Bolens 979 User Manual
OPERATOR’S MANUAL
21” Self-Propelled
Mower
Model Number
979
IMPORTANT: READ SAFETY RULES AND INSTRUCTIONS CAREFULLY
Warning: This unit is equipped with an internal combustion engine and should not be used on or near any unimproved forest-
covered, brush-covered or grass-covered land unless the engine’s exhaust system is equipped with a spark arrester meeting
applicable local or state laws (if any). If a spark arrester is used, it should be maintained in effective working order by the operator.
In the State of California the above is required by law (Section 4442 of the California Public Resources Code). Other states may have
similar laws. Federal laws apply on federal lands. A spark arrester for the muffler is available through your nearest engine authorized
service dealer or contact the service department, P.O. Box 368022 Cleveland, Ohio 44136-9722.
MTD PRODUCTS INC. P.O. BOX 368022 CLEVELAND, OHIO 44136-9722
PRINTED IN U.S.A.
FORM NO.
770-10075B.fm
(10/00)
TABLE OF CONTENTS
Content Page
Important Safe Operation Practices...................................................................3
Slope Gauge......................................................................................................6
Assembling Your Lawn Mower...........................................................................7
Know Your Lawn Mower ....................................................................................8
Operating Your Lawn Mower .............................................................................9
Making Adjustments ..........................................................................................11
Maintaining Your Lawn Mower...........................................................................12
Troubleshooting.................................................................................................16
Parts List............................................................................................................18
FINDING MODEL NUMBER
This Operator’s Manual is an important part of your new lawn mower. It will help you assemble, prepare and
maintain the unit for best performance. Please read and understand what it says.
Before you start assembling your new equipment, please locate the model plate on the
equipment and copy the information from it in the space provided below. The information on the
model plate is very important if you need help from our Customer Support Department or an
authorized dealer.
• You can locate the model number by looking down at the rear of the deck. A sample model plate is
explained below. For future reference, please copy the model number and the serial number of the
equipment in the space below.
(Model Number)
(Serial Number)
MTD PRODUCTS INC
CLEVELAND, OHIO 44136
Copy the model number here:
Copy the serial number here:
CALLING CUSTOMER SUPPORT
If you have difficulty assembling this product or have any questions regarding the controls, operation or
maintenance of this unit, please call the Customer Support Department.
Call 1- (330) 220-4MTD (4683) or 1- (800)-800-7310 to reach a Customer Support
representative. Please have your unit’s model number and serial number ready when you
call. See previous section to locate this information. You will be asked to enter the serial
number in order to process your call.
For more details about your unit, visit our website at www.yardman.com
2
SECTION 1: IMPORTANT SAFE OPERATION PRACTICES
WARNING: This symbol points out important safety instructions which, if not followed, could
endanger the personal safety and/or property of yourself and others. Read and follow all instructions in
this manual before attempting to operate this machine. Failure to comply with these instructions may
result in personal injury. When you see this symbol - heed its warning.
WARNING: Engine Exhaust, some of its constituents, and certain vehicle
components contain or emit chemicals known to State of California to cause cancer
and birth defects or other reproductiv e harm.
DANGER: This machine was built to be operated according to the rules for safe operation in this
manual. As with any type of power equipment, carelessness or error on the part of the operator can
result in serious injury. This machine is capable of amputating hands and feet and throwing objects.
Failure to observe the following safety instructions could result in serious injury or death.
General Operation
1. Read this operator’s manual c arefully in its e ntirety
before attempting to a ssembl e this mac hine. Read,
understand, and fo llow al l instruct ions on th e machin e
and in the manua l(s) befo re operatio n. Be com pletely
familiar with the c ontrols and the proper use o f this
machine before operating it. Keep this manual in a safe
place for future and re gular refe rence and for ordering
replacement parts.
2. This machine is a precision piece of power equipment,
not a plaything. Th erefore, exercise extre me caution at all
times. Your unit has been designed to p erform one job: to
mow grass. Do not u se it for any other purpose.
3. Never allow childre n under 14 y ears old to operate this
machine. Children 14 years old and over should rea d and
understand the op eration in struction s and sa fety rules i n
this manual and should be trained and sup ervised b y a
parent. Only respons ible indiv iduals who a re famili ar with
these rules of s afe operati on shoul d be allow ed to us e
this machine.
