Briggs & Stratton 21000 Series Installation and operation manual

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Model Series
Covered in
This Manual
21000
21100
Operating & Maintenance Instructions
Model Type Code
Month Day Year
Note: General Model Series numbers noted above are inclusive of the specific model number found
on your engine. To get replacement parts or technical assistance in the future, write your
engine Model, Type, Code and date of purchase here.
TABLE OF CONTENTS
Safety 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Information 6. . . . . . . . . . . . . . . . . . . . . . . .
Oil 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel and Starting Information 8. . . . . . . . . . . . . . .
Starting and Stopping 9-10. . . . . . . . . . . . . . . . . . .
Maintenance 11-13. . . . . . . . . . . . . . . . . . . . . . . . .
Parts and Service & Storage 14. . . . . . . . . . . . . . .
Warranty Information 15. . . . . . . . . . . . . . . . . . . . .
WARNING
Briggs & Stratton does not approve or authorize the use of these engines
on 3-wheel All Terrain Vehicles (ATVs), motor bikes, scooters, aircraft
products or vehicles intended for use in competitive events. Use of these
engines in such applications could result in property damage, serious
injury (including paralysis), or even death.
Need assistance? Go to www.briggsandstratton.com
for detailed information regarding
Briggs & Stratton engines.
Or call, 1-800-233-3723, (U.S.A. and Canada)
to hear a menu of pre-recorded messages
offering engine maintenance information.
PRINTED IN U.S.A. Copyright 2004 by Briggs & Stratton Corporation FORM NO. 275064-2/04

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The Power That Works For You.
Look For Relevant Emissions Durability Period and
Air Index Information On Your Engine Emissions Label
Engines that are certified to meet the California Air Resources Board (CARB) Tier 2 Emission Standards must display information regard-
ing the Emissions Durability Period and the Air Index. Briggs & Stratton makes this information available to the consumer on our emission
labels and hang tags.
The Emissions Durability Period describes the number of hours of actual running time for which the engine is certified to be emissions
compliant, assuming proper maintenance in accordance with the Operating & Maintenance Instructions. The following categories are
used:
Moderate: Engine is certified to be emission compliant for 50 hours of actual engine running time.
Intermediate: Engine is certified to be emission compliant for 125 hours of actual engine running time.
Extended: Engine is certified to be emission compliant for 300 hours of actual engine running time.
For example, a typical consumer string trimmer is used 5 to 10 hours per year. Therefore, the Emissions Durability Period of an engine
with an moderate rating would equate to 5 to 6 years.
The Air Index is a calculated number describing the relative level of emissions for a specific engine family. The lower the Air Index,the
cleaner the engine. This information is displayed in graphical form on the emissions label or hang tag.
After July 1, 2000, Look For Emissions Compliance Period On
Engine Emissions Compliance Label
After July 1, 2000 certain Briggs & Stratton engines will be certified to meet the United States Environmental Protection Agency (USEPA)
Phase 2 Class IV emission standards. For Phase 2 Class IV certified engines, the Emissions Compliance Period referred to on the Emis-
sions Compliance label indicates the number of operating hours for which the engine has been shown to meet Federal emission require-
ments. For engines equal to or greater than 20 cc, and less than 50 cc displacement, Category C = 50 hours, B = 125 hours and A =
300 hours.
The displacement of Model Series 21000 engines is 34 cc, 21100 engines is 40 cc.
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BEFORE OPERATING ENGINE
•Read entire Operating & Maintenance Instructions AND
the instructions for the equipment this engine powers.*
•Failure to follow instructions could result in serious injury
or death.
THE OPERATING & MAINTENANCE INSTRUCTIONS
CONTAIN SAFETY INFORMATION TO
•Make you aware of hazards associated with engines
•Inform you of the risk of injury associated with those hazards, and
•Tell you how to avoid or reduce the risk of injury.
275064
The safety alert symbol ( ) is used to identify safety
information about hazards that can result in personal injury.
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.
DANGER indicates a hazard which, if not
avoided, will result in death or serious injury.
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.
CAUTION,when used without the alert symbol,
indicates a situation that could result in damage
to the engine.
WARNING
The engine exhaust from this
product contains chemicals known
to the State of California to cause
cancer, birth defects, or other
reproductive harm.
HAZARD SYMBOLS AND MEANINGS
Explosion
Toxic Fumes
Moving Parts
Shock
Hot Surface Kickback
Fire
THE INTERNATIONAL SYMBOLS USED
ON THE ENGINE OR
IN THIS MANUAL INCLUDE:
On Off
Read Owner’s
Manual
Stop Fuel
Full
Choke
Safety Alert Oil Primer
Open
Choke
*Briggs & Stratton does not necessarily know what equip-
ment this engine will power. For that reason, you should
carefully read and understand the operating instructions
for the equipment on which your engine is placed.

