c0mpkt.l~

out

of

adjuslment

so

enQlne

Will

not

run,

opmn

both

nndle

valvor

1

to

142

turns

ofl

their

soots

to

pennit

starling.

Do

not

fm

nmlle

valvrr

rgalnrt

their

seats.

This

will

kndthrnmlk.

Before adjusting carburetor,

be

sure ignition system is

working

properly

and governor is adjusted. Allow engine

to warm up before making adjustment.

.

1.

Apply

a

full

load to the generator.

2.

Carefully turn main adjustment

in

until

speed

drops

slightly below normal. Then turn needle out until

speed

retums to

normal.

3.

With

no

load

on

the engine,

turn

idle

adjustment

out

until engine

speed

drops slightly below normal. Then

turn needle in until

speed

returns to normal.

Alternate Method,

Use

When Loading Engine is

Noi

Posslbie:

1.

Start engine and allow it to warm up.

2.

Manually close throttle to slow engine down to about 600 - 700

rpm.

.

3. Set idle adjustment screw for even operation (so engine is firing on all cylinders and running smoothly).

4.

Release governor mechanism allowing engine to accelerate. If engine accelerates evenly and without a lag, main adjustment is correct.

If

not, adjust needle

outward about

1/2

turn and agah slow down engine and release the mechanism. Continue until engine accelerates evenly and without a time lag after releasing governor.

With carburetor and governor adjusted, set throttle stop screw (Figure

42)

to

allow

1/32”

clearance to the stop pin with engine operating at no load. This improves governor stability when a large load is suddenly removed.

THROTTLE

STOP SCREW

r

MAIN FUEL

AD JU STMEM

FUEL IDLE

ADJUSTMENT

THIS

DISTANCE

INCH AT NO LOAD

PRIOR

TO

SPEC

R

DISTANCE

AT

NO

LOA0

BEGIN

SPEC

R

MAIN FUEL

M

JUSTMENT

A

NYLON ROD

EXTENDING

DOWNTHROUGH LOWER

SHROUD PAN

.

Removal and Disassembly

1.

Remove fuel line, governor linkage and electric choke wires.

2.

Remove air silencer adapter from the carburetor.

3.

Remove 2 carburetor mounting nuts and remove carburetor.

4.

Remove choke coil from carburetor.

5.

Remove float bowl nut and pull off bowl.

6.

Remove the float pin and float.

7.

Lift out float valve and unscrew its seat.

8.

Remove no-load adjusting needle and spring.

9. Remove load-adjusting needle and spring.

10.

Remove throttle plate screws and plate, and pull out throttle shaft.

11.

Remove choke plate screws and plate, and pull out choke shaft.

Cleaning and Repair

To

clean carburetor, soak all components thoroughly in

a

good

carburetor cleaner, following cleaner manufacturer’s instructions. Be sure all deposits are cleaned from carburetor bore, especially

in

the area

of

the throttle

valve.

Blow

out passages with compressed air. If pos-

sible, avoid using wire to clean out passages. Check adjusting needles and nozzle for damage. If float

is loaded with fuel or damaged, replace. Float should

fit

freely on its pin without binding. Invert carburetor

body

and measure float level (Figure

43).

If necessary, bend small lip on float to adjust float level.

.

THIS

DIMENSION

SHOULD

BE

11/64

Check choke and throttle shafts for excessive side play and replace if necessary.

Do

not remove teflon coating on the throttle shaft. Coating reduces wear and friction between the shaft and carburetor body.

Assembly and Installation

1.

Install throttle shaft and plate using new screws

and

lockwashers. Install with plate bevel mated to the carburetor body. On plates marked with the letter C, install

with

mark

on

side toward idle port when viewed from manifold mounting flange end of carburetor.

To

center plate, back

off

idle stop screw,

close throttle, and seat plate

by

tapping

it

with a small

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

screwdriver; then tighten the

two

screws.

Install choke shaft and plate. Center plate in same manner as throttle plate (step

1).

Use new screws

and lockwashers. Install main nozzle, making sure

it

seats in body

casting. Install inlet valve seat and valve. Install float and float pin. Center pin

so

float bowl

does not ride against it. Check float level with carburetor casting inverted.

See

Figure

43.

Install bowl ring gasket, bowl, and bowl nut. Make sure that bowl is centered

in

gasket, and tighten nut

securely. Install load adjusting needle with its spring.

Turn

in

until

it

seats, and back out 1 to

1-1/2

turns.

Install idle adjusting screw finger tight. Then back

out

1

to

1-1/2

turns. Install choke and adjust. Install air horn assembly and gasket. Install carburetor on engine, and connect gasoline

inlet, governor mechanism, breather hose, and choke wires.

13.

Install

air

silencer

or

flame arrester.

AIR SILENCER AND FLAME

ARRESTER

Metal

filter

element serves

also

as

a

flame

arrester.

As

a

safety precaution

do

not

substitute

with

non-metal

air

cleaner.

Clean

regularly

and

assemble

dry. Replace

ele-

ment if damaged.

FlQURE

43.

FLOAT LEVEL

37

EXHAUST

SYSTEM

The exhaust system is normally supplied by user, and

installed in the field. However, importance of

a

correct

exhaust system cannot be over emphasized.

A

poor or

clogged system can cause

low

power, overheating, and

eventual engine damage. The effect of a poor exhaust

system is to increase back pressure at engine, reducing efficiency. If excessive back pressure is suspected, test engine according to the following procedure.

I.

1

.*--

LATER

MODELS

FIGURE

44.

AIR

SILENCER

Testing

Install an adapter or tee in exhaust line next to manifold.

Connect a manometer or pressure gauge to adapter.

If

there is a condensation trap next to manifold, this can

be

used for manometer connection. Run engine under

full-load and observe manometer. See Figure

45

for max-

imum values. If reading

is

higher, exhaust system should

either

be

disassembled and cleaned

or

altered to reduce

back pressure.

WARNING

inhalation

of

exhaust gases might re-

n

sult

in

serious personal injury

or

death. Pipe exhaust outside the hull and do

NOT

ter-

minate exhaust pipe near any window

or

bulkhead

door openings.

Units of

Full

No

Measurement Load Load

2

Cyllnder

Inches

of

Water 27

5.1

inches

of

Mercury

2

316

Ounces

15.6

02.

2.9 02.

4

Cyllnder

Inches

of

Water 27

4.7

Inches

of

Mercury

2

113

Ounces 15.6

oz.

2.7

02.

FIGURE

45.

MANOMETER

.

Governor

System

Governor system controls engine speed with and without load. The system consists of a governor cup with steel flyballs on the chamshaft, a yoke, shaft, and arm, gov-

ernor spring and adjusting screw, and linkage to

carburetor. Variations in engine speed change the position of gov-

ernor cup on its shaft. This change is transmitted by the

shaft, arm, and linkage to carburetor throttle lever. En-

gine speed is determined by tension

on

the governor

spring. Sensitivity (speed drop from no-load to full-load)

is controlled by the number of spring coils used. More

coils give less speed drop from no-load to full-load

(greater Sensitivity).

MAINTENANCE

Periodically lubricate governor linkage with lubricating graphite or light non-gumming oil. Also, inspect governor linkage for binding or excessive slack or wear.

Adjustments

Prior to Spec

R,

both governed speed and governor sensitivity are adjusted with the stud and nut on the front of engine air housing (Figure

46).

Beginning with Spec

R,

sensitivity is adjusted with an adjusting ratchet.

Speed

Adjusfment (Prior

to

Spec

R):

To

adjust gov-

erned

speed,

hold governor spring stud in position and

turn governor spring nut with a wrench.

A

mechanical

tachometer may

be

used for speed adjustment.

Sensitivity Adjustment (Prior to

Spec

R):

To

adjust sensitivity, turn governor spring stud; turning counterclockwise gives more sensitivity (less speed drop). If governor is too sensitive, a hunting condition occurs (alternate increasing and decreasing speed). Adjust for maximum sensitivity without hunting. After a sensitivity adjustment, speed may require readjustment.

Speed Adjustment

(Begin

Spec

R):

Adjust engine

speed

(RPM)

by

turning governor speed adjusting nut,

Figure

46.

Turn nut clockwise to increase speed, coun-

terclockwise to decrease speed.

SensHivify Adjustment (Begin Spec

R):

Sensitivity (no-

load to full-load speed drop) is adjusted by turning sensitivity-adjusting ratchet nut accessible through hole in side of blower housing. If speed drops too much when full load is applied, turn ratchet nut counterclockwise to

increase spring tension and compensate for reduced

rpm. An over-sensitive adjustment, approaching no

speed drop when load is applied, may result in a hunting condition (alternate increase and decrease in speed).

After adjusting speed and sensitivity, secure speed stud

lock nut.

If governor is too sensitive or not sensitive enough, and

cannot

be

adjusted with stud or ratchet, the sensitivity

can

be

adjusted by changing spring attachment on the governor arm. Moving this point further from the governor shaft decreases governor sensitivity.

I

WARNING

1

EXHAUST

GAS

IS

DEADLY!

Exhaust gases contain carbon monoxide, a polsonous gas that might cause unconsciousness and death.

It

is an odorless and colorless gas formed during

combustlon

of

hydrocarbon

fuels.

Symptoms

of

carbon monoxlde poisoning

are:

Dizziness Vomiting Headache Muscular

Twitching

Weakness and Sleepiness

Throbbing in Temples

If

you experience any

of

these symptoms,

get

out

Into fresh air fmrnedlately,

shut down the unit and do

not

use

until

It

has been Inspected.

The best protectlon against carbon monoxide lnhalation is proper insfallaflon and regular, frequent lnspecflonr

of

the complete exhaust system.

lf

you notice

a change

In

the

sound

or appearance

of

exhaust system, shut the

unlt

down imrnedlafely and have It inspected and repalred at once by a competent mechanic.

39

r/

ADJUSTING NUT

TURN

FOR

MINIMUM SPEED

OP. THEN ADJUST SPEED NUT

PRIOR

TO SPEC R

dd

GOVERNOR

ARM SPRING SPEED

STUD

'SENSITIVITY

ADJUSTING

BEGIN

SPEC.

R

RATCHET

FIQURE

1.

GOVERNOR

ADJUSTMENTS

Ignition

System

RJC

The ignition system in the

RJC

engine uses a battery ignition system with automotive distributor to produce and distribute spark (Figure

47).

The ignition system includes ignition coil, distributor with

spark advance and breaker points, and spark plugs. For satisfactory performance of ignition system all com-

ponents must

be

in good condition, and the spark must be properly timed. Hard starting, low power, and erratic operation can often be caused by faulty ignition. If poor ignition

is

suspected, the first thing to do is to determine

if the ignition system is actually at fault.

A

simple oper-

ational test will determine this.

Remove spark plugs, install ignition wire, and lay plug

on grounded engine metal. Crank engine and watch plug.

Strong blue spark indicates high current in ignition sys-

tem; weak, yellow, or no spark indicates low current.

Poor ignition can be caused by defective breaker points, coil, condenser, or wiring.

A

weak spark on only one plug

indicates a defective plug or high tension wire.