4. Thoroughly inspect the area wh ere the equipment i s to
be used. Remove al l stones, sticks , wire, bones, toys and
other foreign objec ts which could b e tripped over or
picked up and th rown by th e blade. T hrown obje cts can
cause serious persona l injury . Plan your m owing patte rn
to avoid discharge of materi al toward ro ads, sid ewalks,
bystanders and the like. Also, avo id discharging material
against a wall or obstructi on which m ay cause
discharged material to ri cochet back tow ard the operator.
5. To help avoid blade contact or a thro wn object injury, stay
in the operator zo ne behind the hand les and keep
children, bystanders , helpers a nd pets a t least 7 5 feet
from the mower wh ile it is in opera tion. Stop machine if
anyone enters the area.
6. Always wear safet y glasses or safety goggles during
operation and while performing an adjustment or repair to
protect your eyes. T hrown ob jects whi ch ricochet can
cause serious inj ury to the eyes.
7. Wear sturdy, rough-sol ed work shoes a nd close-fi tting
slacks and shirts . Shirts an d pants that cove r the a rms
and legs and steel -toed shoes are recommend ed. Never
operate this machin e in bare feet, san dals, sl ippery or
light weight (e.g. c anvas) sho es.
8. Do not put hands o r feet near rotating p arts or un der the
cutting deck. Con tact with the blade can am putate ha nds
and feet.
9. A missing or damaged discharg e cover can cause b lade
contact or thrown ob ject inj uries.
10. Many injuries occur as a resul t of the mower being pul led
over the foot during a fall caused by slipping or tripping.
Do not hold on to the mower if you are falling; releas e the
handle immediately .
11. Never pull the mowe r back to ward yo u while y ou are
walking. If you mus t back th e mower aw ay from a wall or
obstruction first look down and behind to avoid trippi ng
and then follow these st eps:
a. Step back from the mower to fu lly exte nd your
arms.
b. Be sure you are well balance d with sure footing.
c. Pull the mower back slowly, no more than half way
toward you.
d. Repeat these steps as neede d.
12. Do not operate the m ower whi le under t he influe nce of
alcohol or drugs.
13. Do not engage the self-pro pelled mechan ism on uni ts so
equipped while st arting engine.
14. The blade control handle is a safety device. Never
attempt to bypas s its operat ion. Doi ng so m akes the
safety device inoperat ive and may result in per sonal
injury through contact with the rotating blade. The blade
control handle m ust opera te easily i n both di rections and
automatically return to the di sengaged positio n when
released.
15. Never operate the mow er in wet gra ss. Always be sure of
your footing. A s lip and fa ll can c ause se rious person al
injury. If you fee l you are lo sing yo ur footi ng, releas e the
blade control han dle immedi ately an d the bla de will stop
rotating within three second s.
16. Mow only in daylig ht or in goo d artifici al light. Wa lk, never
run.
17. Stop the blade wh en crossin g gravel drives, wa lks or
roads.
18. If the equipment should start to vibrate abnormally, stop
the engine and check immedia tely for the cause .
Vibration is gener ally a warn ing of tro uble.
19. Shut the engine off and wa it until t he bla de come s to a
complete stop before removi ng the grass catcher or
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unclogging the c hute. The cutting b lade co ntinues t o
rotate for a few seconds afte r the engine is shut off. Neve r
place any part of the body in the b lade area until yo u are
sure the blade has stoppe d rotating .
20. Never operate mower wi thout prop er trail shield,
discharge cover , grass c atcher, blad e cont rol handle or
other safety protec tive dev ices in p lace and working.
Never operate mower with damaged sa fety devices.
Failure to do so, ca n result i n persona l injury .
21. Muffler and engine be come hot and c an cause a burn . Do
not touch.
22. Only use parts and acc essories made fo r this machine by
the manufacturer. F ailure to do so, c an result in perso nal
injury.
23. If situations occur which are not covered in this manua l,
use care and good judgment. Cont act your dealer for
assistance. Tel ephone 1- 800-800-731 0 for the name of
your nearest dealer.
