
This Service Manual is Dedicated to --
FIRST - Lawn-Boy Service Accounts everywhere. It
has been designed for your use-primarily.
SECOND - Our Lawn-Boy Retailers. If theywilluse
it, all our jobs will be easier.
THIRD - Our Consumer. Without him this bookwould
not be possible.
The objective of LAWN-BOY, A PRODUCT GROUP OF OUT-
BOARD MARINE CORPORATION GALESBURG, ILLINOIS is
to provide quality lawn and garden equipment to its customers at
as reasonable a price as possible. There will be no compromise on
quality of product, or on SERVICE behind our products.
THE RIGHT WAY IS THE ONLY WAY TO DO ANY-
THING. FAIRNESS AND HONESTY TO EVERYONE
WITH WHOM WE DO BUSINESS IS OUR CREED.
With these as our standards, we (you and Lawn-Boy) will
have continuing success, year after year.
SAFETY
THE PURPOSE OF SAFETY SYMBOLS IS TO ATTRACT
YOUR ATTENTION TO POSSIBLE DANGERS. THE SYM-
BOLS, AND THE EXPLANATIONS WITH THEM, DESERVE
YOUR CAREFUL ATTENTION AND UNDERSTANDING.
SAFETY WARNINGS DO NOT BY THEMSELVES ELIMI-
NATE ANY DANGER; THE INSTRUCTIONS OR WARNINGS
DENT PREVENTION MEASURES.
Symbol Meaning
THEY GIVE ARE NOT SUBSTITUTES FOR PROPER ACCI-
SAFETY FAILURE TO OBEY A SAFETY
WARNING WARNING MAY RESULT IN IN-
JURY TO YOU OR TO OTHERS.
ADVISES YOU O F INFORMATION
OR INSTRUCTIONS VITAL TO THE
OPERATION OR MAINTENANCE OF
YOUR EQUIPMENT.

Over the past 60 years the American consumer has been offered many
kinds of luxuryitems,conveniences,laborsavingdevices,andrecreationand
sports equipment. The ingenuity of the inventor, combined with engineering
and manufacturing know-how, has provided the consumer with many things
he would not even have dreamed before. That’s PROGRESS.
Today, service and repair shops “never had it so good.” Manyof these
luxuries and conveniences are mechanical. They have become necessities. As
a result, the good service repair shop has started to build and expand. And,
the number of shops has increased terrifically in the past few years.
New discoveries are being made every day. Inventions are turned into
foreword
products ready for the. consumer in ever increasing
quantities year after year. So, the service business should
be good for many, many. years to come. And, manufac-
turers are becoming increasingly aware of the consumer
as the “guy who pays for everything.” He is the one they
have t o keep happy.
Quality manufacturers realize that the closest link they
have with the consumer is that which exists through their
service dealers. That’s why many manufacturers, includ-
ing Lawn-Boy, have based their over all service programs
on the service dealer level, planning the entire program
upward from there. Years ago we started our Lawn-Boy
service program by planning the easiest and simplest
methods of service procedure and policy, including the
no parts returned to the factory unless requested -
standard per hour warranty labor rate - fair and reason-
able time limits established for various repair jobs with
reimbursement of service ‘dealer costs for parts used in
warranty repairs. We will continue to do everything we can to make servicing
accounts work easier and, if possible, more profitable.
There will be a tremendous opportunity, in our opinion, in the service
repairbusinessduring the next 10 to 15 years. There will be many new
mechanical labor saving devices produced which cannot help but demand
more, better, and faster repair shop service throughout the country.
Lawn-Boy will continue to develop new products and improve design of all
their lawn and gardening products from year to year.
THE OPPORTUNITY IS YOURS. IT’S UP TO You.