Maintenance of ignition system should include oiling the

distributor, cleaning and adjusting breaker points, spark

plugs, checking ignition timing, and general inspection of

the ignition system wiring.

At regular intervals, add three to five drops of medium

engine oil to distributor oiler (Figure

48).

Add one drop

of light engine oil to breaker arm hinge pin and three to

five drops to felt in

top

of shaft and to governor weight

pivots. Lightly grease each lobe of breaker cam.

Do

not

over-lubricate the distributor.

Adjust breaker points by rotating crankshaft until rubbing block is on high point of cam. Gap should

be

0.020

inch. inspect points for dirt or pitting. Dirty points can be cleaned, but pitted points should

be

replaced.

Inspect distributor for cracks, carbon, corroded or excessively burned inserts. In normal use, vertical surfaces of cap inserts become slightly burned. Clean but do not file the inserts.

If

they are excessively burned, replace

distributor cap. Clean rotor and inspect for cracks.

Se

verely burned

or

pitted rotors should be replaced.

Time ignition by adjusting distributor

so

each plug fires

at

25"

BTC (before top dead center)

35"

BTC for gas-

eous fuel on the compression stroke. Ignition system can

be

timed with the engine stopped or running. Always clean and adjust breaker points before timing.

TIMING PROCEDURE - ENGINE

STOPPED

1.

Disconnect low voltage lead to distributor. Connect a test lamp (with battery) to light when breaker points close.

2.

Remove number one spark plug and rotate flywheel clockwise until test lamp goes out. Breaker points are now open. This

is

the igniting point.

3.

If the

"TC"

mark

pointer are aligned,

SPARK

PLUGS

on flywheel and ignition timing

timing is correct.

ARM

RUBBING

uA,58

BLOCK

ON

HIGH

POINT

OF

CAM

FIGURE

48.

BREAKER

POINT

GAP

4.

If timing needs correction, align flywheel TC mark and timing pointer. Loosen distributor body and rotate

it

(clockwise if ignition occurred early, counterclockwise if

late) until the light goes out.

5.

Tighten distributor clamp and recheck timing step

3.

If timing still does not occur at the correct point, repeat step

4.

TIMING

PROCEDURE

-

ENGINE RUNNING

1.

Connect an automotive timing light to number one spark plug (follow manufacturer's instructions).

2.

Run engine at rated speed. Aim timing light at timing pointer. If light flashes as pointer and timing mark are aligned, timing is correct.

3.

To

adjust timing, loosen distributor body clamp and

rotate distributor slowly. If timing

is

early (mark is at right of pointer) rotate distributor clockwise. When pointer and marks are aligned, tighten distributor.

Fluctuating timing marks

usually

mean a defective distributor.

Check

for

pitted

or

misaligned points, inconect point spring ten-

sion,

worn

(or

loose)

breaker plate,

or

worn

distributor shafl

bushing.

DISTRIBUTOR

*

The distributor's function is threefold.

It

opens the

breaker points at

the

proper time, advances timing au-

tomatically, and sends current to the proper plug.

Testing

Test distributors on a commercial distributor tester (following equipment manufacturer's instructions). Centrifugal advance mechanism should

be

in good working

condition. The cam dwell angle should

be

51

k

3"

(never

set breaker gap

by

cam dwell). If cam dwell is outside the above limits with proper point gap, check for worn distributor cam.

If a distributor tester is not available, follow this procedure:

To check spark advance, remove distributor tower and

rotate the rotor several degrees clockwise. If the automatic advance is working properly, rotor will return to its original position when released. If

it

binds, overhaul the

distributor.

Inspect breaker points to determine if movable contact turns freely on its pivot.

Use a spring scale (Figure

49)

to measure point spring

tension. Tension should

be

17-20

ounces with rubbing

block

off

the cam. Greater tension causes excess wear;

less tension causes point bounce.

Disassembly

1.

Remove distributor

cap

and primary lead from dis-

2.

Mark

position

of

distributor

body

and rotor position

tributor primary terminal (Figure

50).

for reassembly without changing timing.

RaURE

49.

POINT

SPRING

TENWN

42

PRIMARY

DISTRIBUTOR

-

CLAMP

FIGURE

50.

DISTRIBUTOR

CENTRIFUGAL ADVANCE

3.

Remove distributor hold-down capscrew and pull out

distributor.

4.

Remove three screws holding breaker plate to dis-

5.

Lift breaker arm

off

its hinge.

6.

Rotate breaker plate

45"

counterclockwise and lift

it

tributor housing and loosen primary terminal.

out.

7.

Remove

two

centrifugal advance springs.

8.

Remove cam retaining spring clip holding cam to

shaft and lift out the cam. The advance weights are

now free and can

be

removed.

9.

File

off

peened end of drive gear retaining pin and

punch

out

the pin. Then remove the gear and pull

shaft out through the distributor body.

10.

If

necessary, press the

two

bronze bearings out of

the distributor

body.

1

1.

Clean all parts (except condenser, points, bushings) in light cleaning solvent. Inspect centrifugal advance parts and replace any that appear worn or otherwise damaged. Inspect cam and shaft for wear.

If

either

is scored, replace it.

To

check for bearing wear, measure side play at the top

of

cam

with adial indicator. Mount indicator on distributor

body and measure side play

by

pulling shaft directly away from indicator with a force of about five pounds. If side play exceeds

.005

inch, bearings

must

be

replaced.

ONAN

does not recommend field replacement of bronze

shaft

bearings

unless

special

sizing

and driving equip

mentis

available.

This

can

be

done

by

an

Autdite

Service

station.

Assembly

1.

Inspect upper shaft

thrust

washer and install shaft

assembly.

2.

Install lower shaft thrust washer and drive gear. In-

3.

Distributor shaft end play should be

.003

inch to

.010

.

inch (Figure

51).

If

end play is less, tap lower end of

distributor shaft lightly with a soft hammer.

If

too

great, check thrust washer installation or reinstall the gear.

sert drive gear retainer pin and peen ends.

*\\

ON SHAFT\-

-

\

-g

GAUGE

BETWEEN

GEAR

AND

THRUST

WASHER

FlQURE

51.

DISTRIBUTOR

SHAFT

END

PLAY

CHECK

4.

Set centrifugal advance weights

into

place and install

cam.

Be

sure cam weight pivots fit into hole in each

weight.

5.

Insert

cam

retainer spring clip and install weight

springs.

6.

Install

breaker

plate.

7.

Mount

movable

breaker

point.

Insert pint sprhg

be-

tween end of terminal stud and square metal washer. Then tighten the primary terminal.

8.

Align breaker points by bending stationary contact bracket.

43

9,

10.

Check breaker spring tension with a spring scale hooked at the movable arm contact and rubbing block off cam. Hold at right angles to contact surfaces (Figure

49).

Tension should be

17

to

20

ounces. If not, adjust it by loosening screw holding end of contact spring and installing spacing washer or sliding end of the spring

in

or out.

Rotate drive shaft to obtain maximum breaker gap

and set gap for

0.020

inch (Figure

48).

Installation

Install distributor in exactly the same position prior to removal. The rotor should be

1

/8

turn counterclockwise

from previous installed position to allow gears to mesh.

After installing, perform steps

4,

5,

and 6 below.

If exact position of distributor body and rotor were not recorded (before removal) or if crankshaft was rotated, follow procedure outlined below.

1.

Remove spark plug from No. 1 cylinder. Place a finger

over the plug port and rotate flywheel clockwise until

cylinder builds up pressure. Continue rotating until flywheel "TC" mark aligns with timing pointer.

2.

Install rotor on distributor shaft and the O-ring on the body.

3.

While holding distributor in the position shown in Figure

52

and the rotor

1/8

turn counterclockwise from

position shown, seat the distributor.

It

may

be

necessary to turn rotor slightly to mesh distributor and camshaft gears. The rotor will move about

1/8

turn

as gears mesh and should

be

in the position shown

in Figure

52

when distributor is in place. If it is not, pull distributor upward until gears do not mesh and re-install.

TCH

POSITION

OF

DISTRIBUTOR WHEN

NO.

I

CYLINDER

IS

AT

TOP

CENTER

(COW

PRESSION

STROKE)

RQURE

52.

DISTRIm

I"rALL"

po8moN

4.

Install distributor clamp screw.

5.

If spark plug leads were removed from distributor cap,

connect them in

the

1-2-4-3

firing order (Figure

47).

6.

Time ignition system.

IGNITION

COIL

RJC

ignition coils are standard automotive type mounted on the engine. Normal maintenance includes inspecting, tightening, and cleaning the primary and secondary terminals.

Coils can be tested on standard automotive testers or by checking primary and secondary winding resistance. Resistance from high tension terminal to

the

ground

(-)

'

terminal should

be

7,000

to

10,000

ohm; resistance

be-

tween the primary terminals should be about l ohm.

Check coil failure by simply disconnecting high tension lead at the distributor. Hold about

1/4

inch from block

and crank engine.

A

strong spark between lead and en-

gine indicates coil is operating. No spark indicates coil,

points, or control circuit to the coil are defective. Before discarding coil, check for voltage between coil terminal and ground while cranking engine. Inspect breaker points.

If

coil effectiveness is

in

doubt after tests replace

it.

Ignition capacitor mounts on outer side of distributor. If suspected of being defective, test and replace

if

nec-

essary. Capacitance should

be

.25

to

.28

mfd.

-

HIGH

TENSION

LEADS

Inspect ignition leads for cracks

or

breaks

in

insulation

that may weaken the

current

before it reaches

a

plug.

A

ground wire touching metal at some point may make operation unsatisfactory.

SPARK

PLUG

Engine misfire or generally poor operation

is

often

caused

by a

spark

plug in poor condition or

with

the wrong gap

setting. Remove

spark

plug and carefully check for the

following conditions:

Porcelain

insulator cracked or coated with

oil.

Electrodes

burned

or

worn

away.

0

Wrong gap setting.

If porcelain insulator

is

cracked

or

broken

or

if

the

elec-

trodes

are

badly

worn

or

burned,

replace

spark

plug

with

a

new

one.

If

not,

it

can

probably

be

restored to good operating

condition

by

the following steps:

1.

Degrease wet

or

oily plug

and

dry thoroughly.

2.

File center electrode to a flat surface.

3.

Adjust gap to

0.035

inch. Use a round wire gauge

for

4.

Install plug. Tighten to torque value

of

25-30

ft.-lb.

5.

Always use new gaskets.

more

accurate measurement (Figure

53).

n

FIGURE

53.

SPARK

PLUG

ADJUSTMENT

45

q

5-

Ignition

System

MJB,

MJC

TO

CONTROL

BOX

TERM.

BLOCK

All

models are equipped with a 12-volt battery ignition system. The function of this system is to provide a spark in each cylinder at the correct time

to

ignite the fuel air

mixture.

All

systems use suppressed ignition components to minimize radio interference. The 4-cylinder model (MJC) uses a battery ignition system with dual breaker points and ignition coils.

TO

CONTROL

BOX

TERM.

BLOCK

TESTING

The most complete test for an ignition system is to check the final result

-

spark on at spark plugs. Remove each plug in turn, install ignition wire to that plug and hold plug base against

a

piece of bare engine metal. Crank engine

and watch the spark.

