Briggs & Stratton 272147 Operating instructions

®
®
BRIGGS & STRATTON CORPORATION
Milwaukee, WI 53201
Part No. 275429-1/04 Printed in U.S.A.
www.briggsandstratton.com
272147 - Single Cylinder OHV Air-Cooled Engines
272144 - Vanguard™ Twin Cylinder OHV Air-Cooled Engines
275429 - Vanguard™ Twin Cylinder OHV Liquid-Cooled Engines
MS-0750 - Vanguard™ 3-Cylinder OHV Liquid-Cooled Gasoline Engines
MS-1055 - Vanguard™ 3-Cylinder OHV Liquid-Cooled Diesel Engines
Quality Starts With A
Master Service Technician
Other Briggs & Stratton
Commercial Power Repair Manuals:
Vanguard Twin Cylinder
OHV Liquid-Cooled Engines
Briggs & Stratton VANGUARD™ TWIN CYLINDER OHV LIQUID-COOLED ENGINES Part No. 275429-1/04
REPAIR MANUAL
™
275429_2LC_.1875_Spine 3/29/06 11:11 AM Page 1
For Briggs & Stratton Discount Parts Call 606-678-9623 or 606-561-4983
www.mymowerparts.com

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
MODEL 473100
2 CYLINDER LIQUID COOLED ENGINE
COMMERCIAL POWER
MANUAL NUMBER: 275429

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
SAFETY INFORMATION
The Briggs & Stratton engine is made of the finest
material in a state-of-the-art manufacturing facility.
Please understand that Briggs & Stratton sells engines
to original equipment manufacturers. It also sells to
others in the distribution chain who may sell to the
ultimate consumer, an equipment manufacturer, another
distributor or a dealer. As a result, Briggs & Stratton does
not necessarily know the application on which the engine
will be placed. For that reason, carefully read and
understand the operating instructions of the equipment
before you repair or operate.
You should also understand that there are equipment
applications for which Briggs & Stratton does not
approve the useof its engines. Briggs & Stratton engines
are not to be used on vehicles with less than 4 wheels.
This includes motor bikes, aircraft products and all
terrain vehicles. Moreover, Briggs & Stratton does not
approve of its engines being used in competitive events.
FOR THAT REASON, BRIGGS & STRATTON
ENGINES ARE NOT AUTHORIZED FOR ANY OF
THESE APPLICATIONS. Failure to follow this warning
could result in death, serious injury (including paralysis)
or property damage.
IN THE INTEREST OF SAFETY
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 this signal word is used without the
alert symbol, it indicates a situation that could result in
damage to the engine.
• Prior to work, read and understand the section(s) of
this manual that pertain to the job. Follow all safety
warnings.
• Wear suitable eye protection.
• Prevent accedental starting by removing spark plug
wire from spark plug when servicing engine or
equipment. Disconnect negative battery terminal if
equipped with electric starting system.
• Periodically clean engine. Keep governor parts free
of dirt, grass and other debris which can affect
engine speed.
• Always use fresh gasoline. Stale fuel can gum
carburetor and cause leakage.
• Check fuel lines and fittings frequently for cracks or
leaks and replace if necessary.

