SMALL ENGINE
®
A step-by-step guide to maintaining your small engine
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IMPORTANT SAFETY INFORMATION AND
In the USA and Canada,
our 24 hour hotline is:
INSTRUCTIONS FOR
ENGINE SELECTION
1-800-233-3723
ENGINE INSTALLATION
Briggs & Stratton Corporation
Milwaukee, Wisconsin 53201
ENGINE OPERATION
Keep these instructions for future reference.
Before installing and operating this engine
read and observe all warnings, cautions and
instructions on both sides of this sheet, on the engine,
and in the operating & maintenance instructions.
NOTE: This sheet of instructions and safety information is not meant to cover all
possible conditions and situations that may occur. Read entire Operating &
Maintenance Instructions for this engine AND the instructions for the equipment
this engine powers. Failure to follow instructions and safety information could
result in serious injury or death.
HAZARD SYMBOLS AND MEANINGS
The safety alert symbol
information about hazards that can result in personal injury.
( )
is used to identify safety
A signal word (DANGER, WARNING, or CAUTION) is used with the
alert symbol to indicate the likelihood and the potential severity of
injury. In addition, a hazard symbol may be used to represent the type
of hazard.
Fire
Explosion
Moving Parts
DANGER indicates a hazard which, if not avoided,
will result in death or serious injury.
Toxic Fumes
Hot Surface
Shock
WARNING indicates a hazard which, if not
avoided, could result in death or serious injury.
CAUTION indicates a hazard which, if not avoided,
might result in minor or moderate injury.
Kickback
CAUTION, when used without the alert symbol,
indicates a situation that could result in damage to
the engine.
(OVER)
FORM MS-6445-01/03
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ENGINE SELECTION
[8]
[9]
All engine parts, including fuel
cap, spark plug, muffler, air
cleaner, and covers and guards
for drive components (gears,
belts, shafts, couplings, etc.)
must be in place before attempt-
ing to start engine.
WARNING
WARNING
WARNING
Failure to select the correct engine could
result in fire or explosion.
If engine is installed on walk
behind lawn mower, all mower
components, including cutting
blade, must be correctly
installed before attempting to
start engine.
•
•
•
Some engines are unique and designed for specific applications
or types of equipment. If this engine will be used to build new
equipment, contact Briggs & Stratton to ensure that the engine is
appropriate for the intended use.
Note:For all Go-karts use only a model 136200 series engine,
which offers improved safety and performance.
Replacement engines should be the same model as the original
engine, or be the Briggs & Stratton designated replacement
engine. Refer to the Operation & Maintenance Instructions for
engine identification information.
[10]
[11]
When working on the engine or
equipment, remove spark plug
wire from spark plug. For electric
start, remove negative wire from
battery.
WARNING
WARNING
Do not check for spark with
spark plug removed. Use Briggs
& Stratton spark tester #19368.
Note:For all Go-karts use only a model 136200 series engine,
which offers improved safety and performance.
Do not use Briggs & Stratton engines on 3-wheel All-Terrain
Vehicles (ATVs), motor bikes, air craft products, or vehicles
intended for use in competitive events. Briggs & Stratton does not
approve of or authorize such uses.
ENGINE OPERATION
ENGINE INSTALLATION
WARNING
[1] Do not attempt to install this engine if you do not have the
appropriate tools and knowledge of small engine installation
procedures. Use only Briggs & Stratton parts. Contact your
Authorized Service Dealer for assistance.
When adding fuel:
[2] Do not modify the engine in any way without Briggs & Stratton
factory approval. Any such modification is at the owner’s sole
risk.
[3] If the exhaust system on the old engine was supplied by the
equipment manufacturer, you must transfer the exhaust
system and related components (original muffler and related
pipes, brackets, clamps, and shields) to the new engine. All
components must be in good condition.
Turn engine off and let engine cool at least 2 minutes before
removing gas cap.