A

good blue spark indicates a healthy ignition system; a weak or yellow spark, or no spark indicates a poor ignition system. The defect can be caused by defective breaker points, coil, condenser, or wiring.

A

good spark on all but one cylinder indicates

a

defective spark plug or defective high tension wire.

MJB

IGNITION

SYSTEM

This ignition system uses battery ignition and a single

4-

volt coil to fire both spark plugs simultaneously (Figure

54). This means one spark plug fires on exhaust stroke

while the other is firing at the end of the compression

stroke.

A

spark advance on breaker point mechanism

advances spark from 5" ATC (after top center) when

cranked to 25" BTC (before top center) when running at rated speed and using gasoline.

*

I

Maintenance

Operating with a weak spark is detrimental to the engine,

so

periodic service is extremely important. Periodic main-

tenance should include:

1.

Checking the ignition breaker point gap.

2. Checking and cleaning spark plugs.

3.

Inspecting both low and hi voltage wiring.

4.

Checking the ignition timing.

To adjust breaker gap, rotate crankshaft clockwise until 55" ATC mark on flywheel matches the timing pointer (Figure 55). This is the point of maximum breaker opening.

Breaker point gap should

be

0.020

inch; check it with a feeler gauge. If gap is not correct, loosen adjustment screw and move the stationary contact. Tighten screw and recheck the gap.

When adjusting points, check to

be

sure they are clean and not pitted. If necessary, clean points with paper or gauze tape. If they are defective or excessively pitted, replace them.

L-,,,J

I

IGNITION

FMURE

54.

MJB

lo"

SYSTEM

46

.

FIGURE

55.

TIMING

MARKS

Timing The engine can be timed either stopped or running at

rated speed. With engine stopped, timing should be set for ignition at

5"

ATC;

with engine running at rated speed,

25"

BTC. Always adjust breaker point gap before timing

the ignition. Time the engine as follows:

Engine

Stopped:

1.

Remove breaker box cover. Disconnect lead to ignition points and install a continuity test lamp and battery

so

lamp lights when points are closed.

2.

Rotate flywheel clockwise until

TC

mark on flywheel

approaches timing indicator (Figure

55).

3.

Slowly rotate flywheel clockwise until light goes out indicating that the points have opened. This is the ignition point. If timing is

correct,

ignition will occur at

5"

ATC.

4.

If

ignition timing isn't correct, align

5"

ATC mark and timing pointer, then loosen breaker plate capscrews and rotate plate

so

the light goes out. Rotating clockwise advances timing, counterclockwise retards timing.

5.

Tighten plate and check timing (step

3).

If timing

is

not

correct,

adjust plate again. If it is correct reconnect

ignition

lead

and replace cover.

Englne Running:

1.

Install an automotive timing light

on

either of the spark

plug leads.

2.

Run engine

at

rated

speed

and check timing with the

light. If timing is

incorrect,

loosen

breaker

plate mount-

ing

screws

and

correct

by

rotating

the

plate.

Rotating

dockwise

advances timing; rotating counterdockwise

retards timing. Tighten

plate

before rechecking the

timing point.

3.

Adjust thing, retighten breaker plate, and recheck the ignition point

gap.

If

ignition point gap cannot be adjusted to specifications,

either timing gear

or

camshaft gear is incorrectly in-

stalled, or the centrifugal advance mechanism is defec-

tive and breaker mechanism must be disassembled

for

repair.

Breaker

Points

Ignition breaker points (Figure

56)

operate from a cam

located on the timing or start-disconnect gear. This gear

is

driven by the camshaft gear.

Disassembly:

1.

Disconnect battery to, prevent accidental shorts.

2.

Remove breaker box cover and disconnect wires from the start-disconnect switch (if used) and ignition breaker points.

3.

Remove the two capscrews that hold breaker plate assembly, and pull

off

the plate.

4.

Pull

out cam and weight assembly. Be careful not to

lose spacer mounted

on

gear shaft.

5.

To

disassemble breaker plate assembly, remove condenser and points and pull out the plunger and plunger diaphragm.

TO

ADJUST

D ,IGNITION TIMING

I%\\

SET IGNITION

BREAKER

,I

hk

POINT GAP

KEEP

THIS

01

L

HOLE

'

CI

FAR

SET

DISCONNECT

SWITCH

G,$P AT

BACK

SIDE

OF

IGNITION

BREAKER PLATE

0.020

I

FIGURE

56.

BREAKER

POINTS

Repair:

Thoroughly clean gear and cam assembly. Weights should move freely without catching in either end position. Inspect gear ramp for notches or other defects. If any part

of

cam, weight, and gear assembly sticks, the

completeassembly, including springs, must be replaced.

If

cam

is

loose on gear

shaft,

the complete assembly

must be replaced. Clean and inspect bearing surfaces

47

in breaker plate and gear case; be sure to clean the oil

trickle holes

to

these bearings. Check oil spray hole in

gearcase to be sure

it

is open.

If

breaker points

will

not maintain the proper gap, check for excess wear in both cam and ignition breaker plunger.

Assembly:

1.

Install springs on weight assemblies. Install cam on

the gear shaft, being sure to align timing marks (Figure

58),

and install the cam spring.

2.

Install spacer and thrust washer on gear shaft assembly, and install assembly into the gearcase. Match timing marks on timing gear and camshaft gear (Figure

58).

3.

Install spring and plunger on the end

of

shaft.

4. Install the breaker plate. Install ignition plunger, dia-

phragm, and diaphragm cup (Figure

59).

5.

Install start-disconnect diaphragm and plunger, when used, and install start-disconnect breaker points.

6.

Adjust start-disconnect breaker point gap (if used) to

.020

inch.

7.

Install ignition breaker points and adjust gap.

8.

Time ignition.

Lfore

r@Wlng

start

dlrconnect point

gap,

rotate

engine

crank-

shafi

a

few

dogroes counterclockwise. This will enable

start

dis-

connect

mechanism

to

assume

a

normal position.

Condenser

The

0.3

mfd condenser mounted on breaker plate aids primary field breakdown when points open and prolongs breaker point life

by

reducing the arc across them.

A

defective condenser causes a weak spark and rapid breaker point wear. Use a standard commercial condenser checker to test the condenser for leakage, openings or grounding. If no tester is available, check for

shorts or defective leads and replace the condenser if you suspect

it

is defective.

Coil

If spark is weak or there is no spark, and breaker points are clean and properly adjusted, test coil for possible defects.

As

a general test

of

the coil, disconnect spark plug leads, ground one, hold the other lead 1/4 inch from engine. Crank the engine.

A

good spark indicates coil

is

operating.

Further tests of the coil are as follows:

1.

With an ohmmeter check resistance of the coil wind-

ings. Normal resistance readings range from

0.5

to

2

ohms for primary winding and from

4000

-

10000 ohms for the secondary winding. Extremely low resistance usually indicates a shorted winding and extremely high resistance usually indicates an open

in

the winding.

The

rl-vott

coils can

be tested

on

a

6-

VOM

tester. However,

a

7bvoM

tester

will

destroy

the

coil

in

a

few

seconds.

2.

If

a coil passes

all

the abovementioned tests and fails

to operate,

it

should then

be

tested on a standard

coil

and winding tester for which test data

is

available.

“0”

MARK

ON

“0”

ON

IGNITION

BE

ALIGNED

TIMING GEAR

.

’

“0”

MARK

ON

!

I

B,E ALIGNED

CAMSHAFT GEAR

S

TIMING

WEIGHT

il

FIQURE

I.

TIMING

MARKS

18

t

IGNITION

BREAKER

PLATE

._

DIAPHRAGM CUP

At

regular intervals, add 3 to 5 drops

of

clean medium

grade engine oil

to

oiler on distributor. Add 1 drop

of

light engine oil40 breaker arm hinge pin and 3 to 5 drops

to

the

centrifugal weight pivots.

Wipe

grease

lightly

onto

each lobe of the breaker cam.

Do

not over lubricate

distributor.

To

adjust breaker points, remove distributor cap and rotate the crankshaft to get maximum breaker gap. The gap should be

0.020

inch. At the same time, inspect

points for dirt or pitting. Dirty points can be cleaned with tape and chlorothene.

But if points are excessively pitted, they must be

replaced.

FIGURE

59.

IGNITION PLUNGER

Timing

MJC

IGNITION

SYSTEM

The

MJC

engine uses a radio-suppressed battery ignition system with dual breaker points to produce and distribute spark voltage to the four cylinders (Figure

60).

The ignition system includes

two

ignition coils, distributor

with spark advance and

two

sets of breaker points, and

two spark plugs. Breaker point set

No. 1 fires cylinders

1

and

4;

point set No. 2 fires cylinders 2 and

3.

(See

Figure

60).

,Maintenance

Periodic maintenance of the

MJC

ignition system should include oiling the distributor, cleaning and adjusting breaker points, checking ignition timing, cleaning and ad-

justing spark plugs, and general inspection of ignition

system wiring.

Ignition timing means adjusting distributor

so

the spark

for each cylinder fires at the correct

time

for maximum

power

(25"

BTC

of each compression stroke).

The

MJC

ignition system may be timed either with the

engine stopped or running. But before timing ignition,

be

sure

both

sets of breaker points are clean and properly

adjusted. Breaker point set

No.

1

opens to fire cylinders

1

and 4 simultaneously and point set

No. 2 opens to fire

cylinders

2

and 3 simultaneously. Time engine as follows:

Engine

Stopped:

1.

Disconnect

low

voltage lead to distributor and connect

a test lamp and battery

so

lamp lights when the

No.

1

set of breaker points are closed.

2.

Remove spark plug from

No.

1

cylinder and rotate flywheel clockwise until air is forced out of the spark plug hole (compression stroke).

DISTRIBUTOR

IGNITION

COIL

IGNITION

RESISTOR

HIGH

WA~

TEMP.

J

CUT

OFF

SWITCH

'

RQURE

60.

MJC

MNmON

SYSTEM

49

I

CAM

-

FIGURE

61.

POINT

ADJUSThlENT

3.

Continue rotating the flywheel slowly until test lamp goes out, indicating that the breaker points have opened. This is the ignition point. If TC mark on fly-

wheel and ignition timing pointer are aligned, timing

is

correct;

if

not, distributor will have to

be

adjusted.

4.

To correct timing, align flywheel TC mark and timing

pointer. Then loosen distributor body and rotate

it

(clockwise if ignition occurred early, and counterclockwise if late), until light goes out.

5. Retighten distributor body in new position and recheck timing, step

3.

If timing still does not occur at the

correct point, repeat step

4.

6.

The

No.

2 set of points should be properly timed to

open if the gap is correct

(0.020

inch) and

No.

1

set of points has been properly adjusted. However, they may

be

checked for proper timing by placing a timing mark on the flywheel, 180" from the TC mark. Then repeat steps 1-5, substituting cylinder 2 for cylinder

1

and the new timing mark for TC. Later flywheels have

BC

(Bottom Center) mark.

Engine

Running:

1.

Install an automotive timing light on spark plug for

No.

1 cylinder following the manufacturer's instructions.

2.

Run engine at rated speed. Aim the flashing timing

light toward the flywheel.

3.