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SAFETY
Gasoline and its vapors are extremely
flammable and explosive.
Fire or explosion can cause severe burns
or death.
WARNING
WHEN ADDING FUEL
•Turn engine OFF and let engine cool at least 2
minutes before removing gas cap.
•Fill fuel tank outdoors or in well-ventilated area.
•Do not overfill fuel tank.
•Keep gasoline away from sparks, open flames,
pilot lights, heat, and other ignition sources.
•Check fuel lines, tank, cap, and fittings frequently
for cracks or leaks. Replace if necessary.
WHEN STARTING ENGINE
•Make sure spark plug, muffler, fuel cap and air
cleaner are in place.
•Do not crank engine with spark plug removed.
•If fuel spills, wait until it evaporates before starting
engine.
•If engine floods, set choke to OPEN/RUN position,
and crank until engine starts.
WHEN OPERATING EQUIPMENT
•Do not choke carburetor to stop engine.
WHEN TRANSPORTING EQUIPMENT
•Transport with fuel tank EMPTY.
WHEN STORING GASOLINE OR EQUIPMENT
WITH FUEL IN TANK
•Store away from furnaces, stoves, water heaters or
other appliances that have pilot light or other
ignition source because they can ignite gasoline
vapors.
Starting engine creates sparking.
Sparking can ignite nearby flammable
gases.
Explosion and fire could result.
WARNING
•If there is natural or LP gas leakage in area, do not
start engine.
•Do not use pressurized starting fluids because
vapors are flammable.
WARNING
•When starting engine, pull cord slowly until
resistance is felt, then pull rapidly.
•Direct coupled equipment components such as,
but not limited to, blades, impellors, pulleys,
sprockets, etc., must be securely attached.
Rapid retraction of starter cord (kickback) will
pull hand and arm toward engine faster than
you can let go.
Broken bones, fractures, bruises or sprains
could result.
WARNING
Rotating parts can contact or entangle
hands, feet, hair, clothing, or accessories.
Traumatic amputation or severe laceration
can result.
•Operate equipment with guards in place.
•Keep hands and feet away from rotating parts.
•Tie up long hair and remove jewelry.
•Do not wear loose-fitting clothing, dangling
drawstrings or items that could become caught.