Fill fuel tank outdoors or in well-ventilated area. Fill tank to about
1 inch below lowest portion of neck to allow for fuel expansion.
Keep gasoline away from sparks, open flames, pilot lights, heat,
and other ignition sources.
[4]
Install muffler (and muffler de-
flector if used) so outlet points
away from operator, fuel tank,
and equipment, and so muffler
heat will not damage or deform
engine and components.
WARNING
WARNING
When starting engine:
Remove all external equipment/engine loads.
Wait until spilled fuel is evaporated. Start engine outdoors.
Pull cord slowly until resistance is felt, then pull rapidly.
[5]
Ensure all fuel lines and fittings
are properly assembled and do
not leak. Replacement parts
must be the same model as the
original.
WARNING
If engine floods, set choke to OPEN/RUN, place throttle in FAST
and crank until engine starts.
WARNING
[6]
Ensure all wiring, including
safety switches and engine
shut-off components are com-
pletely installed and functioning
properly.
WARNING
When operating equipment:
Do not tip engine or equipment at angle which causes gasoline to
spill.
Run engine outdoors. Do not run in enclosed area, even if doors
or windows are open.
[7] Set engine speed to equipment manufacturer’s specification.
Refer to equipment manufacturer’s manual. Do not tamper with
governor springs, or other parts that will increase engine speed
above specification.
Do not choke carburetor to stop engine.
FORM MS-6445-01/03
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INTRODUCTION TO ENGINES
The carburetor draws in fuel from the fuel tank
A flywheel brake and stop switch are included
on engines for equipment such as mowers that
require constant supervision. The two compon-
ents are designed to stop the engine if you
release the controls.
The four-stroke small engine that powers
your lawn mower, tiller, generator and many
other types of equipment is a gasoline engine
that generates the precise amount of power
necessary to get the job done. Here’s how the
components in your engine interact.
and outside air to form a combustible vapor that
is fed into the combustion chamber.
Intake and exhaust valves open and close at
precisely timed intervals to let air and fuel enter
the engine and to let spent gases exit.
An air vane or flyweights monitor engine
RPMs so the governor can maintain the selected
engine speed.
Engine components &
their function
The rewind cord is pulled to start the
combustion process. On some models, a
starter motor replaces the rewind, drawing
on battery power to start the engine.
The piston is pushed through the cylinder by the
force of expanding gases. The piston’s motion
causes the crankshaft to turn. Momentum then
carries the piston back toward the top of
the cylinder.
Cooling fins help reduce engine tempera-
tures when air circulates across the hottest
engine surfaces.
Oil stored in the crankcase circulates through
the engine to lubricate key components like the
piston and crankshaft and to provide generalized
cooling by drawing away heat from internal
engine surfaces.
Revolving magnets work in conjunction with the
ignition armature and spark plug to produce a
spark in the combustion chamber.
Parts of the small engine – front view
Parts of the small engine – side view
Fuel tank and shroud
Fuel cap
Fuel tank and shroud
Rewind rope
Rewind
Rewind
Oil fill cap
Blower housing
Blower housing
Flywheel
Air cleaner element
Primer bulb
Carburetor
Ignition armature
Flywheel
Flywheel brake
Dipstick
Spark plug lead
Intake valve spring
Intake valve
Piston
Connecting rod
Crankcase
Cylinder head
Piston
Air cleaner cover
Spark plug
Cylinder head
Muffler
Intake valve
Exhaust valve
Engine block
Crankshaft
Exhaust valve
Crankshaft
Exhaust valve spring
THE GUIDE TO SMALL ENGINES 3
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MAINTENANCE
Regular maintenance schedule
You can avoid many small engine problems and save money on parts and
repairs if you follow a regular maintenance schedule. Make good maintenance
a habit when your engine is new, and always consult your owner’s manual for
special guidelines for your make and model. Service the engine more
frequently if you use it heavily or under dusty or dirty conditions.