If timing pointer on gear cover indicates 25" BTC,

timing

is

correct. If not,

loosen

distributor body clamp and rotate distributor clockwise to retard the ignition point. Tighten distributor in its mount and recheck timing with the light.

4.

The

No.

1 set of breaker points fires cylinders 1 and

4.

Breaker point set No. 2 fires cylinders 2 and 3 and should be properly timed to open if gap is correct (0.020 inch). The timing may be checked by placing a timing mark

on

flywheel, 180" from the

25"

BTC mark

(1

55"

ATC). Then repeat steps

1

-

3,

substituting cyl-

inder

2

for cylinder 1 and the new timing mark for 25"

BTC.

If

relative

position of timing marks

do

not

remaln

steady,

distributor

is probably

defrctive.

This can

be

caused by pitted

or

miaaligned

breaker points,

by

incorrect breaker point rpring tension,

or

by

worn

or

lowe

breaker

plate,

dirMbutor

shaft,

or

burhlng.

BREAKER

ARM

AT CONTACT

50

Distributor The distributor serves three functions.

It

contains and opens breaker points at the proper time, provides an automatic spark advance mechanism, and serves the

two coils which supply high voltage to spark plugs.

Testing:

The point opening should be adjusted to

0.020

inch.

I

Thoroughly inspect breaker points and check to be sure the movable contact turns freely on its pivot.

Using a spring scale, measure tension of the points as they break contact. Tension should be

17

to

20

ounces.

If it is greater, it causes excess wear;

if

less, the contact

will bounce. See step

9,

subsection

D,

distributor as-

sembly, to adjust tension.

Removal and Disassembly:

1.

Remove distributor cap by removing the three

2.

Remove the two primary leads from distributor

mounting screws.

terminals.

3.

Remove the two coil leads from breaker

box

cover

adapter.

4.

Record position of the distributor body for easier assembly.

5.

Remove distributor hold down capscrew and pull distributor out of crankcase.

6.

Remove the three screws holding breaker plate

to

distributor housing and loosen primary lead mounting terminals.

7.

Lift breaker arms off their pivot pins.

PRIMARY

TERMINAL

\

8.

Rotate breaker plate counterclockwise about

45"

and pull

it

out

of

distributor body.

9.

Remove

the

two

centrifugal advance springs.

10.

Remove spring clip (cam retaining spring) holding cam to drive shaft and lift out the cam. The weights are now free and can be lifted out.

11.

If

necessary, press the two bronze bearings out

of

distributor body.

To

check for bearing wear, see

Repair.

Repair:

Clean all disassembled components except the condenser, breaker points, and bushings in light cleaning solvent. When dry, inspect all components. Inspect centrifugal advance component for signs of wear, and re-

place any that appear worn or otherwise damaged. Inspect cam and shaft for wear or score marks. If either

is scored, replace

it.

To

check for excess bearing wear, set the drive shaft

into body and measure side play at top of cam with a

dial indicator. Mount indicator on distributor body, and measure side play that occurs when pulling shaft directly away from indicator with a force of about

5

pounds. Side

play should be less than

.005

inch. If not, bearings must be replaced. But, because of the great care that should be exercised during replacement and a special driver required

to

size the bearings correctly,

ONAN

does not recommend field replacement of bronze shaft bearings unless the special equipment is available. An authorized service station can do this work.

Assembly:

1.

Install shaft assembly with upper drive shaft thrust washer in distributor body.

2.

Install lower drive shaft thrust washer and drive gear. Install a pin through drive gear and shaft and peen

it

into place.

CAM

RETAINING

fl

CENTRIFUGAL

ADVANCE

SPRING

CAM AND STOP PLATE

CENTRIFUGAL

ADVANCE

WEIGHTS

FIGURE

83.

DISTRIBUTOR

ASSEMBLY

51

3.

Check drive shaft end play. It should be between

.003

inch and

,010

inch. If end play is too small, tap

lower end of distributor drive shaft lightly with a

soft

hammer to increase play. If

it

is too great, check

thrust washer installation or reinstall the gear (Figure

64).

Insfallafion,

Distributor;

If you know the position of the distributor when removed and the crankshaft was not moved after distributor removal, distributor can be installed in exactly the same position. After installing, perform steps

3,

4,

5,

and 6 below.

If

exact position

of

both distributor body and rotor were not recorded or if the crankshaft was rotated, follow the complete procedure below.

Po"NE?HEgYN

1.

Remove sDark Dlua from

No.

1

cvlinder. Place a finaer

-

~EELER

GAUGE

BETWEEN

GEAR AND

THRUST

WASHER

FIGURE

84.

DISTRIBUTOR

SHAFT

END

PLAY

4.

Set centrifugal advance weights into place and install cam. Be sure the pivots on cam fit into hole in each weight.

5.

Secure cam with spring clip and install weight

springs.

6.

Install and secure breaker plate.

7.

Mount breaker arms on their pivots and place con-

trol-spring end between end

of

the terminal stud and the square metal washer. Then tighten primary terminals.

8.

Align contacts

so

they make contact near the center.

To

do this, bend stationary contact bracket, not the

breaker arm.

9. After aligning the points, check tension of breaker spring with a spring scale hooked on the arm at the contact and held at right angles to contact surfaces (Figure

62).

Tension should

be

17

to

20

02.

If

not,

adjust it by loosening screw holding end

of

contact spn'ng and installing spacing washers or by sliding end

of

the spring in or out.

10.

Rotate

drive shaft

to

obtain

maximum

breaker

point

gap

and

set

gap

for

.020

in.

(Figure

61).

over the spark

plug

hole and ro&e flywheel clockwise

until cylinder builds up pressure. Continue rotating un-

til TC mark on flywheel aligns with timing pointer.

2.

With points in the "Breaking Open" position, push distributor into its mounting hole.

It

may be necessary to rotate distributor slightly to position and mesh distributor and camshaft gears.

3.

Install distributor clamp screw.

4.

Connect coil leads to breaker box cover adapter. See

5.

Connect primary leads to distributor terminals.

6.

Time ignition system.

Figure

60.

MJC

Ignition

Coils

The MJC engine uses

two

suppressed ignition coils mounted on the intake manifold. Normal ignition coil maintenance should include inspecting, tightening, and

cleaning terminals, if necessary.

A

quick check for possible coil failure can be made by simply disconnecting the high tension spark plug leads (cyl.

1

or 4 for coil nearest cyl.

1

-

cyl. 2 or 3 for other

coil).

See

Figure

60.

Then hold end of the leads

1

/4

inch

'from bare engine metal and crank engine.

A

spark

be-

tween lead end and engine indicates coil

is

operating,

although

it

(one coil or the other) may

be

weak, which

could

be

checked only on a tester or by checking re-

sistance.

No

spark indicates that

coil,

points, or control circuit to the coil is defective. Before discarding the coil, if

there is

no

spark, check hi-tension lead for voltage

while cranking engine and inspect breaker points.

POINT

SET

NO.

2

(FIRES

CYLINDERS

2AND3)

52

..

r

MJC

Ignition

Condensers

Two condensers are mounted

in

a vertical position inside

the distributor.

If

they

are

suspected

of

being

defective,

test

and

replace

if

necessary. Capacitance should

be

0.3

mfd.

SPARK

PLUGS

MJB

and

MJC

engines use aviation spark plugs equipped to accept suppressed ignition leads. Fouled spark plugs indicate that they are too cold. Consult engine parts catalog for the factory recommended plug. Remove and inspect plugs at regular intervals.

Replace spark plugs when electrodes become exces-

sively worn or if the plugs are damaged. When replacing or reinstalling spark plugs, always install

new gaskets.

53

Oil

System

J-Series engines have pressure lubrication to all working parts of the engine. Oil system includes an

oil

intake cup, gear-type oil pump, bypass valve, oil pressure gauge, full-flow

oil

filter, and crankcase passages and drillings to deliver oil throughout engine. Oil is held in the oil base, drawn by oil pump, and delivered through the oil filter.

Oil

lines lead to rocker housing, with drillings through the

crankcase

to

crankshaft bearings and camshaft front bearing; crankshaft passages to connecting rod bearings and connecting rod passages to piston pin bushings complete the oil system. The crankcase breather in this system aids oil consumption control, Figure

66.

Normal

oil

pressure should be

25

psi

or

higher when

engine

is

at operating temperature. If pressure drops be-

low

20

psi at governed speed, inspect

oil

system for

faulty components.

CRANKCASE

BREATHER

l

BY-PAS

VALVE-

MAINTENANCE

Periodic oil system maintenance should include changing crankcase oil, cleaning crankcase breather, cleaning rocker box oil lines, and replacing oil filter.

Hot

crankcase

oil

can cause burns

if

it

is

spi/led

or splashed on skin.

Keep

fingers and hands clear when removing the

oil

drain

p/ug and wear protective clothing.

WARNING

OIL PRESSURE GAUGE

The gauge is located on lower front comer of cylinder

block. If it is damaged, replace it. Before replacing, check for

a

clogged oil passage behind the gauge.

naURE

68.

ENQINE PRESSURE

LUBRICATION

SYSTEM

54

OIL

PUMP

Oil

pump is mounted on front of crankcase behind gear

cover and

is

driven by

the

crankshaft

gear.

.

Removal

1.

Remove gear cover and oil base (refer to

Enghe

Re-

pair

section). Unscrew intake cup from the pump.

2.

Remove crankshaft lock ring and gear retaining

washer.

3.

Loosen the two capscrews holding pump to the crankcase, and remove pump.

Repair Except for gaskets, component parts of the pump are

not individually available. If pump is defective or worn, replace

it.

Disassemble pump by removing the

two

cap screws holding pump cover to the body. Inspect for excessive wear in gears and shafts.

To

improve pump performance, adjust gear end clearance by using thinnest gasket that permits free movement

of

pump shaft. Oil

all parts when assembling the pump.

Installation

Before installing, fill pump intake and outlet with oil. Mount pump on engine and adjust for .005-inch lash between pump gear and crankshaft gear. Mount intake

cup on

the

pump

so

it

is parallel with the bottom

of

crankcase.

BY-PASS VALVE

The by-pass valve (located on outside of rear bearing

plate) controls oil pressure by allowing excess oil

to

flow

directly back to the crankcase. Normally valve begins to

open at about

25

psi.

It

is non-adjustable and normally

needs no maintenance.

To

determine if abnormal (high or low) oil pressure is caused by a sticking plunger, clean and inspect valve.

To

remove valve, unscrew the recessed plug in rear bear-

ing plate and

lift

out spring and plunger assembly (Figure

67).

Determine proper valve operation by checking spring

and plunger according to the following measurements. Plunger Diameter

. . . . . .

.

. .

.3365

to

3380

inch

Free Length

. . . . . .

.

2-5/16

inches - 1/16

inch

spting

FIGURE

67.

BY-PASS VALVE

OIL

FILTER

The full-flow filter is mounted on filter plate at

left

front

comer of crankcase. Replace normally after every

200

hours

of operation. Remove filter by turning counter-

clockwise. Lubricate gasket on new filter with engine’oil.

Install filter until the gasket touches base and tighten

1/

2

turn; do not overtighten.