Slope Operation
Slopes are a major f actor re lated to slip and fall accid ents
which can result in seve re inju ry. Opera tion on s lopes
requires extra cauti on. If you feel une asy on a slope, do not
mow it. For your safet y, use th e slope gauge in cluded a s part
of this manual to me asure slopes before operati ng this unit on
a sloped or hill y area. If the slop e is greater than 15 d egrees,
do not mow it.
Do:
1. Mow across the face of sl opes; never up and down.
Exercise extreme cauti on when changing d irection on
slopes.
2. Watch for holes, ru ts, rocks, hidden ob jects, o r bumps
which can cause you to s lip or tri p. Tall grass c an hide
obstacles.
3. Always be sure of your footi ng. A slip and fall can ca use
serious personal in jury. If y ou feel y ou are lo sing yo ur
balance, release the blade c ontrol han dle imm ediately ,
and the blade w ill stop rotating wi thin 3 se conds.
Do Not:
1. Do not mow near drop-offs, ditches or embankments, you
could lose your footing o r bala nce.
2. Do not mow slopes gre ater than 15 degrees as shown on
the slope gauge.
3. Do not mow on wet grass. U nstable footing c ould cau se
slipping.
Children
Tragic accident s can occu r if the o perator is not al ert to the
presence of childre n. Chil dren are of ten attrac ted to the
mower and the mowi ng activ ity. They do not unde rstand the
dangers. Never assum e that c hildren wil l remain where you
last saw them.
1. Keep children out of t he mow ing area a nd under the
watchful care of a responsi ble adul t other than the
operator.
2. Be alert and turn mower off if a child enters the area.
3. Before and while moving backw ards, look behin d and
down for small ch ildren.
4. Use extreme care when approaching blind corners,
doorways, shrubs, tree s, or othe r objects th at may
obscure your visi on of a child wh o may ru n into the
mower.
5. Keep children away from hot or running engines . They
can suffer burns from a hot muffler.
6. Never allow childre n under 14 y ears old to operate a
power mower. Children 14 years old and over should
read and understand the operation in structions and
safety rules in this manual and sho uld be tra ined and
supervised by a parent.
Service
Safe Handling Of Gasoline:
1. To avoid personal i njury or property d amage use extrem e
care in handling gasolin e. Ga soline i s extrem ely
flammable and t he vapors are expl osive. Serio us
personal injury can occur when gasoline is spilled on
yourself or your clothes which can ignite.
2. Wash your skin and change cl othes immedia tely.
3. Use only an appro ved gaso line container .
4. Never fill containers inside a vehic le or on a tru ck or
trailer bed with a plast ic liner. Always place contai ners on
the ground away fro m your v ehicle b efore fill ing.
5. When practical, re move ga s-powered e quipment from
the truck or traile r and refue l it on t he ground. If this i s not
possible, then refuel such equipment on a trailer with a
portable containe r, rather tha n from a gasoline dispens er
nozzle.
6. Keep the nozzle in contact with the rim of the fuel tan k or
container opening at al l times until fueling is comp lete. Do
not use a nozzl e lock-open devi ce.
7. Extinguish all cig arettes, c igars, pi pes and o ther sources
of ignition.
8. Never fuel machin e indoors becaus e flamma ble vapo rs
will accumulate in the area.
9. Never remove gas cap or ad d fuel w hile the engine i s hot
or running. Allow e ngine to cool at l east tw o minutes
before refueling.
10. Never over fill fue l tank. F ill tank to no mo re than ½ inch
below bottom of fi ller neck to provide space fo r fuel
expansion.
11. Replace gasoline cap and tighten sec urely.
12. If gasoline is spilled, w ipe it off the engine and equipm ent.
Move unit to another area. Wait 5 minutes before starting
the engine.
13. Never store the machine or fuel c ontainer i nside whe re
there is an open flame, spark or pilot light as on a w ater
heater, space heate r, furnac e ,cloth es dryer or other gas
appliances.
14. To reduce fire hazard , keep mow er free of grass, leav es,
or other debris bu ild-up. C lean up oil or fue l spilla ge and
remove any fuel soaked debris.
15. Allow a mower to cool at least 5 minutes before storing.
General Service:
1. Never run an engine indoors or in a poorly ventil ated
area. Engine exha ust conta ins carb on monox ide, an
odorless and de adly gas.