After the first five hours of use:
• Change the oil and filter.
After each use:
• Check the oil.
• Remove debris around the muffler.
Every 25 hours or every season:
• Change the oil if operating under heavy load
or in hot weather.
• Service the air cleaner assembly.
• Clean the fuel tank and line.
• Clean the carburetor float bowl, if equipped.
• Inspect the rewind rope for wear.
• Clean the cooling fins on the engine block.
• Remove debris from the blower housing.
• Check engine compression.
• Inspect governor springs and linkages.
• Inspect ignition armature and wires.
• Inspect the muffler.
• Check the valve tappet clearances.
• Replace the spark plug.
• Adjust the carburetor.
• Check the engine mounting bolts/nuts.
Every 100 hours or every season:
• Clean the cooling system.*
• Change the oil filter, if equipped.
• Decarbonize the cylinder head.
*Clean more often if the engine operates under
dusty conditions or in tall, dry grass.
4 THE GUIDE TO SMALL ENGINES
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CHECKING & CHANGING OIL
When you pour fresh oil into the crankcase, it’s a golden or amber
color. Gradually, the heat, dirt particles and agitated air in the
crankcase cause the oil to darken. Dark oil is not only dirty; it has also
lost much of its ability to coat and protect engine components.
Tools & materials:
Socket wrench set, box\wrench or adjustable wrench,
screwdriver or hex key, oil filter or pipe wrench
(for models with filters), oil drain pan, funnel.
Manufacturers recommend changing the oil in your small engine after
every 25 hours of operation. For a new engine, you’ll also need to
change the oil after the first five hours of operation. New engines
require this extra step to flush out small particles that accumulate
naturally during the break-in period.
Time required:
30 minutes.
Hours of use are just one factor in determining how often the oil
should be changed; the amount of wear and tear is equally important.
Just like the oil in a vehicle operated in extremely dirty or dusty
conditions or at high speeds, the oil in a lawn mower or other small
engine breaks down faster under tough conditions, such as wet grass,
heavy dust, high temperatures and rough or hilly terrain.
Changing the oil
Once you decide the oil needs changing,
check your owner’s manual to determine the
type of oil, and make sure you have enough
on hand. Then, run the engine for several
minutes. Draining the oil while it’s warm will
carry off many floating particles that would
otherwise settle in the engine.
Checking the oil
Make it a habit to check the oil level and
appearance each time you’re about to start a
small engine. Checking the oil while the
engine is cold and most of the oil is in the
crankcase yields the most accurate reading.
You won’t need to change or add oil every
time. But you’ll ensure a better-running
engine and avoid problems down the road if
you keep the crankcase full and change the
oil on schedule and any time the oil loses its
amber hue.
1. Stop the engine, disconnect the spark
plug lead and secure it away from the spark
plug. Then, locate the oil drain plug. On
A
mowers, the plug is typically below the deck
and may be obscured by a layer of grass and
debris.
2. Wipe the area with a rag to prevent debris
from falling into the crankcase when you
open the drain plug. Tilt the mower deck and
position some newspaper and an oil pan or
jug beneath the mower. Use a socket wrench
to turn the plug counterclockwise, allowing
the old oil to drain (photo A). If the plug also
serves as a fill cap, it may have two prongs so
you can loosen it by hand or use a
1. Start by locating the oil fill cap on the
crankcase (photo A). Fill cap locations vary,
depending on the make and model of your
engine. On newer models, look for an oil can
A
symbol or the word “oil” or “fill” stamped on
the plug. On small tractors, you may have to
lift the hood to locate this cap.
screwdriver or hex key for additional torque.
B
Replace the drain plug by twisting clockwise
and tightening with a box wrench or
adjustable wrench.
Some engines contain either an extended oil
fill tube or a standard fill hole with a dipstick
for inspection. Others require you to remove
the fill cap to check that the oil is at the fill
line or the top of the fill hole.