OIL

LINES

Rocker box oil line (Figure

68),

should be flushed with

solvent and small holes cleaned with fine wire at regular

intervals. Clean other oil lines and drillings with

corn-

pressed air whenever engine is disassembled or overhauled. Remove oil mounting plate to reach the oil gauge passage.

FLUSH

ROCKER

BOX

OIL LINE

WITH

FUEL

AND

CLEAN HOLES

WITH

FINE

WIRE.

FIQURE

68.

CLEANING

ROCKER

BOX

OIL

LINE

55

Ti

All external oil lines, rocker box oil line, and internal oil line to rear bearing are replaceable.

CRANKCASE

BREATHER

This breather maintains a partial vacuum in crankcase during operation,

to

control oil

loss

and ventilation.

It

includes a metal filter packed into tube on crankcase, a rubber cap, and a hose connecting it to engine air horn (Figure

69).

To

disassemble, remove breather cap from breather

tube. At the same time, pull baffle out

of

breather tube

and clean it.

BREATHER TUBE

CAP

UBE BAFFLE

FIGURE

89.

CRANKCASE

BREATHER

56

Starting

System

Most engine installations use a starting motor, as shown

in Figure

70.

Starting motor mounts on right side of engine and drives flywheel for starting. It is a standard automotive starting motor with solenoid shift and overrunning clutch, controlled by a start solenoid in control box. When control box solenoid energizes, solenoid on motor operates, shifting starter pinion to engage flywheel ring gear and closing circuit to starting motor. Starting motor remains engaged until after engine starts when control circuit centrifugal switch closes, completing starting cycle. Over-running clutch protects starter armature from overspeeds.

ONAN

doer

not

stock

all

parts

lor

the

starting

motor.

See

an

au-

thorized

dealer.

MAINTENANCE

Check battery water level and charge condition about every

100

hours. Every

500

hours inspect

all

starting system wiring for loose or dirty connections, especially connections to battery terminak.

Separate

Starting

Motor

Every

500

hours check for loose or dirty connections. Check battery water level and charge condition every 100

hours. Inspect starter commutator and, if

it

is dirty,

I

clean with

#00

sandpaper.

Do

not use emery paper or cloth! Check brushes for excessive wear and poor seating on armature.

TESTING

Poor cranking performance can

be

caused by a faulty starting motor, defective battery, or high resistance in starting circuit.

Battery

Check battery condition with a hydrometer. Specific gravity

should

be between

1.260

and

1.225.

If

not, re

charge battery. If battery will not recharge, replace

it.

Wiring

With starting motor operating, check voltage drops

(1)

from battery ground terminal post (not the cable clamp) to cylinder block

(2)

from cylinder block to starting motor

frame and

(3)

from battery positive post to battery ter-

minal stud on solenoid. Each drop should

be

less than

0.2

volts.

If

extra long battery cables are

used,

slightly

higher voltage drops may result. Thoroughly clean

all

connections in any part of circuit showing excessively high voltage drops.

STARTING MOTOR

GROUND CONNECTION

IR

TOENGINE

START

SWITCH

BATTERY

058

FIQURE

70.

Sl'ARl'lNa

SYSTEM

57

f7

_-

VARIABLE

RESISTANCE

L-

I2"-4

FIGURE

71.

TESTING

FOR

TORQUE

Starting

Motor

If starting motor tests are required, remove motor from engine. Complete starting motor tests should include both tests of free-running voltage, speed and current, and also tests

of

stall torque, voltage, and current.

To

test the free-running characteristics, connect starting

motor in series with a battery and ammeter, and install

a tachometer

on

motor. Read free-running current and

speed.

The torque test (Figure

71)

requires a spring scale and

torque arm, voltmeter, ammeter, and variable resistance

to apply voltage specified by test characteristics. The voltage drop across solenoid on starting motor should be less than

1.50

volts.

If

not, remove

it

for repair.

BATTERY

Engines with a separate cranking motor normally use a single

12

volt battery of at least

62

amp.-hour capacity.

The battery charging system maintains batteries at or near full charge at all times. Inspect battery charging system and adjust the charge rate if batteries appear to

be

continually discharged.

Addlng

rccouorks

that

draw

bmrry

current

requires

an

adjust-

nmrtdchrrgrmm.

If discharge or failure to charge cannot be traced to battery charging system, thoroughly inspect and test battery, and replace it

as

necessary.

Armature

Inspect armature for mechanical defects before checking

for grounds or shorted coils.

To test for grounds, use a

12

volt test lamp and check between each segment of commutator and shaft. Do not touch probes to

the

commutator brush surfaces,

as

this

will bum smooth surfaces.

A

growler is necessary to test for shorted coils. With armature in growler, run a steel strip over armature surfaces. If a coil is shorted, steel strip

will

become magnetized and vibrate. Rotate armature slightly and repeat test. Do this for one complete revolution of armature. If armature has a

short

or ground, replace

it.

If

commutator

is

only dirty or discolored, clean it with 00

or

000

sandpaper.

Blow

sand out of the motor after

cleaning.

If,

however, it is scored, rough or worn, turn

it

down in a lathe.

Field

Coils

Using a test lamp and probes, check field

coils

for

grounding to motor frame

or

open circuit. Inspect all con-

nections to be sure

they

are properly clinched

and

sol-

dered. Inspect the insulation for evidences of damage. The only way to check for field coil shorts is to use the starting motor test.

Be

a

ri

n

g

s

If

either front or rear bearings show excessive wear, replace them. Drive old bearings out, and using an arbor press and proper arbor, press new bearings into place.

Brushes

Check brushes for wear

or

improper seating. They

should

slide

freely

in their

hokiers.

Check

brush

spting

tension

with

a

spring

scale.

To

change

spring tension,

twist

spring

at

holder

with long nosed

pliers.

6

58

8

Replace Prestolite brushes when excessively worn, or

when worn to

518

inch in length. Replace Mitsubishi

brushes when excessively worn or when worn to

3/8

inch

in

length.

Brushes

are

soldered to the field coil.

To

remove Prestolite brushes, unsolder the lead and open

the loop in field coil lead. Insert new brush pigtail com-

pletely into the loop and clinch before resoldering.

A

good soldering job is necessary to ensure good contact and low voltage drop across connection.

Over-running Clutch

Clean clutch thoroughly but do not dip in solvent.

It

can-

not be repacked with grease.

GEAR

HOUSING

-

It

should slide easily on armature shaft with no binding.

Turn

the pinion.

It

should rotate smoothly, but not nec-

essarily freely. Reverse direction a few times and it should instantly

lock

and

unlock.

Replace

the clutch

if

operation is defective or pinion is

worn

or damaged.

Shifting Solenoid

See

that plunger moves freely in the coil. Check pull-in

coil continuity between solenoid control terminal and

so-

lenoid connection to motor. Check hold-in coil continuity between solenoid control terminal and ground on the motor.

-

FIELO

COIL

SHIFTING

1

SOLENOID

SOLENOID PLUNGER

FIGURE

73.

PRESTOLITE STARTER

Before installing, check pinion clearance. Proper clearance is important to ensure starter engagement.

PRESTOLITE STARTER REMOVAL

AND

DISASSEMBLY

1.

Remove electrical connections

to

control and battery

.

PreSS-On solenoid Core

t0

shift pinion into full mesh, and

at the shifting solenoid, Figure 73.

measure clearance between pinion and pinion stop, Figure

74.

This should

be

between 0.07-inch and 0.12-inch

starting motor

off

engine. Be careful not to lose any

shims that might be behind the flange.

shift

lever

to

the

solenoid

plunger and remove shift lever pivot pin.

On

engines built before May

1962,

it was necessary to maintain

gap between ring gear and

starter

pinion in relaxed position

at

less

than l/B-inch to enaure

starter

engagement. When installing these

motors, check

this

gap. If it is too great, a shim kit is available to

reduce it

(Figure

75).

3-

Remove

link

4.

Remove thru bolts from the commutator end of motor. Pull

off

end cover and

lift

brushes

off

their seats.

Pull

cast housing from4he front end

of

motor and

lift

ar-

mature and clutch out of motor frame.

-

’

5.

To

remove over-running clutch from armature, drive the retainer away from the ringlock near front end of shaft, remove ringlock and pull the assembly

off.

Do

not attempt

to

disassemble clutch assembly.

6.

If necessary to service the solenoid, remove four capscrews and electrical connection holding it to motor

frame.

To

reach the switch contacts, remove two

screws on rear of the solenoid.

31

STARTING

MOTOF

AND FLANGE

7. Mount starter motor to engine by a direct reversal of the removal procedure. Connect battery cable and wires to starter.

SHIMS

1

8.

Connect battery cables to battery. Connect ground cable last.

PRESTOLITE STARTER ASSEMBLY

Before assembling, soak bronze bearings in oil. They are absorbent bearings, designed to hold up to 25 percent of their own weight in oil. Be sure felt oil pad is in outer end of commutator end bearing.

When motor is assembled, check armature end play.

It

should

be

between 0.005-inch

(0.127

mm)

and

0.030-

inch (0.762

mm).

Adjust end play by adding or removing

washers

on

commutator end of

the

armature.

Required

on

some

early

models.

Be

sure

to

install

same

number

of

shims removed.

FIGURE

75.

STARTING

MMOR

MOUNTING

SHIMS

MlTSUBlSHl STARTER REMOVAL

AND

INSTALLATION

1.

Remove both battery cables from battery. Disconnect

ground cable first.

2. Disconnect battery cable and electrical

lead

wires from

starter.

3.

Remove capscrews and flat washers that attach starter

to

mounting bracket.

4.

Remove starter.

5.

Mount starter motor to engine by a direct reversal of

the

removal

procedure.

Connect

battery

cable

and

wires

to starter.

6.

Connect battery

cables

to battery. Connect ground

cable

last.

(1.78

-

3.05

mm

CLEARANCE)

SEE

TEXT

WRE

74.

CHECKlNG

PINION

CLEARANCE

60

MlTSUBlSHl STARTER DISASSEMBLY

1.

Remove

“M”

terminal

nut

and wire lead from solenoid.

2.

Remove two solenoid mounting screws, and remove solenoid.

3.

Remove

two

through bolts and brush holder retaining

screws. Remove rear bracket (Figure

76).

THROUGH

BOLTS

REAR

BRACKET

W

ES-1186

FIGURE

76.

REMOVING REAR

BRACKET

4.

Remove frame assembly, and brush holder assembly, while pulling brushes upward. Then remove armature assembly.

5.

Remove cover assembly (snap ring and washer) from the pinion shaft (Figure

77).

COVER

ES-1195

SNAP

RING

6.

Remove capscrew that secures center bracket to front bracket. Remove center bracket; several washers

used

to adjust pinion shaft end play can now

be

re-

moved (Figure

78).

7.

Remove gear, spring set, and lever assembly from front bracket. Note direction in which lever assembly is installed.

CENTER

ADJUSTMENT

WASHERS

CAPSCREW

ES-1187

FIGURE

78.

REMOVING

CENTER BRACKET

8.

Push pinion gear and stopper down and remove

re-

taining ring. Remove stopper, pinion gear, spring, and pinion shaft assembly.

9.

Inspect ball bearings.