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SAFETY
Engines give off carbon monoxide, an
odorless, colorless, poison gas.
Breathing carbon monoxide can cause
nausea, fainting or death.
WARNING
•Start and run engine outdoors.
•Do not start or run engine in enclosed area, even if
doors or windows are open.
WARNING
Running engines produce heat. Engine
parts, especially muffler, become extremely
hot.
Severe thermal burns can occur on contact.
Combustible debris, such as leaves, grass,
brush, etc. can catch fire.
•Allow muffler, engine cylinder and fins to cool
before touching.
•Remove accumulated combustibles from muffler
area and cylinder area.
•Install and maintain in working order a spark
arrester before using equipment on forest-covered,
grass-covered, brush-covered unimproved land.
The state of California requires this (Section 4442
of the California Public Resources Code). Other
states may have similar laws. Federal laws apply
on federal land.
WARNING
Unintentional sparking can result in fire or
electric shock.
Unintentional start-up can result in en-
tanglement, traumatic amputation, or lac-
eration.
BEFORE PERFORMING ADJUSTMENTS OR
REPAIRS
•Disconnect spark plug wire and keep it away from
spark plug.
WHEN TESTING FOR SPARK
•Use approved spark plug tester.
•Do not check for spark with spark plug removed.
ENGINE INFORMATION
TECHNICAL INFORMATION
POWER RATINGS: The power ratings for an individual engine
model are initially developed by starting with SAE (Society of Auto-
motive Engineers) code J1940 (Small Engine Power & Torque
Rating Procedure) (Revision 2002-05). Given both the wide array
of products on which our engines are placed, and the variety of en-
vironmental issues applicable to operating the equipment, it may
be that the engine you have purchased will not develop the rated
horsepower when used in a piece of power equipment (actual “on-
site” power). This difference is due to a variety of factors including,
but not limited to, the following: differences in altitude, tempera-
ture, barometric pressure, humidity, fuel, engine lubrication, maxi-
mum governed engine speed, individual engine to engine variabil-
ity, design of the particular piece of power equipment, the manner
in which the engine is operated, engine run-in to reduce friction
and clean out of combustion chambers, adjustments to the valves
and carburetor, and other factors. The power ratings may also be
adjusted based on comparisons to other similar engines utilized
in similar applications, and will therefore not necessarily match the
values derived using the foregoing codes.

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6
ENGINE INFORMATION
1. Carburetor
2. Stop switch
3. Rope handle
4. Fuel fill
5. Air cleaner
6. Choke
7. Spark plug
8. Fuel return hose
9. Fuel intake hose
10. Primer bulb
11. Engine Model Type Code
xxxxxx xxxx xxxxxxxx
12. Oil fill / dipstick
17
10
4
5
2
3
68
9
11
12
GENERAL INFORMATION
ENGINE MODEL
This is a single cylinder, air-cooled engine. It is a low emissions en-
gine.
In the state of California, Model Series 21000 and 21100 engines
are certified by the California Air Resources Board to meet emis-
sions standards for 50 hours. Such certification does not grant the
purchaser, owner or operator of this engine any additional warran-
ties with respect to the performance or operational life of this en-
gine. This engine is warranted solely according to the product and
emissions warranties stated elsewhere in this manual.
MODEL SERIES 21000
Bore 1.575 in. (40 mm). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stroke 1.065 in. (27 mm). . . . . . . . . . . . . . . . . . . . . . . . . . .
Displacement 2.074 cu. in. (34 cc). . . . . . . . . . . . . . . . . . .
MODEL SERIES 21100
Bore 1.575 in. (40 mm). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stroke 1.250 in. (31.75 mm). . . . . . . . . . . . . . . . . . . . . . . .
Displacement 2.44 cu. in. (40 cc). . . . . . . . . . . . . . . . . . . .
Note: Engine power will decrease 3-1/2% for each 1,000
feet (300 meters) above sea level and 1% for each 10°F
(5.6°C) above 77°F (25°C).
TUNE-UP SPECIFICATIONS
Armature air gap 0.010 – 0.014 in. (0.25 – 0.36 mm). . .
Spark plug gap 0.025 in. (0.64 mm). . . . . . . . . . . . . . . . . .
Valve clearance with valve springs installed and piston 1/4 in.
(6 mm) past top dead center (check when engine is cold).
See Repair Manual.
Intake 0.002 – 0.004 in. (0.05 – 0.10 mm). . . . . . . . . . . . .
Exhaust 0.002 – 0.004 in. (0.05 – 0.10 mm). . . . . . . . . . .