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Table Of Contents
Page 1
MODEL 473100
2 CYLINDER LIQUID COOLED ENGINE
COMMERCIAL POWER .........................................1
SAFETY INFORMATION .......................................2
IN THE INTEREST OF SAFETY...................... 2
SECTION 1
GENERAL INFORMATION .................................... 3
ENGINE IDENTIFICATION ..............................4
MAINTENANCE SCHEDULE ...........................5
FUEL AND OIL RECOMENDATIONS ..............6
CHANGING OIL AND OIL FILTER................... 7
CHANGE COOLANT ........................................7
CLEANING DEBRIS .........................................8
ADJUST FAN BELT .........................................8
AIR CLEANER MAINTENANCE ......................8
REPLACE SPARK PLUG .................................9
SECTION 2
TROUBLESHOOTING .........................................11
GENERAL INFORMATION ............................11
WILL NOT START ..........................................11
STARTER CURRENT DRAW TEST ..............12
NO LOAD
STARTER CURRENT DRAW TEST ..............13
CHECK CARBURETION ................................16
FUEL SHUT-OFF SOLENOID ........................16
FUEL PUMP - GENERAL INFORMATION ....17
CYLINDER BALANCE TEST .........................18
CYLINDER LEAKDOWN TEST ......................19
CHECKING COOLING SYSTEM ...................21
CHECK OIL PRESSURE SWITCH ................22
CHECK OIL PRESSURE ...............................23
CHARGING SYSTEM .....................................23
BATTERY INFORMATION .............................25
EQUIPMENT
AFFECTING ENGINE OPERATION ...............26
SECTION 3
ENGINE DISASSEMBLY ......................................27
GENERAL INFORMATION .............................27
REMOVE MUFFLER .......................................27
REMOVE RADIATOR .....................................27
DISCONNECT FUEL LINES ...........................28
REMOVE FAN ASSEMBLY ............................28
REMOVE CARBURETOR ..............................29
REMOVE STARTER .......................................30
REMOVE INTAKE MANIFOLD .......................31
REMOVE ALTERNATOR ...............................32
REMOVE CYLINDER HEADS ........................32
REMOVE CRANKCASE COVER ...................33
REMOVE CAMSHAFT ....................................34
REMOVE PISTONS, RODS, CRANKSHAFT .34
SECTION 4
ENGINE OVERHAUL ............................................35
CHECK CYLINDER ........................................35
BEARINGS ......................................................37
CRANKSHAFT ................................................38
PISTON, RINGS AND CONNECTING ROD
DISASSEMBLY AND INSPECTION ...............38
CYLINDER HEAD
INSPECTION AND REPAIR ...........................41
OIL PUMP .......................................................44
REPLACING WATER PUMP SEAL ................45
REPLACING STARTER SOLENOID ..............46

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Table Of Contents
Page 2
REPLACING PINION GEAR ASSEMBLY ......47
CARBURETOR INSPECTION AND REPAIR .51
SECTION 5
ENGINE ASSEMBLY ............................................57
INSTALL CRANKSHAFT ................................57
ASSEMBLE
PISTON AND CONNECTING ROD ................57
ASSEMBLE PISTON RINGS TO PISTON .....57
INSTALL
PISTON AND CONNECTING ROD ................58
INSTALL CAMSHAFT ....................................59
INSTALL GOVERNOR GEAR ........................59
INSTALL CRANKCASE COVER ....................59
INSTALL STARTER .......................................60
INSTALL ALTERNATOR ................................60
INSTALL FLYWHEEL .....................................61
INSTALL CYLINDER HEADS .........................61
INSTALL ROCKER ARMS .............................61
ADJUST VALVE CLEARANCE ......................62
INSTALL ARMATURES ..................................62
INSTALL FAN ASSEMBLY .............................63
INSTALL INTAKE MANIFOLD ........................64
INSTALL CARBURETOR AND INTAKE ELBOW
ASSEMBLY ....................................................64
ADJUST GOVERNOR ....................................66
INSTALL MUFFLER .......................................66
INSTALL RADIATOR ......................................67
INSTALL AIR CLEANER ASSEMBLY ............67
SECTION 6
FINAL ADJUSTMENTS AND
SPECIFICATIONS ................................................ 71
GENERAL INFORMATION ............................ 71
REMOTE GOVERNOR CONTROLS.............. 71
CARBURETOR ADJUSTMENT ..................... 72
MODEL 473100 SPECIFICATIONS ............... 75
ENGINE HARNESS ....................................... 77