If

they are rough or noisy when

rotated, replace them. Front bearing is

not

replaceable

and must be replaced with bracket.

FWRE

77.

REMOVING

SNAP

RING

AND

WASHER

.

61

SOLENOID

F

FRONT WA

PACKING

BRACKET LEVER

\

\SCREW

STOPPER SPRING

(RETAINING

RING)

/

FRAME

ASSEMBLY

BRUSH

HOLDER

ASSEMBLY

XES-1255

FIGURE

79.

MlTSUBlSHl

STARTER

MlTSUBlSHl STARTER ASSEMBLY

For assembly ~~VerSe disassembly Procedure, but note

following items.

See

Figure

79.

Whenever starter motor is disassembled apply grease to each of following points. (Recommended grade; Multemp

PS

No.

2.)

If pinion gear has not been removed, place pinion shaft and reduction gear between front bracket and center bracket. With lever spring removed and bolt tightened, push pinion shaft out and measure end play. Adjust end play if necessary by adding or removing shims.

Armature shaft gear Reduction gear Ball bearing (Both ends

of

armature)

Stopper on

pinion

shaft

Sleeve bearing Pinion gear Sliding portion of lever

Pinion

Shaft

End

Play

Adjustment

Adjust end play

so

that it is

0.1

to

0.8

mm

(.0039

to

.0315

inch)

with

adjusting washers placed between cen-

ter bracket and reduction gear (Figure

80).

With pinion gear removed, install reduction gear onto

pinion shaft. Place pinion shaft into center bracket and secure with washer and snap ring. Measure end play with a feeler gauge

between

center bracket and gear. If

necessary,

adjust end play

by

adding

or

removing ad-

justing washers.

OVERRUNNING

CLUTCH

PINION

GEAR

PINION SHAFT

\

SNAP RING

/

WASHER

CENTER

ADJUSTING

WASHER

BRACKET

FKUlRE

00.

ADJUSTING

PiNlON

8HAFT

END

PLAY

Pinion Gear Installation

Place spring and pinion gear onto pinion shaft. Slide stop

ring

onto

pinion

shaft,

and install

retaining

ring

in

groove.

Pull

stop

ring over retaining ring (Figure

81).

&

SNAP RING

ES-1194

FIGURE

81.

PINION GEAR INSTALLATION

Lever

Assembly

Installation

Figure

82

shows

correct method of installing the lever

assembly, spring, and packing. Pay close attention to

direction

of

lever.

PACKING

LEVER

II

LEVER

1

SPRING

i

Pinion Gap

Adjustment

After assembling starter motor, adjust pinion gap.

1.

Remove

“M”

terminal

nut

and

wire

from

solenoid.

2.

Connect positive terminal of battery

to

“S”

terminal on solenoid and negative terminal to starter body. With battery connected pinion gear will shift into the cranking position.

PINION

I

AMOllNT

OF

TRAVEL

A

(PINION

GAP)

i

ES-1192

FIGURE

83.

PINION GAP ADJUSTMENT

3.

Gently push pinion shaft back towards front bracket

and measure the amount

of

travel (Figure

83).

4.

The pinion gap should be

0.3

to

2.0

rnm

(0.118

to

.0787

inch). Adjust by changing numberoffiberwashers used on solenoid mounting surface. Increasing number of fiber washers decreases clearance. Decreasing number of washers increases clearance.

ES-1185

FIQURE

82,

LEVER

INSTUTION

63

Engine

Disassembly

This section covers various assemblies and parts of engine.

All

repairs should be done by a competent me-

chanic. Maintain factory limits and clearances (see

Dimensions and Clearances

section).

CYLINDERHEADSANDVALVES

Each cylinder head assembly contains valves, valve seat inserts and guides, rocker arms and spark plugs. Valve assemblies are operated by pushrods running through cylinder head and push rod shields to camshaft. Exhaust valves are hardened chrome alloy-faced and ride on hardened chrome-alloy seat inserts. All valves have releasetype rotators.

Check valve clearances at regular intervals. In addition, scrape combustion chambers clean and inspect the valves and valve seats regularly.

If

combustion chambers show excessive carbon buildup, reduce the interval between cleaning.

Valve

Adjustment

After engine has reached a stable temperature condition, the valve clearances may be adjusted.

It

is recommended

that valve clearance be set with engine at room tem-

perature (approximately

75°F).

Allow at least two hours

cooling time after engine operation.

MJB

Series

Adjust valve clearance on the

MJB

engine as follows,

obtaining valve clearances from

Specifications

section.

1. Turn flywheel

so

piston of valve to be checked is be-

tween 10 degrees and 45 degrees after TDC (about

2

inches after TDC) of the compression stroke.

2.

Turn flywheel until the TC (top center) mark on flywheel lines

UD

with timina oointer on aear cover. Then

3.

4.

turn flywheel'in a clockv&e direction"for

an

additional

10

to 45 degrees. There is no timing mark for this

position

so

it must be estimated. With piston located in this position the cylinder will be in its power stroke with both valves completely closed.

Check cylinder head-bolt torque. Using a feeler gauge, check the clearance between

the rocker arm and the valve (see Figure 84). Increase or reduce the clearance until proper gap is established, adjusting with the locknut which secures rocker arm to cylinder head.

MJC,

RJC

Series

Adjust valve clearance on the four cylinder engine as follows:

FIGURE

84.

SETTING VALVE CLEARANCE

1. Adjust valve clearance in the firing order (1-2-4-3) sequence. After the cooling period, set timing for number

1

cylinder and valve clearance.

2.

To adjust valve clearance for number 2 cylinder, turn flywheel in a clockwise direction 180 degrees

(1

/2 revolution) from position used in step 1. The flywheel position should be between 10 degrees and 45 degrees past the BC (bottom center) flywheel mark.

Early

model

four-cylinder engines

do

not have

a

BC

mark

on

flywheel.

3.

After timing number 2 cylinder, adjust valve clearance.

4.

To adjust valve clearance for number 4 cylinder, turn flywheel in a clockwise direction 180 degrees

(1/2

rev-

olution). The flywheel should be between 10 degrees

and 45 degrees past TC flywheel mark.

5.

After timing number 4 cylinder, adjust valve clearance.

6.

To adjust valve clearance for number 3 cylinder, turn flywheel in a clockwise direction 180 degrees

(1

/2

rev-

olution). The flywheel should be between

10

degrees

and 45 degrees past

BC

flywheel mark.

7.

After timing number 3 cylinder, adjust valve clearance.

64

5.

Using a valve spring compressor, disassemble valve

assemblies.

Repair

Thoroughly clean all components of the cylinder assemblies. Remove all carbon deposits from cornbustion chambers and clean all gasket surfaces.

Remove all carbon and check each valve for burning, pitting or warped stem. Valves that are slightly pitted or burned should

be

refinished on

an

accurate valve grinder

to a

45

degree angle.

If

they are badly

pitted,

or

will

have

a thin edge when refaced, replace them. Check refinished valves for a tight seat to the valve seat

with an air pressure-type testing tool or by applying Prussian Blue on valve face and rotating

it

against the seat.

Check valve guide-to-valve clearance. If proper clearances cannot be obtained by replacing valves, replace the valve guides. Drive old valve guides in until they protrude 11132-inch from the rocker box side of the head.

FIGURE

85.

VALVE

MECHANISM

Compression

Test

Compression

of

a standard new engine cranking at about

uniform, normally with less than

10

psi differences

be-

tween the highest and lowest cylinder, taken at the same

cranking

Wm.

Ex@ssiveb high readings indicate car-

boned combustion chambers.

Compression readings will change because of differences in cranking speed, altitude and ambient temperature conditions. Compression limits are given only as a

'

guide. The best indication of leakage is the pressure difference between cylinders or a compression increase when oil is added to the cylinder.

Disassembly

before

it

becomes

them,

Use valve seal remover in a

drill

press (Figure 86)

to

remove each valve seat. Adjust the tool to cut 1/64-inch from the edge of seat.

-

to

replace

it*

300

rpm

is

about

lo

Psi.

be

If

valve seats are loose or cannot

be

refaced, replace

VahrM,

trppra,

rockrr

ann8

and

pushrods

should

be

kept

In

order

and

returned

In

saw

ordor.

1. Remove rocker

box

cover,

spark

plugs and connecting

oil

lines

to

cylinder heads. Remove intake and exhaust

manifold.

inder

Mock,

soft

hammer.

Do

not use a

pry.

-

--

2.

Remove

capscrews holding each cylinder head

to

cyl-

--

-

FWRE

1.

REMOViNa

VALVE

8EATS

3.

Remove each head. If

it

sticks,

cap

it

sharply with a

Oil

Dilot

to

Drevent seizina

in

the valve auide. Cut each

4.

Remove rocker

arms

and pushrods.

se&

down

'to

a

narrow

&d

on

edges

&d

bottom

and

break

it

out

with a sharp tool.

Be

careful

not

to cut into

the

counterbore

bottom.

Thoroughly clean valve seat counterbore and remove any burrs from edges.

If

counterbore is damaged, machine

for oversize seat. Oversize seats are available in

.002

inch,

.005

inch,

.010

inch and .025 inch. Otherwise, install

new standard-size seat inserts. Drive new valve seat inserts into place. Each seat must

rest solidly on bottom of the counterbore at all points. To ease installation, heat cylinder head in an oven at 325°F for about 1/2 hour and cool valve seats in

dry

ice.

After installation, and before facing new seats, peen the head material against the valve seat in three areas between the machine roll marks (Figure

87).

CROWD

METAL

OF

HEAD

AGAINST VALVE SEATS

BY

PEEN I NG

AREA

BE-

MACHINE

ROLL

\?\.AS\W!-~PEENED

AREA

FIGURE

87.

PEENING VALVE SEAT AREA

Face each new seat

to

a

45

degree angle and width

of

approximately 3/64-inch. Finished seat face should contact the approximate center of valve face. Use Prussian

Blue on each valve face to check this. Make corrections

to seat, not the valve face. Check valve springs on an accurate compression scale.

Replace any spring that is weak, cracked or pitted, or

has ends out of square. See

Dimensions and Clearances

section for valve spring data.

Installation

1.

Push a new valve stem oil seal onto each intake valve guide and clamp in place. Then oil the inside surface of each seal.

2. Oil stem of each valve lightly and insert each in its own guide.

3. Check each valve for a tight seat with an air pressure type-tester. If a tester

is

not available, make pencil marks at intervals on valve face and observe if marks rub

off

uniformly when valve is rotated part of a turn

in seat.

If

the seat is not tight, regrind valves.

4.

Using a valve spring compressor, compress each valve spring with its spring retainer in place and insert retainer locks.

Spring retainer should never contact valve stem seal when compressing valve springs.

5.

Coat both sides of heat gasket with Permatex

No.

3

(pliable sealer). Install head assembly and gasket

to cylinder block. Tighten head bolts

1

or 2 turns.

6. Make up pushrod shield assemblies by installing an O-ring (Figure

88)

on one end of rod and a spring,

washer and O-ring

on

opposite end. Lift cylinder

heads and install pushrod shield assemblies.

BEFORE TlGHTE N I NG CYLINDER HEAD BOLTS LIFT HEAD SLIGHTLY WHILE DEPRESSING

VALVE

PUSH ROD SHIELD

AND

SPRING.