2. Before cleaning, repairing, or inspecting, make certain
the blade and al l moving parts ha ve stopp ed. Disco nnect
the spark plug wi re and grou nd again st the en gine to
prevent unintended star ting.
4
3. Check the blade a nd engine mountin g bolts a t frequ ent
intervals for proper tigh tness. Also, visu ally inspec t blade
for damage (e.g., b ent, crack ed, worn) R eplace bl ade
with the original equip ment manufacture’s (O. E.M.) blade
only, listed in this manual . “Use of p arts which do not
meet the original equipment specific ations m ay lead to
improper performance and com promise sa fety!”
4. Mower blades are s harp and can cut. Wrap the b lade or
wear gloves, and u se extra caution when se rvicing the m.
5. Keep all nuts, bolts, and screws tight to be sure the
equipment is in safe work ing cond ition.
6. Never tamper with safety devices. Check their proper
operation regularly.
7. After striking a foreign o bject, stop the engine, dis connect
the spark plug wire and grou nd agains t the engine.
Thoroughly inspect the mower for any da mage. R epair
the damage before st arting and operat ing the mow er.
8. Never attempt to ma ke a w heel or c utting hei ght
adjustment while the engin e is runn ing.
9. Grass catcher componen ts, discharge cover, and trail
shield are subject to wear and dama ge which could
expose moving pa rts or allo w objec ts to be thrown. For
safety protection, frequentl y check componen ts and
replace immediatel y with original equipm ent
manufacturer’s (O.E.M .) parts only , listed in this ma nual.
“Use of parts which do not m eet the ori ginal eq uipment
specifications ma y lead t o imprope r performan ce and
compromise safety!”
10. Do not change t he engine governor setting o r overs peed
the engine. The go vernor co ntrols th e maxim um safe
operating speed o f the engi ne.
11. Maintain or replac e safety and ins truction labels, a s
necessary.
12. Observe proper disp osal law s and regulation s. Improp er
disposal of flui ds and mate rials ca n harm th e
environment.
WARNING - YOUR RESPONSIBILITY: Restrict the use of th is power mac hine to p ersons wh o read,
understand and fo llow th e warnings and ins tructions in this manual a nd on the mach ine.
NOTE: Not all safety labels shown may apply to your lawn mower.
5
SECTION 2: SLOPE GAUGE
Use this page as a guide to determine slopes where you may not operate safely. Do not operate your lawn mower
on such slopes.
Operate RIDING mowers up and down slopes, never across the face of slopes.
Operate WALK-BEHIND mowers across the face of slopes, never up and down slopes.
Do not mow on inclin es with a s lo pe i n e xces s of 1 5 de gr ees ( a r ise o f approximately 2-1/2 f eet every 10 feet). A ridi ng m owe r could
overturn and cause serio us injur y. If oper ating a walk-be hind mo wer on suc h a slope, i t is ex tremely diffic ult to maint ain your footing
and you could slip, resulting in serious injury.
F
O
L
D
O
N
D
O
T
T
E
D
L
I
N
E
,
R
E
P
R
E
S
E
N
T
I
N
G
A CORNER OF A BUILDING
OR A FENCE POST
SIGHT AND HOLD THIS LEVE L WITH A VERTICAL TREE
A POWER POLE
WARNING
15°
A
1
5
°
S
L
O
P
E
6
SECTION 3: ASSEMBLING YOUR LAWN MOWER
IMPORT ANT :
in the engine. Be certain to service engine with gasoline
and oil as instructed in the separate engine manual
before operating your mower.
NOTE: Reference to right or left hand side of the mower
is observed from the operating position.
This unit is shipped without gasoline or oil
Removing Unit From Carton
• Remove staples, break glue on top flaps, or cut
tape at carton end and peel along top flap to open
carton.
• Remove loose parts if included with unit (i.e.,
operator’s manual, oil, etc.)
• Cut along corners, lay carton down flat, and remove
packing material.
• Roll or slide unit out of carton and check carton
thoroughly for loose parts.
Loose Parts in Carton
• Grass Bag
• Grass Bag Adapter
• Side Discharge Chute
• Hardware Pack
Handle Assembly
Wing Nut
Handle Mounting
Bracket
Figure 2
• Remove the hairpin clips from the outer hole in the
weld pins on the handle mounting brackets. Using a
pair of pliers, squeeze one leg of the lower handle
against the handle mounting bracket. Insert the
hairpin clip into the inner hole on the weld pin.