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OIL
275064
CAUTION:
This engine is shipped from Briggs & Stratton without
oil. Check oil level before starting engine. If you start the
engine without oil, the engine will be damaged beyond
repair and will not be covered under warranty. Do not
overfill.
OIL CAPACITY
Engine holds approximately 3 ounces (90 ml).
TYPE OF OIL TO USE
•Use a high quality detergent oil classified “For Service
SF, SG, SH, SJ” or higher, such as Briggs & Stratton
SAE 30, Part Number 100005 (20 oz) or Briggs &
Stratton Synthetic Oil, Part Number 100074.
•Do not use special additives.
Note: Synthetic oil meeting ILSAC GF-2, API certifica-
tion mark and API service symbol (shown at left) with “SJ/
CF ENERGY CONSERVING” or higher, is an acceptable
oil at all temperatures. Use of synthetic oil does not alter
required oil change intervals.
°F-20 0 20 40 60 80 100
°C-30 -20 -10 0 10 20 30 40
STARTING TEMPERATURE RANGE ANTICIPATED BEFORE NEXT OIL CHANGE
**
32
CAUTION: Air cooled engines run hotter than
automotive engines. The use of non-synthetic
multi-viscosity oils (5W-30, 10W-30, etc.) in
temperatures above 40°F (4°C) will result in higher
than normal oil consumption. When using a
multi-viscosity oil, check oil level more frequently.
* CAUTION: Synthetic oil must be used when
operating engine under 40°F (4°C) or engine
damage will occur.
** CAUTION: SAE 30 oil, if used below 50°F
(10°C), will result in hard starting and possible
engine bore damage due to inadequate
lubrication.
SAE Viscosity Grades
*
ADDING OIL
CAUTION: KEEP ENGINE LEVEL
Engine must be level, with oil fill facing up, to check
oil. If engine is not level, dipstick reading will not be
accurate. This will lead to possible over or under
filling causing damage to the engine.
•Check oil level before starting the engine.
•Check oil level before every use.
•Keep oil level at FULL.
•DO NOT overfill, use oil measure cup for filling.
•Add only 1 oz. – 0.5 oz. of oil at a time.
1 ounce
0.5 ounce
See also Changing Oil and
Checking Level under Maintenance Section.
OIL FILL
DIPSTICK
1. Place engine level. Re-
move dipstick. Using oil
measure cup pour oil
slowly. Do not overfill.
2. Tighten dipstick down.
3. To check oil level, remove
dipstick and wipe clean
with cloth. Tighten dip-
stick down. Remove &
check oil level.
4. Verify FULL level of oil by
presence of oil in hole on
dipstick, or by measure
line.
5. If needed, add 0.5 oz. oil
at a time to bring it to
FULL. Recheck level.
FULL
Note: Engine holds
approximately
3 oz. (90 ml)

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FUEL
TYPE OF FUEL TO USE
•Use clean, fresh, regular unleaded gasoline with a
minimum of 87 octane. Fresh fuel prevents gum from
forming in the fuel system or on essential carburetor
parts. Purchase fuel in quantity that can be used within
30 days.
•Do not use gasoline which contains Methanol.
•Do not mix oil with gasoline.
•For engine protection use Briggs & Stratton Fuel
Stabilizer available from your Authorized Briggs &
Stratton Dealer (P/N 5041 or single use pouch).
•This engine is certified to operate on gasoline. Exhaust
Emission Control System: EM (Engine Modifications).
CAUTION: Some fuels, called oxygenated or
reformulated gasoline, are gasoline blended with
alcohols or ethers. Excessive amounts of these
blends can damage the fuel system or cause
performance problems. If any undesirable operating
symptoms occur, use gasoline with a lower percent-
age of alcohol or ether.
ADDING FUEL
WARNING
Fuel Fill
1. Tilt engine at angle shown to properly fill fuel
tank.
2. Remove cap, and add fuel until level is
approximately 1” below top of fuel tank neck.
Be careful not to overfill.
3. Replace cap before starting.
•Fill fuel tank outdoors or in well-ventilated area, away
from sparks, open flames, pilot lights, heat, and other
ignition sources.
•If fuel spills, wait until it evaporates before starting
engine.
•Turn engine OFF and let engine cool at least 2 minutes
before removing gas cap.