INSERT UPPER END OF SHIELD

INTO

HOLE

PRO-

VIDED

IN

HEAD.

,

FIGURE

88.

INSTALLING PUSH

ROD

SHIELDS

66

0

7,

8.

9.

10.

Tighten head bolts to

44

to

46

Ibs.

ft.

following the

sequence in Figure 89.

Four

cylinder

models;

observe

the

following

special procedure

to align

the

two

heads

and

prevent air leaks.

a. Assemble heads, gaskets and pushrod shields to

block and install capscrews, but do not tighten.

b. Install intake manifold to heads and tighten nuts c. Tighten cylinder head capscrews, following se-

Install exhaust manifold, oil lines, spark plugs and carburetor. Install valve stem caps. Install pushrods, rocker arms and rocker arm nuts.

Set valve clearance.

to

13-15

Ibs.

ft.

.

quence in Figure 89.

After

the first

50

hours

of

operation, retighten the cylinder head

bolts

and check valve clearance.

Reinstall rocker box cover.

FIGURE

89.

CYLINDER

HEAD

BOLT

TORQUE SEQUENCE

PISTONS, CONNECTING RODS, CYLINDERS

Each cam-ground aluminum piston

is

tapered and fitted

with

two

compression rings and an oil control ring. Full

floating piston pins held

in

place with snap rings connect piston to its connecting rod. Lower end of each connecting rod contains half shell, precision bearings and upper end, semi-finished bushings.

EIIQIMS

mrlud

wlth

an

E

folkwing

qhn

mtal

nwnkr

an

filtmd

uloso

phtons.

wtth

.OW.krchOwaiZOpkton8

am.

UWrSlndrrd

fhQ8

for

Removal

and

Disassembly

Connecting rods and caps are stamped with numbers for installation in proper cylinder. When removing piston assemblies, check marking

so

each

can

be

reinstalled in

the

proper cylinder. Keep

all

components

of

each piston

assembly together.

1

I

Drain crankcase

oil

and remove

oil

base, air housing,

2.

Scrape

off

carbon ring at

top

of

each cylinder

to

pre-

and cylinder heads.

vent damaging rings or pistons.

3.

Remove connecting rod cap and push assembly through the top of cylinder bore. If ridge at the top of cylinder interferes with piston removal, cut it down

with

a

ridge remover before taking piston assembly

out.

4.

Using a ring expander, remove rings from each piston.

5.

Remove the two retaining rings and push piston pin

from each piston.

Cylinders Cylinder walls should be free of scratches, pitting, and

evidence of wear. Check with an inside-reading micrometer for excessive out-of-round or taper. New cylinder dimensions are 3.2495 to 3.2505 inch.

If necessary, rebore cylinder to fit the next oversize piston. Pistons and ring sets are available in

.010

inch,

.020

inch and

.030

inch oversize. If refinishing is not required,

remove any ridges from top

of

the wall with a ridge cutter,

or if ridge is small, a de-glazing stone.

Pistons

Clean carbon from ring grooves and make sure

all

oil

holes are open. If any piston is badly scored

or

burred,

loose in the cylinders, has badly

worn

ring grooves or

shows excessive wear, replace it.

Check clearance by inserting each piston in its cylinder. Check the clearance

90

degrees from the axis of the

piston pin and 3/8-inch below the oil control ring. Clear-

ance should be

.0012

inch

to

.0032

inch. If

it

exceeds

the limits, replace piston and check cylinder bore size.

Piston Pins Each pin should

be

a thumb push fit into its piston at

room temperatures.

If

pin is excessively

loose,

install a

new pin or the next oversize pin.

If

piston is

worn

so

that

oversize pin will not fit, replace piston.

Rings

Inspect each ring carefully for fit in piston grooves (Figure

90)

and for seating

on

cylinder wall. Fit each

ring

to

cyl-

inder wall

at

the bottom of its travel, using a piston to

square ring in the

bore.

Check end

gap

with a feeler

gauge, Figure

91.

It

should

be

.010

inch

to

.020

inch.

If

.gap

is

too small,

file

the

butt

ends of the rings.

Do

not

67

use rings that need a lot of filing, as they won’t seat properly on cylinder walls. If oversize pistons are used, use the correct oversize rings.

During piston ring replacement de-glaze cylinder walls with either a de-glazing hone or emery paper.

Do

not

change diameter of cylinder bore.

HEAVIEST COMPRESSION

RING IN TOP GROOVE

COMPRESSION RINGS

OIL CONTROL RING

-

*

RAI

LS

ARE

NOT

USED

ON TWO CYLINDER ENGINES

FIGURE

90.

PISTON

RINGS

ISTON RING

IN

YLINDER BORE

FIGURE

91.

CHECKING PISTON RING

END

GAP

Create a cross hatch pattern on cylinder walls. After deglazing, be sure to completely clean cylinder walls and

the rest of engine to remove all residue.

Connecting

Rods

Clean each connecting rod .and check for defects. Check upper connecting rod bushings for proper piston pin clearance. Clearance should be

.0002

inch to

.0007

inch.

Press out excessively worn bushings and install new bushings. Press new bushings in until they afe centered in connecting rod (Figure

92).

After installation, drill the bushings with a 3/16-inch drill through the counterbored hole in connecting rod top. Be sure connecting rod oil spray hole is open.

A752

3/16

”

DRILL

IS

TO BE

THROUGH BUSHING

AFTER ASSEMBLY

IN

ROO.

BUT BEFORE

BUSHING

IS

FINISHED

REAMED

BUSHING

TO BE

ASSEMBLED WITH

SPLIT IN THIS

CROSS-SECTION

ZONE

PRECISION TYPE

BEARING

MEASURE CLEARANCE IN

DIRECTION INDICATED

BY ARROW

FIGURE

92.

CONNECTING

ROD

BUSHINGS

Connecting

Rod

Bearings

Inspect connecting rod bearings for burrs, breaks, pitts and wear. Measure clearance between bearings and crankshaft journal. Clearance should be

.001

inch to ,003

inch. If necessary, replace with new standard or oversize

precision bearings. Refer to Dimensions and Clearances section for journal size.

1.

Install connecting rods

on

each piston with pins and

retaining pins. Install

so

connecting rod oil spray hole

is on the same side as the

V

notch in each piston.

2.

Install all rings on each piston. Tapered-type rings are marked TOP or identified

in

some other manner. Place this mark toward the closed end of piston. Space ring gaps 1/3 of the way around piston from one another. No gap should be in line with piston pin. Oil rings and pistons.

3. Position a bearing half in each connecting rod. Be sure there

is

no dirt under bearing. This could cause high

spots and early bearing failure.

4.

Oil cylinder walls and pistons. Install each piston in

proper cylinder using a suitable installer. Each assembly should

be

installed with V mark on piston toward

front of engine. The word “Front” may be found on

some piston tops. See Figure 93.

V

68

L

FIGURE

93.

PISTON TOP IDENTIFICATION

5.

Position each connecting rod on crankshaft, oil the

journal and install its rod cap with bearing half. When

installing rod cap, position

so

raised witness mark on

the forging matches mark on connecting rod (Figure

94).

6.

Tighten connecting rod capscrews to specified torque

(27-29

ft.-lb.).

l,llllllllllllll1l11111

CRANKSHAFT

FIGURE

94.

CONNECTING ROD WITNESS MARKS

7.

Crank engine over

by

hand to see that all bearings are

8.

Install oil base with a new gasket. Install cylinder

free.

L

heads.

Break-in

Period

Whenever new rings or pistons are installed, or the cylinder refinished, the engine must

be

run-in before regular

operation. Run the engine for

15

to

20

minutes at no

load, about

1/2

hour at

1/3

load and 2 to 3 hours at

2/3

load. Then resume regular operation.

Avoid light loads during balance of the break-in period to best seat rings

for

oil control.

ENGINE

DISASSEMBLY

During engine disassembly, observe the following order (i.e., Flywheel, Gear Cover, etc.). As disassembly pro-

gresses, the order may be changed somewhat

as

will

be

self-evident.

Engine assembly procedure is the reverse of disassembly. Any special assembly instructions for a particular component are included. When reassembling, check for special assembly instructions or procedures.

Flywheel

The flywheel is a tapered fit on the crankshaft. Flywheel

is removed by using crank dog as a puller as follows: first remove crank dog and flywheel mounting capscrew. Then remove larger washer from flywheel mounting capscrew and reinstall the screw part way. Install the washer into crank dog and mount crank dog

so

the washer bears

against the end

of

flywheel mounting screw. Tighten two

crank dog capscrews alternately until flywheel comes

loose. See Figure

95.

_.Z

..

A762

TIGHTEN

CRANKDOG MOUNTING

SCREWS

ALTERNATELY

UNTIL

.FLYWHEEL

IS

1

LOOSENED

FIGURE

95.

PULLING

FLYWHEEL

Ring

Gear

Remove ring gear

by

sawing part way through, then

break

it,

using a cold chisel and heavy hammer.

69

I

!

-i

To

install a new ring gear, place

it

in an oven heated to

380-400

degrees for

30

to

40

minutes. When heated

properly, the ring will fall into place on flywheel. If

it

binds,

drive it into place with a hammer.

Do

it

fast and do not damage gear teeth. Ring will contract rapidly and may shrink to flywheel before it is in place.

If

this occurs,

a

new ring gear may be required.

Gear Cover

To

remove gear cover, detach upper governor ball joint and remove the ignition breaker points (Start-Disconnect switch), plate and gear. Remove screws holding gear

cover to the crankcase. To loosen gear cover, tap

it

with

a soft hammer.

Governor Shaft

Two sets

of

needle bearings support the governor shaft.

To

remove shaft from gear cover, remove governor yoke

and pull the shaft from gear cover. If shaft binds during

operation, clean the bearings. If loose, replace bearings.

To

remove larger bearing, drive both bearing and oil seal out from the outside of gear cover. Remove smaller bearing with an Easy-Out

or

similar tool. Press new bearings

and

oil

seal into place.

BE SURE THAT OIL

PASSAGES

ARE OPEN

INSTALL OIL SEAL

FLUSH WITH THIS

SURFACE

THIS SURFACE MUST

BE CLEAN BEFORE

INSTALLING SEAL

-

FIGURE

96.

GEAR COVER OIL SEAL

Gear Cover

Oil

Seal

Replace oil seal if damaged or worn. Drive old seal out from inside gear cover. Lay cover on a board

so

the seal boss is supported. Using an oil seal driver, insert new seal from the inside with rubber lip toward outside

of

gear cover (open side

of

seal inward) and drive it flush

with the outside surface (Figure

96).

During gear cover installation, reverse the driver to protect oil seal. Lubricate lips with heavy grease.

GOVERNOR ARM

GOVERNOR SHAFT

Y

(SMOOTH SIDE

TOWARD CUP)

VERNOR CUP

GOVERNOR CUP

STOP PIN----

”FITS INTO

GOVERNOR

IF

FEELER

WILL

ENTER HOLE

112’’

BALL HAS FALLEN

(Late models have

larger

ball

which

will

not

fall out)

OUT.

I

FIGURE

97.