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 3
SECTION 1 GENERAL INFORMATION
BRIGGS & STRATTON NUMERICAL IDENTIFICATION SYSTEM
This chart explains the unique Briggs & Stratton numerical model designation system. It is possible to determine most of the important
mechanical features of the engine by merely knowing the model number. Here is how it works:
• A. The first one or two digits indicate the approximate CUBIC INCH DISPLACEMENT.
• B. The first digit after the displacement indicates the BASIC DESIGN SERIES, relating to cylinder construction, ignition, general
configuration, etc.
• C. The second digit after the displacement indicates ORIENTATION OF CRANKSHAFT.
• D. The third digit after the displacement indicates TYPE OF BEARINGS, and whether or not the engine is equipped with
REDUCTION GEAR or AUXILIARY DRIVE.
• E. The last digit indicates the TYPE OF STARTER.
BRIGGS & STRATTON MODEL NUMBERING SYSTEM
First Digit
After Displalcement Second Digit
After Displalcement Third Digit
After Displalcement Fourth Digit
After Displalcement
ABCDE
Cubic Inch
Displacement Basic
Design Series PTO Bearing
Reduction Gear,
Auxiliary Drive,
Lubrication
Crankshaft
Orientation Type of
Starter
Plain Bearing/DU
Non-Flange Mount
Plain Bearing
Flange Mount
Sleeve Bearing
Flange Mounting
Splash Lube
Ball Bearing
Flange Mounting
Splash Lube
Ball Bearing
Flange Mounting
Pressure Lubrication
Plain Bearing
Gear Reduction
(6-1) CCW Rotation
Flange Mounting
Plain Bearing
Gear Reduction
(2-1) CCW Rotation
Plain Bearing
Pressure Lubrication
Plain Bearing
AuxiliaryDrive(PTO)
Perpendicular to
Crankshaft
Plain Bearing
AuxiliaryDrive(PTO)
Parallel to
Crankshaft
Plain Bearing
Pressure Lubrication
Without Oil Filter
0 -
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
A -
Example - To Identify Model 303447:
30
30 Cubic Inch 3
Design Series 3 4
Horizantal Shaft
0
1
2
3
4
5
6
7
8
9
A to Z
6
8
9
10
11
12
13
16
18
19
20
21
22
23
24
25
28
29
30
31
32
35
38
40
42
43
44
46
47
52
54
58
0 to 4 - Horizantal Shaft
5 to 9 - Verticle Shaft
A to G - Horizantal Shaft
H to z - Verticle Shaft
Without Starter
Rope Starter
Rewind Starter
Electric Starter Only
110 or 230 Volt Gear
Drive
Electric Starter/110
or 230 Volt Gear
Drive with Alternator
Electric Starter Only
12 or 24 Volt Gear
Drive
Alternator Only
Electric Starter 12 or
24 Volt Gear Drive
with Alternator
Verticle Pull Starter
or Side Pull Starter
Mechanical Starter
Electric Starter 12 or
24 Volt Gear Drive
with Alternator and
Inverter
0 -
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
A -
4
Horizantal Shaft
Flange Mounting
Pressure Lubrication
7
Electric Starter
12 or 24 Volt Gear Drive
with Alternator
TYPE 1234-01 The type number identifies the engine mechanical parts, color of paint, decals, goverened speed and original Equipment Manufacturer.
Code 01061201 The code is the manufacturing dat and is read as follows:
Year
01 MONTH
06 DAY
12 ASSEMBLY LINE AND MANUFACTURING PLANT

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 4
ENGINE IDENTIFICATION
Fig. 1
Oil Fill Cap
Dipstick
Spark Plug
12V Electric Starter
Oil Drain Plug
Fan Belt (If Equipped)
Fuel Filter
Radiator Drain Plug (If Equipped)
Radiator Screen & Handle (If Equipped)
Radiator & Radiator Cap (If Equipped)
Air Cleaner (If Equipped)
Fuel Pump
Muffler (If Equipped)
Choke Control
Throttle Control (2 Possible Locations)
Radiator Reservoir (If Equipped)
Oil Filter
Oil Drip Tray (Igf Equipped)
Oil Pressure Switch
Engine Model Label
MODEL TYPE CODE
xxxxxx xxxx xx xxxxxxxx