THE PURPOSE OFSAFETY SYMBOLS IS TO
ATTRACT YOUR ATTENTION TO POSSIBLE
DANGERS. THE SYMBOLS, AND THE EXPLA-
NATIONS WITH THEM, DESERVE YOUR
CAREFUL ATTENTlON AND UNDERSTAND-
ING. SAFETY WARNINGS DO NOT BY THEM-
SELVES ELIMINATE ANY DANGER; THE IN-
ARENOT SUBSTITUTES FOR PROPER ACCI-
STRUCTIONS OR WARNINGS THEY GIVE
DENT PREVENTION MEASURES.
Symbol Meaning
SAFETY Failure to obey a safety warning
may result in injury to you or to
others.
Advises you of information or in-
NOTE: structions vital to the operation or
maintenance of your equipment.
This mower is designed and intended for the purpose of
mowing (cutting) grass and, when specially equipped with
a grass bag, for bagging cut grass. Any use for purposes
other than those noted above could prove dangerous to
user or bystanders.
SAFETY WARNINGS
Prevent accidents. Use the following practices for operating
your mower safely. These warnings apply to all rotary, gasoline
recommended by LAWN-BOY and the Outdoor Power Equip-
engine powered mowers, regardless of manufacturer. They are
ment Institute. Inc., Washington, D.C.
CLEAR THE AREA
Clean the lawn of sticks, stones, wire, etc. They can be picked up
and hurled great distances by the blade. Mow only in cleaned
ares.
Keep children and pets away from vicinity of mower as you
would any cutting machinery.
WEAR PROPER ATTIRE
Don't wear loose fitting clothing.Provide some external protec-
tion for yourself by means of long, heavy denim trousers and
heavy shoes. Never mow when barefoot or wearing open sandals.
Safety shoes are recommended.
CHECK THE MOWER BEFORE USE
Check all nuts, bolts and fasteners for tightness, especially the
blade nut (torque blade nut 45-50 ft. lbs.). Disconnect spark
plug lead (Electric start models; also disconnect battery con-
nections) before check.
Keep all guards in place at all times.
Keep either cover plate or grass catcher chute with bag in place
and secure at all times.
Check grass or leaf bags for wear or deterioration. Replace bag if
necessary.
Have a competent serviceman make a thorough inspection of your
mower at least once a year.
HANDLE FUEL PROPERLY
Gasoline is extremely flammable and highly explosive under cer-
tain conditions. Always stop engine, and do not smoke or allow
open flames or spark when mixing fuel or refueling.
Do not fill fuel tank while engine is hot or running. Spilling fuel
on a hot engine may cause a fire or explosion.
To prevent possible explosion or ignition of vaporized fuel, do
not store mower with fuel in tank or carburetor in enclosure with
open flame. (Example: Furnace or water heater pilot light.)
Always store or transport mower with fuel shut-off valve in the
"OFF position.
Fill tank outdoors. Wipe up spilled gasoline. Replace cap
securely. Use an approved safety container to handle and store
gas. Keep engine free from accumulations of grass, leaves or
excessive grease. These combustible materials could result in a
fire.
Never start or run the engine inside where exhaust fumes can
collect. Carbon monoxide present in the exhaust is an odorless
and deadly gas.
KNOW YOUR CONTROLS
Learn how to stop the engine quickly. Be sure the control handle
is in "NEUTRAL" position (to the rear) before starting or
stopping self-ropelled models.
START AND MOW WITH CARE
Never allow anyone to operate your mower without complete
instructions. Teach all safety rules andoperatinginstructions to
all users. DO NOT ALLOW CHILDREN TOOPERATEMOWER.
Don't start the engine until you are ready to mow. Be sure
mower will not tip or roll during starting operation. When starting
engine, place one foot on top of blade housing s designated with
heel off the ground to aid stability. Never stand in front of
self-propelled mowers. Keep clear of discharge opening. Keep
hands and feet away from moving parts. Never place hands or
feet under the mower while blade is turning. Stop the engine and
make sure the blade has come to a complete stop and the spark
plug wire is disconnected, (Electric start models; disconnect battery
connections) before attempting to dean or unclog the catcher
assembly or discharge chute.
Alwayspush,never pull, a mower with the engine running. Mow
across face of slopes. Do not mow excessively steep slopes.
Control direction of mower by handpressureon the handle, not
foot pressure on the mower housing. Do not lag behind or let
mower pull you. Keep a firm hold on the handle and walk, never
run with mower. Mow in daylight or good artificial light. Never
operate equipment in wet grass. Always be sure of your footing.
Stop engine before changing or emptying catcher bag, pushing
mower across walks, drives, roads or before leaving operating
position, even for a moment.
If operating mower on uneven or rough ground, be especially
careful. Front of mower may drop lower than normal, and hidden
objects may be thrown by blade. Keep all four wheels on the
ground when mowing. I f mower is tipped while blade is turning,
blade is exposed and accidents can occur.
Avoid striking trees, walls, curbs or other solid objects with
mower. Never deliberately mow over any object. Exercise spe-
cial care when mowing around objects to prevent the blade
striking them. If an object is struck, or mower starts to vibrate.
stop engine immediately, remove spark plug wire (Electric start
models; also disconnect battery connections) and examine
mower for damage. Replace damaged parts before restarting
and operating mower.
MAKE ADJUSTMENTS CAREFULLY_
Do not overspeed engine or alter governor settings. Excess speed
Is dangerous and shortens mower life. Stand to one side and
keep feet and hands clear while making carburetor adjustments.
Height adjustments should be made only after engine and blade
are stopped. Disconnect spark plug lead (Electric start models;
also disconnect battery connections) prlor to performing service
on eng i ne or mower. Keep lead away from plug. On self-propelled
models be sure control is in "NEUTRAL" position.
Never rotateblade with hand or foot without first removing
spark plug wire (Electric start models; also disconnect battery
connections) to prevent starting.
REMOVE KEYS WHEN STORING
Electric start mowers cannot be started, even manually, with key
removed.
REPLACEMENT PARTS
Whenreplacement parts arerequired, use genuine OMC parts or
parts with equivalent characteristics including type, strength,and
material. Failure to do so may result in product malfunction and
possible injury to the operator and/or bystanders.
IT'S UP TO YOU. A POWER MOWER IS NO SAFER THAN ITS
OPERATOR.