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STARTING
If you are starting your engine for the
FIRST time, follow the steps outlined
under Starting A New Engine.
CAUTION:
This engine is shipped from Briggs & Stratton
without oil. Check oil level before starting engine.
If you start the engine without oil, the engine will be
damaged beyond repair and will not be covered
under warranty.
STARTING A NEW ENGINE
Add oil and fuel as instructed in this manual prior to
attempting to start engine. (See Oil and Fuel)
1. Set unit on flat surface, push primer bulb 15 times.
2. Move red choke lever to the FULL CHOKE
position.
TYPICAL
THROTTLE
TRIGGER
3. Squeeze throttle trigger and pull starter handle
sharply until engine runs.
4. Wait a maximum of 10 seconds, then move choke
lever to HALF CHOKE position.
5. Run the engine at HALF CHOKE for 20 seconds or
until unit accelerates smoothly. Move CHOKE to
OFF position.
STARTING AND OPERATING TIPS
♦After engine has
started, let it warm up
several seconds to
several minutes, de-
pending on outside
temperature.
♦For maximum perfor-
mance and life, oper-
ate engine with choke
in OFF position.
♦Use fresh fuel.
(See Fuel.)
♦Use correct type of oil
for expected starting
temperature. (See
Oil.)
♦Periodically remove
debris buildup from
blower housing open-
ings.
WARNING
Rotating parts can contact or entangle hands,
feet, hair, clothing, or accessories.
Traumatic amputation or severe laceration can
result.
•Operate equipment with guards in place.
•Keep hands and feet away from rotating parts.
WARNING
•Do not use pressurized starting fluids.
•Vapors are flammable.
FULL CHOKE
POSITION
6. Wait a minimum of 20 seconds, then release
throttle trigger.
OFF
POSITION
Choke
Lever Primer Bulb
HALF CHOKE
POSITION

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10
STARTING AND STOPPING
Follow steps under TO START ENGINE, with the
exception of step 4. Do not squeeze throttle trigger.
TYPICAL
THROTTLE
TRIGGER
CAUTION:
Operating engine at an excessive speed without
proper engine loading will cause damage.
Do not operate a string trimmer with a line shorter
than 10” in diameter for extended periods.
TO START A WARM ENGINE
If you are starting your engine for the
FIRST time, follow the steps outlined
under Starting A New Engine.
CAUTION:
This engine is shipped from Briggs & Stratton
without oil. Check oil level before starting engine.
If you start the engine without oil, the engine will be
damaged beyond repair and will not be covered
under warranty.
TO START ENGINE
FULL CHOKE
POSITION
OFF
POSITION
Choke
Lever Primer Bulb
HALF CHOKE
POSITION
FULL
1. Check oil level. Oil should be
at FULL, if not add oil.
(See Oil)
2. Set unit on flat surface, push
primer bulb 8times.
3. Move red choke lever to FULL choke position.
4. Squeeze throttle trigger and
5. Pull starter handle sharply until engine runs.
6. Wait a maximum of 10 seconds, then move
choke lever to HALF CHOKE position.
7. Run the engine at HALF CHOKE for 20 seconds
or until unit accelerates smoothly. Move
CHOKE to OFF position.
8. Wait a minimum of 20 seconds, then release
throttle trigger.
TO STOP ENGINE
Depress stop switch to stop engine.
•Do not choke carburetor to stop engine.
WARNING
Gasoline and its vapors are extremely flammable
and explosive.
Fire or explosion can cause severe burns or death.