3. If your engine has a filter, replace it at
least once a season, more often under heavy
use. Replace the filter by twisting counter-
clockwise on the body, using a filter wrench
or pipe wrench.
2. To prevent dirt and debris from falling
into the crankcase, wipe the area around the
cap with a clean cloth before removing the
4. Lightly oil the filter gasket with clean
engine oil. Install a new filter rated for your
engine. Screw in the filter by hand until the
gasket contacts the filter adapter (photo B).
Tighten the filter an additional 1⁄2 to 3⁄4 turn.
cap. If there is no dipstick, dab the oil with
B
a clean tip of the cloth to inspect the oil
(photo B).
C
3. If the engine includes a dipstick cap,
remove the dipstick and wipe it with a clean
cloth. To ensure an accurate reading, reinsert
the dipstick completely. Then, remove it
again and check the oil level. If the dipstick
cap is a screw-in type, ensure an accurate
reading by screwing it in all the way before
remov-ing it a second time to check the level.
The oil mark on the dipstick should be
between the lines shown on the dipstick
5. Add the appropriate quantity of oil (see
your owner’s manual). Then, run the engine
at idle and check for leaks.
6. After an oil change, dispose of oil and
soiled rags in accordance with local
environmental statutes (photo C). In many
areas, oil can be left at curbside with other
recyclables, provided it is sealed in a
recyclable container. Check the regulations
in your area.
(photo C). It should never be above the FULL
line or below the ADD line.
C
THE GUIDE TO SMALL ENGINES 5
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CHECKING SPARK PLUGS
Tools & materials:
Spark tester, spark plug
socket (sizes vary), socket
wrench, wire brush,
plug/point cleaner,
spark plug gauge.
Time required:
15 minutes.
A
necessary, use a spark plug gauge to adjust
the gap by gently bending the curved elec-
trode. When the gap is correct, the gauge will
drag slightly as you pull it through the gap.
3. If you see a spark jump the gap in the
tester, the ignition is functioning. The
absence of a visible spark indicates a problem
in the ignition system.
The electrodes on a spark plug must be
clean and sharp to produce the powerful
spark required for ignition. The more worn
or dirty a spark plug, the more voltage—and
the greater the tug on the rewind—required
to produce an adequate spark.
6. Reinstall the plug, taking care not to
Checking for spark miss
overtighten. Then, attach the spark plug lead.
A spark plug that is fouled or improperly
gapped may not allow sparks to jump the gap
between electrodes consistently. The spark
plug will fire erratically or may occasionally
fail to spark. Test for this problem—known as
spark “miss”—if your engine stumbles, with a
noticeable decrease in engine sound. Spark
miss can also cause the engine to emit black
smoke or a popping sound, as unburned fuel
exits with the exhaust and ignites inside the
muffler.
If you haven’t tuned your engine recently
and have to tug repeatedly on the rewind to
start the engine, a damaged spark plug may
be the culprit.
Checking ignition with
a spark tester
A spark tester offers an inexpensive, easy way
to diagnose ignition problems (see “Checking
for Spark Miss”).
Luckily, a spark plug is one of the easiest
engine components to repair and an
inexpensive one to replace. And your
standard socket set may already include the
most important tool—a spark plug socket.
If you find a problem, remove and inspect the
spark plug. Replace the spark plug if you find
evidence of wear or burning at the spark plug
tip. Spark plugs are inexpensive and a new
one may solve the problem.
1. With the spark plug screwed into the
cylinder head, attach the spark plug lead to
the long terminal of the spark tester. Attach
the tester’s alligator clip to the spark plug
(photo C).
1. Connect the spark plug lead to the long
terminal of your tester and ground the tester
to the engine with the tester’s alligator clip
(photo B).
Cleaning and inspecting
a spark plug
1. Disconnect the spark plug lead. Then,
clean the area around the spark plug to avoid
getting debris in the combustion chamber
when you remove the plug.