SECTION 1 MOWERHISTORY TWO CYCLE THEORY-
DEVELOPMENT OF THE AMERICAN POWER MOWER
The following information
on thehistory of the de-
velopment of power mowing
in America has been col-
lected from the most reli-
able sources we could find.
1890 - This "One Horsepower"
Henderson Mower Was Popular.
Similar to First Patented Mowers.
The first mechanical mower of which we have any record was pat-
ented in England in 1830 by a Mr. Edwin Budding of Stroud, Glou-
cestershire. This mower moved on a massive iron roller and fea-
tured a reel blade that worked against a parallel bedplate. The
Budding mower gave us the still-popular principle of the reel-cutting
blade. 1500 of these were produced between 1833 and 1859. Suc-
cessors to this company are still in business, under the name of
Lawn Mower Works.
The first power was added in 1842, when a Mr. Shanks of "Shanks'
Mare" fame patented a Budding-type horse-drawn mower, In 1859
a mower using chain drive instead of the Budding gear drive was
patented - the Silens Messer mower.

The firstline of reasonably
moderate-priced mowers was
brought out by the firm of
Ransome,Sims and Jeffries,
Ltd. in the 1860's. These
mowers were of light con-
struction and produced in a
number of sizes with varying
features.
In , 1878, the Pennsylvania
Mower Company patented a
side-wheelmachinethat was
driven by' a train of gearing
instead of internal gear ring
and pinion.
The first gasoline powered
lawn mower was patented by
Mr. Edward Ransome in 1902,
and the first successful at-
tempt to market a gasoline
powered mower was made by
the Thomas Green firm in
1904.
The electric power mower made its appear-
ance in the early 1920's and rapidly gained
wide popularity. The Ransome firm also
mass-produced an electric mower several
years later which featured headlights for
night mowing.
Following World War I, mass production and
the general awakening of the American in-
dustrial giant brought forth a host of power
mower and hand mower manufacturers.
From 1918 to 1925 millions of the familiar
type hand-push reel mowers were made by
scores of manufacturers in the U.S. and
abroad. By 1925, however, the gasoline-
powered reel mower began to take a bigger
and bigger share of the market.
For example: in 1924, 880,000 hand-push
mowersretailingfor $7,000,000 weresold
in the U.S. The same year, 5,000 reel-type
power mowers were sold for $1,250,000.
1917 - Power Mowers of This Type Were 1920's - One of the First Rotary Power
Toolbox. the Belt Drive.
. Becoming Popular. Equipped Complete with Mowers, Produced in the Late 20's. Note
1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SERVICE BULLETIN REFERENCES