GEAR

COVER

ASSEMBLY

70

1.

Operate governor shaft to check for binding and see that

governor

shaft end thrust ball

is

in

place (Figure

2.

Turn governor yoke

so

smooth side is toward governor

cup. Set governor cup

so

stop pin in gear cover will

fit

into one of holes in cup surface. Measure distance

from end

of

stop pin to mounting face of cover.

It

should be 25/32-inch. If not, replace pin. Position open edge of pin toward crankshaft seal to avoid governor cup drag.

97).

Use an oil seal driver (or a piece of shim stock over crankshaft keyway) to protect oil seal and install gear cover. Tighten mounting screws to specified torque. Before tightening screws, be sure stop pin is in governor cup hole (Figure

97).

Install and time ignition points on

MJB

engine (see

1gnifion

System).

Install and gap centrifugal switch on

MJC

and

RJC.

WHEN GOVERNOR

IS

PROPERLY ASSEMBLED THE DlMENSl ON DRAWING

CENTER PIN

GOVERNOR CUP

GOVERNOR FLY BAL

FIGURE

98.

GOVERNOR

CUP

Governor

Cup

To remove governor cup, remove snap ring from cam-

shaft center pin and slide the cup

off.

Catch the

10

fly-

balls that will fall out when cup is removed. Replace any

flyballs with flat spots or grooves. Replace cup

if

the race surface is grooved or rough. Governor cup must be a free spinning fit on camshaft center pin, but should be replaced if excessively loose or wobbly. See Figure

98.

The center pin must extend

25/32

inch from camshaft

gear to give

the

proper travel distance from the cup. If

less, engine may race; if more, the cup

will

not hold the

balls properly. If distance is too great, drive or press

,enter pin in. If it is too small, replace the pin.

It

cannot

e

removed without damaging the surface. In some ,ases, if distance is too small, head of the governor cup can

be

ground to give the necessary 7/32-inch travel

distance.

To

install governor assembly,

tip

the front of engine upward. Set flyballs in their recesses and position governor cup on its shaft. Install snap ring on the center pin.

Camshaft

The camshaft is a one piece machined casting, driven through gears by the crankshaft. It rides on sleeve bear-

ings pressed into crankcase. In addition to opening and closing valves, the camshaft

operates the fuel pump and, on

MJC/RJC

engines, the

distributor.

Remove camshaft as follows:

1.

Remove rocker arms and pushrods from valve

chambers.

2. Remove fuel pump from the engine. Remove distributor

(MJC/RJC

engines only).

3. Remove crankshaft gear retaining washer by removing lock ring on crankshaft.

4.

Lay engine on its side to avoid dropping tappets and remove camshaft assembly as

a

group. If necessary,

pry

it

out with a screwdriver between camshaft gear

and crankcase.

Be

sure

camshaft

lobes

do

not

catch

on

pushrod

tappets

during

removal.

5.

Remove tappets from camshaft end of pushrod holes.

If a lobe is slightly scored, dress

it

smooth with a fine

stone.

If

camshaft is badly worn or scored, replace

it.

The camshaft gear is a press fit on camshaft and drives

it

at one half crankshaft speed. The gear drives the ignition timing (startdisconnect switch on four cylinder) gear on

two

cylinder models. To remove, use a hollow tool or pipe that will fit inside the gear bore and over the center pin. Press camshaft out of gear bore. Be careful not to damage center pin.

The camshaft bearings should be replaced if the clearance to the camshaft is greater than specified; or if bearings show cracks, breaks, burrs, excessive wear or other defects.

The camshaft

to

bearing clearance should be .0012 inch

to

.0049

inch.

To

check rear bearing, remove expansion

plug at rear of the crankcase. Press new bearings into place (Figure

99)

using bearing driving tool. Press rear bearing flush with the bottom of expansion plug recess. Press front bearing in flush with the crankcase front surface

so

crankcase and bearing oil passages align. After rear bearing is installed, insert a new expansion plug in the recess, using sealing com-

pound,

and

expand

it

into place with sharp blows at its center. The bearings are a precision-type and do not require reaming. Install camshaft assembly as follows:

71

PRESS BEARING

FLUSH

WITH

BOTTOM

OF

RECESS

REAR

BEARING

31

+L

95%

I6

FIGURE

99.

CAMSHAFT BEARINGS

1.

Install key and press camshaft gear on its shaft, Figure

2. Slide thrust washer onto shaft.

3.

Lay engine on side

or

end and insert pushrod tappets.

4.

Install camshaft assembly in engine. Align timing

marks on camshaft gear and crankshaft gear (Figure

5, Replace pushrods and fuel pump. Install and retime

Crankshaft

The engine uses a counterbalanced, ductile crankshaft. The two-cylinder crankshafts ride on two lead-bronze

bearings, the front one housed in the crankcase, and rear one in bearing plate.

100.

Mount governor components.

101).

distributor

(MJC/RJC

only).

MEASURE END PLAY

ANKSHAFT WASHER

.

PRESS BEARING

FLUSH WITH

FRONT CRANK-

CASE SURFACE

ALIGN

OIL

ll

%I--

I

HOLES

Four-cylinder model uses an additional split center main bearing.

Remove crankshaft as follows:

1.

Remove lock ring and retaining washer in front of

crankshaft gear.

2.

Pull

off

crankshaft gear, Figure

102.

It

has two 1h-20

UNC

tapped holes for attaching a gear pulling ring

(ONAN

tool 420-0275). Use care not to damage teeth

if gear is

to

be reused.

3.

Remove oil pan and piston and connecting rod assemblies.

4.

Four

Cylinder Only. Remove bearing cap from center

main bearing.

TIMING

GEARS

I

FIGURE

100.

CAMSHAFT

END

PLAY

FIGURE

101.

TIMING

MARKS

72

FIGURE

102.

REMOVING CRANKSHAFT GEAR

5. Remove rear bearing plate from crankcase. Retain

or

measure thickness of rear bearing plate gaskets. These gaskets determine crankshaft endplay.

6.

Remove crankshaft through rear opening in crankcase.

(Four

Cylinder Only-Catch upper half of main

bearing support as

it

slides off its mounting surface.)

Thoroughly clean and inspect crankshaft and blow out

all oil passages with compressed air. Check all journals for out-of-round, taper, grooving or ridges. Pay particular attention to ridges

or

grooves

on

either side of oil hole

areas which indicate neglect of oil cleanliness.

If

journal dimensions are not within the limits,

or

journals

are scored, machine the crankshaft. Crankshaft machining requires a trained and experienced operator and suitable equipment.

Undersize bearings and connecting rods are available to

rework the shaft to

.010

inch,

.020

inch and

.030

inch

undersize.

If

main bearing clearances are greater than the limits or

if

bearings are worn, grooved, or broken, replace them.

Precision replacement bearing inserts and thrust wash-

ers are available for all main bearings.

Do

not ream pre-

cision type bearings. Refer to Dimensions

and

Clearances

for crankshaft tolerances.

Align oil holes and press new bearings into front and rear

housings. Insert the MJCIRJC center bearing when crankshaft is installed.

See

Figure

103.

Crankshaft rear oil seal is in rear bearing plate. If damaged, drive

it

out from the inside

of

the plate. Using oil

seal installing

tool,

install a new seal with rubber lip facing

outward (open side

of

seal inward). Drive new seal flush with rear surface of bearing plate. Leave seal installer on during bearing plate installation to protect oil seal.

Lu-

bricate lips with heavy (high temperature) grease.

Install crankshaft as follows. After each step, turn crankshaft to be sure it has not seized.

1.

Press front and rear main bearings into place; align bearing and bearing housing oil holes.

Do

not attempt to drive a bearing into a cold block or rear bearing plate. Install thrust washers and locking pins.

2.

Oil bearing surfaces and install crankshaft

from

rear

of crankcase, through rear bearing plate hole.

3. Mount and secure rear bearing plate with same thickness of new gaskets as removed.

4.

Heat crank gear to about 350°F. Install key on crankshaft, then drive gear into place. Install retaining washer and lock ring.

THRUST

WASHER

---

FIGURE

103.

MAIN

BEARING INSTALLATION

73

5.

6.

7.

SIDE MARKED “FRONT”

TOWARD CRANKSHAFT

BEARING HALF

PLACE UPPER BEARING HOUSING

HALF IN POSlTlON INDICATED

BY

CRANKSHAFT BROKEN LINE. ROTATE INTO

POSITION

BEARING HALF CENTER MAIN BEARING

HOUSING (UPPER HALF)

FIGURE

104.

CENTER

MAIN

BEARING

(FOUR

CYLINDER

ONLY)

Four

Cylinder

Only.

Set upper half of center main

housing on crankshaft and rotate

it

into place.

Be

sure

side marked

FRONT

is toward crankshaft gear. Set two positioning dowels on upper bearing mount. Install center main bearing cap and torque bolts to

97-102

Ib.-ft. (Figure

104).

Check crankshaft end play. Use enough rear bearing plate shims and gaskets

to

provide

0.010

inch

(0.254

mm) to

0.015

inch

(0.381

mm) end play.

If

gaskets of more than

0.015

inch

(0.381

mm) total

thickness

is

required, use a steel shim

of

proper thickness and a thin gasket on’each side of shim. This avoids excessive gasket compression and

maintains bolt torque.

2.

Place removal tool in guide and position in arbor press

Do

not use hammer to remove old

guides (or to install the new ones).

3.

Run fine crocus cloth

on

a small polishing rod through

cylinder head valve guide hole to clean

out

carbon and

other foreign materials.

Be careful not to enlarge guide hole

or

excess oil consumption may

result.

using care in pressing old guide out.

Install piston assemblies.

P‘

’

’1

a

Crankcase

On

four cylinder model,

if

center main beairng support requires replacement, the whole crankcase must be replaced

or

returned

to

factory to have a new housing

fitted.

REPLACING

VALVE

GUIDES

Use this procedure for removing and replacing J Series

valve guides in cylinder head.

Removal

1.

Before pressing guide out, use wire brush and

electric drill

to

remove carbon and all other foreign

matter from top surface of guide.

Damage could occur to guide wall

in cylinder head

if

this

procedure

is

not

followed.

REAR BEARING

MEASURE

END

PLAY

(Refer

to

Table

of,

Clearances)

FIGURE

105.

CRANKSHAFT

END

PLAY

74

Installation

Coat outer edge

of

new guide with

oil

(or other

lu-

bricant). Position guide notch up in cylinder head and press in until guide protrudes 11/32-inch

from

the

rocker box side

of

head.

2.

Place valve guide reamer in drill press

(if

not available,

3

L

use an electric drill).

Two

different size reamers are

used:

-

for intake guide, use reamer size 0.342 to 0.343 inch.

-

for exhaust guide, use reamer size 0.344

to

0.345

inch.

3. Use polishing rod and crocus cloth to obtain

a

good

4.

Thoroughly wash cylinder head in solvent after ream-

smooth honed finish after reaming.

ing and honing are completed.

75

E

Curnmins Power Generation 1400 73rd Avenue

N.E.

Minneapolis,

MN

55432

763-574-5000

Fax:

763-574-8087

Cummins and Onan are registered trademarks

of

Cummins inc.