Repeat on other side. See Figure 3.
• After moving the hairpin clip, insert the carriage bolt
from hardware pack in the upper hole on the handle
mounting bracket and secure with plastic wing nut
from the hardw are pa ck. Re peat on oth er si de.
Disconnecting Spark Pl ug Wire
• Before setting up your lawn mower, disconnect the
spark plug wire from the spark plug and ground
against the engine. See Figure 1.
Spark Plug
Wire
Figure 1
Spark
Plug
Setting Up Y our Lawn Mower
• Remove grass bag and other loose parts from unit
and set it aside.
• Lift up and pull back on the upper handle to raise
the handle into the operating position. Make
certain the lower handle is seated securely into the
handle mounting brackets. Tighten the wing nuts
on each side of the handle (carriage bolts must be
seated properly into the handle). See Figure 2.
NOTE: Your mower is shipped with the handle in the
higher height position. If you wish to lower the height of
the handle, refer to the Adjustment Section at this time.
Carriage Bolt
Lower
Handle
Wing Nut
Handle Mounting
Bracket
Figure 3
• Fasten the cables to the lower handle with the two
cable ties found on the lower handle. Be sure to
insert the post on the cable ties into the holes
provided on the lower handle. These holes may be
found on either the inside or outside of the handles.
Pull the cable ties tight and trim off the excess.
See Figure 4.
Cable Tie
Lower
Handle
Figure 4
Inner Hole
Hairpin
Clip
7
NOTE: Make certai n the drive cable is routed a round
the outside and above th e lower handle so it does not
interfere with attaching the grass bag.
Lower
Handle
• The rope guide, which is connected to the support
rod, is located on the right side of lower handle.
See Figure 5.
• With the spark plug wire disconnected and
grounded, hold the blade control handle against the
upper handle, and pull the starter rope out of the
engine. Release the blade control handle. Slip the
starter rope into the rope guide.
SECTION 4: KNOW YOUR LAWN MOWER
Read this operator’s manual and safety rules before
operating your lawn mower. Compare the illustrations
in Figure 6 with your lawn mower to familiarize yourself
with the location of various controls and adjustments.
Save this manual for future reference.
WARNING: The operation of any lawn
mower can result in foreign objects being
thrown into the eyes, which can damage
your eyes severely. Always wear safety
glasses while operating the mower, or
while performing any adjustments or
repairs on it.
Recoil Starter
The recoil starter is attached to the right lower handle.
Stand behind the unit and pull the recoil starter to start
the unit. See Figure 6.
Blade Control Handle
The blade control handle is located on the upper handle
of the mower. The blade control handle must be
depressed in order to operate the unit. Release blade
control handle to stop engine and blade. See Figure 6.
WARNING: This blade contro l mechanism
is a safety device. Never attempt to bypass
its operations.
Cutting Height Adjustment Lever
The cutting height adjustment lever is located above
the left rear wheel. To adjust the cutting height, refer to
the Adjustment Section in this manual. See Figure 6.
Drive Clutch Control
The drive clutch control is located on the upper handle.
Squeeze the drive control to engage the drive system.
Release the clutch control to disengage the drive
system. Release the clutch control to slow down when
approaching an obstacle, making a turn, or stopping.
See Figure 6.
Shift Lever
The shift lever is located on the drive clutch control
housing on the upper handle. This lever is used to
select the forward speed of the mower. When changing
speed selection, release the drive clutch control. See
Figure 6.
NOTE: Move the shift lever only when the engine is
running. Changing the shift lever setting with the
engine off can cause damage to t he mower.
Engine Controls
See the separate engine manual for the location and
function of the controls on the engine.
Stopping Engine
• Release blade control handle to stop the engine
• Disconnect spark plug wire and ground it to the
Drive Clutch
Control
Recoil
Starter
Starter
Rope
Rope
Guide
and the blade.
post on the engine.
Discharge
Chute
Support
Rod
Figure 5
Blade Control
Handle
Shift Lever
Cutting Height
Adjustment Lever
Mulching
Plug
Figure 6
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