Toward the middle of the 1930's the rotary power mower, featuring a horizontally-mounted
cutting blade, began to appear on the American home scene. This was the first and most sig-
nificant advance in a century of lawn mowing.
Since World War II there have been great strides in the development of power mowers. The
rotary has become increasingly popular; and in 1958 approximately 90% of the power mowers
sold were rotaries, either self-propelled or push-propelled.
Lawn-Roy became the country's first Production-line manufacturers of complete power
mowers,includingengines,in the early 1950's when OutboardMarine bought out the Roto
Power Mower Company of Kansas City, Missouri, one of the very first rotary power manu-
facturers.
Power mower sales in 1971 exceeded 5,500,000 units. The walk-behind rotary accounted for
4,700,000, or 85% of all power mower sales according to the Outdoor Power Equipment Insti-
tute. About 80% of the 1971 sales were for the replacement of the 38,000,000 power mowers
currently in use in the United States. Sales of rider mowers and lawn tractors have grown to
over 800,000 units annually.
Lawn and gardenbusiness is booming and will continue to boom. Saturation? . . . it will
HELP, NOT HURT, the quality manufacturer.
1959 - The New Lawn-Boy QUIETFLITE
1934 - The 1934 "Lawn-Boy" was Manufac- ushered in the "Golden Age of Power Mow-
tured by Evinrude. Self-propelled Chain ing." Its moving and working parts are
Drive Reel Type. completely Sealed and Insulated. QUIET-
FLITE in 1959 was the Last Word in Modern
Quiet Power Mower Development.
SERVICE BULLETIN REFERENCES . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . , . 1-3

Thru the years Lawn-Boy has continuedto
improve in design and performance- of
Lawn-Boy products. This is one reason
why Lawn-Boy is one of the world leaders
in the industry. Lawn-Boy is one of the few
manufacturers that offers a complete choice
of models designed to fit all mowing re-
quirements. From the apartment dweller
to the estate owner Lawn-Boy offers a
choice to satisfy all lawn and garden re-
quirements.
Tests have shown the Lawn-Boy D-400 Ser-
ies, 2 Cycle Engine, to be one of thebest
engines available. The heart of your mower
is the engine and the D-400 Series is de-
signed to offer years of dependable service.
1972 Lawn-Boy introduced its first Solid State
(CD) D-600 Series engine. Available with manual
or electric start - self-propelled or push pro-
pelled type models. The solid state ignition sys-
tem has no moving parts, is completely enclosed
reducing ignition failure while producing up to
30,000 volts. No points, coil or condenser to
replace, offering longer spark plug life. The all
new carburetor used on the D-600 Series engine is
completely automatic. No adjustments other
than an atmospheric pressure adjustment is re-
quired. A new primer system forces compressed
air into the float chamber which forces fuel into
the carburetor venturi. This method of priming is
effective and consequently, one prime is usually
sufficient to start the engine. The larger muffler
design reduces noise and exhaust down into the
turf.
1-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SERVICE BULLETIN REFERENCES

Lawn-Boy developed the revolutionary
CORDLESS ELECTRIC MOWER - powered
by 36 volts this compact mower contains all
the engineering "know-how" and safety fea-
tures of gasoline operated mowers. Exces-
sive noise and exhaust fumes are eliminated.
One more FIRST for Lawn-Boy.
In the future Lawn-Boy will continue to
improve to offer you, the dealer, and your
customers the best product available.
SERVICE BULLETIN REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . 1-5