2. Start the engine and watch the tester’s
spark gap. You’ll recognize spark miss by the
uneven timing of the sparks in the tester.
2. Use the rewind or electric starter to crank
the engine, and look for a spark in the tester’s
window.
2. Remove the spark plug using a spark plug
socket.
3. Clean light deposits from the plug with a
wire brush and spray-on plug cleaner. Then,
use a sturdy knife if necessary to scrape off
tough deposits. NOTE: Never clean a spark
plug with a shot blaster or abrasives.
4. Inspect the spark plug for very stubborn
deposits, or for cracked porcelain or
electrodes that have been burned away. If any
of these conditions exists, replace the spark
plug.
5. Use a spark plug gauge to measure the
gap between the two electrodes (one straight,
one curved) at the tip of your spark plug
(photo A). Many small engines require a .030"
gap. Check the specifications for your model
with your power equipment dealer. If
B
C
6 THE GUIDE TO SMALL ENGINES
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SERVICING AIR CLEANERS
A properly maintained air cleaner is your engine’s first line of defense
against the destructive effects of dirt. When the air cleaner is in good
condition, it keeps airborne dirt particles from entering through the
carburetor. If the air cleaner is not maintained, dirt and dust will
gradually make their way into the engine. And don’t underestimate
dirt’s potential to cause damage. It can lead to a sharp drop in engine
power, or—worse—cause premature wear of critical engine
components.
Tools & materials:
Engine oil, screwdrivers, liquid detergent.
Time required:
30 minutes.
Many types of air cleaners are used in small engines. Most contain a
foam or pleated-paper element.
Pleats in a paper element that are discolored, bent or
water-damaged can no longer provide adequate air
to the carburetor. Replace the element when it
approaches this condition.
Dual-element air cleaners contain a pleated-paper element with a
foam pre-cleaner, offering two layers of protection. Discard the paper
element when you can no longer remove dirt from the pleats by
tapping the element on a hard, dry surface. You may be able to wash
and reuse the foam pre-cleaner. Foam elements can be cleaned with
hot water and liquid dish detergent that contains a grease-cutting
agent.
Servicing a pleated-paper or
dual-element air cleaner
Dual-element air cleaners come in a variety
of designs. Two of the most common are
shown here.
Single-element air cleaners should be serviced every 25 hours (or once
a season). In a dual-element system, the pre-cleaner should be cleaned
every 25 hours. The cartridge should be cleaned every 100 hours.
1. With the cover removed, separate the pre-
cleaner (if equipped) from the cartridge
(photo C).
2. Tap the cartridge gently on a flat surface
Pre-cleaner
Servicing a foam air cleaner
1. Loosen the screws or wing nuts that hold
the air cleaner assembly in place (photo A).
Disassemble.
to remove any loose dirt. Inspect the element
and replace it if it is heavily soiled, wet or
crushed.
Pleated-paper
element
3. Inspect the pre-cleaner, if equipped. Note
the mesh backing, designed to act as a barrier
between the oily pre-cleaner and the pleated-
paper element. Replace it when soiled or
worn.
2. Inspect the foam element. Replace it if it
is torn or shows signs of considerable wear.
4. Saturate the element with engine oil
(photo B). Then, squeeze it to spread the oil
throughout.
C
4. Look for oiling instructions on the pre-
cleaner (photo D). If directed, lubricate the
pre-cleaner with oil. NOTE: Not all foam pre-
cleaners should be oiled.
Pleated-paper
element
Don’t wait until your air
cleaner element looks like
this to replace it. If your
element has become
5. Inspect the rubbery sealing gasket
between the air cleaner and carburetor.
Replace it if it is worn.
Pre-cleaner
5. Clean the cartridge housing with a dry
cloth (photo E). Do not clean with solvents or
compressed air.
permanently discolored
or has begun to break
down or tear, extend the
life of your small engine
by installing a new one.