THE NEW GENERATION
Thenewgenerationseries ofLawn-Boymowerscombines
68 years of 2-cycle technology with advancedengineering
and manufacturing procedures. The final result is an all
new look from the "grass up." 21 fewer parts, less weight,
and introducing an all NEW "F" series Lawn-Boy engine
which produces 20 to 30% more usable power.
Lawn-Boy has retained and refined all the outstanding
features that have made us famous.
Easy fingertip starting - a reduced4 to 1 gear ratio re-
sulting in the easiest starting
mower in Lawn-Boy's history.
Quiet operation - featuring a new exhaust system. The
welded muffler assembly contains an
additional baffle and muffler tube.
Designed as a one-piece assembly
secured to the mower with only three
screws.
Super vacuum action - the design of the mower housing
and famous durable Lawn-Boy
high lift blade has been improved
to discharge clippings into the
rear of the grass bag -- this creates
a well manicured mowing appear-
ance. Also added under the deck
is a crankshaft support located
approximately 2 inches above the
blade to provide additional pro-
tection for the crankshaft and
crankcase.
Thenewgenerationbegan in the summer of-1972. WHY?
1. Contain fewer parts.
2. Design a new engine which develops more power at
lower RPMS which meets or exceeds OPEI safety
standards.
1973: First engineering prototype "F" engine run.
1974: New fuel and governor system developed and
1975: In May, first factory "die cast" engine tested.
1975: In October, first units released for extensive field
1977: In October, full factory production began after
tested.
testing.
- 2 years of thorough and extensive testing.
This is not the end -- rather, the beginning of a NEW
GENERATION for us the manufacturer and you the service
dealer.
1983: In July, after 9 years of research and development,
Lawn-Boy started producing compliance lawn
mowers that featuredtwo different blade stopp-
ing systems.
One is the blade, brake, clutch (BBC) system
which stops the blade within 3 seconds after the
operator releases the bail. The engine continues
to run with this system.
The other is a flywheel brake system which stops
both the blade and engine within 3 seconds after.
the operator releases the bail.

THE NEW GENERATION "F" SERIES 2 CYCLE
UNITIZED
POWERHEAD
An automated,
computer-controlled machine
manufactures two pieces into
a cylinder blockassembly
that has uniformity
and precision.
PRESSURE-BACK
PISTON RING
Minimizes compression blowby-
to increase usable power,
improve fuel economy and
aid starting ease.
NO-TUNE-UP
ELECTRONIC IGNITION \
I
ENGINE
FRICTION-REDUCING
NEEDLE BEARINGS
The crankshaft, top and bottom,
as well as the connecting rod,
are nestled in precision
needle bearings, resulting in
free running, smooth
operation. Silverplated
bearing liner at the big end
of the connecting rod.
I
Lawn-Boy mowers meet or exceed
current A.N.S.I. B71. Ib 1977
safety standards for rotary-type
mowers. We proudly display
this Outdoor Power Equipment
Institute seal on each machine.
\
MORE
USABLE POWER
Displacement is increased
from 6.6 to 7.7 cubic inches.
This and other improvements
add 20-30% more usable power.
SERVICE BULLETIN REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7
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LAWN BOY GARDEN EQUIPMENT Service Repair Manual 1950-1988
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Description
Fix your Lawn Boy equipment fast. This service repair manual covers every model from 1950 to 1988, giving you the exact procedures to handle tune-ups, overhauls, fuel system work, and seasonal maintenance. Whether it's blade replacement, engine rebuild, or transmission repair, you'll find diagrams, torque specs, and troubleshooting guides for every job.
Buy it once, download instantly, and start working. You get access to the complete manual with exploded parts views, wiring schematics, and step-by-step instructions. No subscription needed. No waiting. Perfect for weekend mechanics and serious DIY gardeners who want to keep their vintage Lawn Boy running strong.