6. Reassemble and reinstall the air cleaner.
6. Reassemble the air cleaner. If the pre-
cleaner is the oiled type, take care to insert
the mesh toward the paper element so that
the paper is never exposed to the oil.
D
7. Reinstall, making sure that any tabs on
the cartridge are in their slots on the engine
housing. Gaps around the cartridge permit
unfiltered air and damaging dirt particles to
enter the engine.
A
B
E
THE GUIDE TO SMALL ENGINES 7
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*Refer to Briggs & Stratton Small Engine
Care & Repair for complete procedures.
TROUBLESHOOTING
If the engine won’t start
If the engine runs poorly
Ask this
question:
If the answer
is yes:
Ask this
question:
If the answer
is yes:
(Fuel line)
(Engine smokes)
Fill fuel tank; if engine
is still hot, wait until it
cools before filling tank.
Adjust the carburetor.*
Is the fuel mixture
too rich?
Is the fuel tank
empty?
Is the air filter
Replace the air cleaner.
Is the shut-off
valve closed?
Open fuel shut-off valve. plugged?
Empty tank, replace fuel
and check for leaks in
fuel tank cap.
Is the fuel diluted
with water?
(Engine overheats)
Is the engine dirty?
Clean the engine.*
Disconnect inlet screen
from engine and clean
using compressed air.
Do not use compressed
air near engine.*
Add oil to the engine.
NOTE: Never add oil to
the gasoline for a four-
stroke engine.*
Is the fuel line
or inlet screen
blocked?
Is the oil level low?
Are any shrouds or
cooling fins
missing or broken?
Is the fuel tank
cap clogged or
unvented?
Make sure cap is vented
and air holes are not
clogged.*
Install new parts as
needed.*
Is the fuel mixture
too lean?
(Carburetor)
Remove spark plug lead
and spark plug; pour
teaspoon of fuel directly
into cylinder; reinsert
spark plug and lead;
Adjust the carburetor.*
Replace the gasket.*
Is there a leaky
gasket?
Is the carburetor
blocked?
start engine; if it runs
shortly before quitting,
overhaul carburetor.*
Is the fuel tank
vent or fuel tank
screen plugged?
Clean the fuel tank vent
and fuel tank screen.*
Adjust float in fuel bowl,
if adjustable; make sure
choke isn’t set too high.*
Is the engine
flooded?
(Engine knocks)
Does the combust-
ion chamber contain
excess carbon?
Clean carbon from the
piston and head.*
(Ignition)
Remove spark plug;
clean contacts or
replace plug.
Is the spark plug
fouled?
Is the flywheel
loose?
Inspect the flywheel and
key; replace as needed.*
Is the spark plug
gap set incorrectly?
Remove spark plug;
reset gap.
(Spark plug misses
under load)
Is the spark plug
fouled?
Clean the spark plug.
Is the spark plug
lead faulty?
Test lead with spark
tester, then test engine.
Replace the spark plug
or adjust the spark
plug gap.
Is the spark plug
faulty or gap
incorrect?
Is the kill switch
shorted?
Repair or replace kill
switch.*
Are the breaker
points faulty?
Replace flywheel key,
then try to start engine;
if it still won’t start,
check ignition arma-
ture, wire connections
or points.*
Install a solid-state
ignition.*
Is the flywheel
key damaged?
Is the carburetor
set incorrectly?
Adjust the carburetor.
Is the valve
(Compression)
Perform compression
test. If test indicates
poor compression,
inspect valves, piston
and cylinder for damage
and repair as needed.*
Replace the valve spring.
spring weak?
Are the valves,
piston, cylinder
or connecting
rod damaged?
Adjust the valve
clearance to
recommended settings.
Is the valve
clearance set
incorrectly?
Printed in U.S.A.
© 2001 Briggs & Stratton Corporation
Form MS-6605-2/01
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