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 5
Change oil after first 50 hours of use, then every
100 hours or every season. Change oil every 50
hours when operating the engine under heavy load orin
high temperatures.
Clean more often under dusty conditions or when
airborne debris is present. Replace air cleaner
parts, if very dirty.
If an extended life coolant is used, interval may be
increased to once every 3000 hours.
MAINTENANCE SCHEDULE
Daily 50 Hours 100 Hours 250 Hours 600 Hours Yearly
Check Oil
Level X
Check For Oil
Leaks X
Change Oil X*
Change Oil
Filter X*
Check
Coolant
Change
Coolant XX***
Check Fan
Belt X
Clean Air
Filter X**
Replace Air
Filter X**
Check Valve
Clearance X
Check
Battery
Electrolyte
X
Change
Spark Plugs X
Change Fuel
Filter X
Clean Spark
arrestor X
*
**
***

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 6
FUEL AND OIL RECOMENDATIONS
Gasoline
Use clean, fresh, unleaded gasoline. Leaded gasoline
may be used if unleaded is not available. A minimum of
85 octane is recommended. The use of unleaded
gasoline results in fewer combustion deposits and longer
valve life.
We do not recommend the use of gasoline that contains
alcohol, such as gasohol. However, if used, it must not
contain more than 10 percent Ethanol and must be
removed from the engine during storage. Do not use
gasoline that contains Methanol.
Only purchase a 30-day supply of gasoline. Fresh
gasoline minimizes gum deposits and also will ensure
fuel volatility tailored for the season in which the engine
will be operated.
NOTE: The use of a fuel additive, such as
Briggs & Stratton Gasoline Additive (#5041) or
equivalent, will minimize the formation of fuel
gum deposits during storage. Such an additive
may be added to the fuel tank or storage
container.
Lubrication
Oil has four purposes. It cools, cleans, seals and
lubricates. During normal operation, small particles of
metal from the cylinder walls, pistons, bearings and
combustion deposits will gradually contaminate the oil.
Dust particles from the air also contaminate the oil
forming an abrasive mixture which can cause wear to all
of the internal moving parts of the engine, if the oil is not
changed regularly. Fresh oil also assists in cooling. Old
oil gradually becomes thick and loses its cooling ability
as well as its lubricating qualities.
Oil Recommendations
Use a high quality detergent oil classified “For Service
SF, SG, SH, SJ” or higher. Briggs & Stratton strongly
recommends the use of synthetic oil such as Briggs &
Stratton (#100074) or equivalent. If synthetic oil is not
available, Briggs & Stratton non-synthetic 30 weight oil
(#100005 or #100028) is an acceptable substitute. No
special additives should be used with recommended oils.
Do not mix oil with gasoline.
SAE Viscosity Grades
CAUTION: The use of non-synthetic multi-
viscosity oils (5W-30, 10W-30, etc.) in
temperatures above 405°F (45°C) will result in
higher than normal oil consumption. When using
a multi-viscosity oil, check oil level more
frequently.
SAE 30 oil, if used below 405°F (45°C), will
result in hard starting and possible engine bore
damage due to inadequate lubrication.
Lubrication System
Briggs & Stratton Vanguard™ liquid cooled OHV V-
Twins use a full pressure lubrication system with an oil
filter. The gear driven oil pump draws oil from a screened
oil pickup and pumps the oil through the oil filter.
The filtered oil flows through oil galleries in the cylinder
and crankcase cover and is distributed through the
crankshaft to the main bearings and connecting rod
bearings. Engine oil pressure will vary with oil viscosity,
ambient air temperature differences, operating
temperatures and engine load. Follow the oil
recommendation shown above.
Oil Pressure - @ 705° F (215° C): 10 ~ 50 psi
(0.7 ~ 3.5 Bar)
A pressure relief valve limits the maximum oil pressure in
the system.
The engine may be equipped with an oil pressure switch
which may be used to activate a warning device if oil
pressure drops below approximately 8 psi (.55 Bar). The
warning device is supplied by the equipment
manufacturer.

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 7
CHANGING OIL AND OIL FILTER
Change oil and filter after first fifty (50) hours of
operation.
Thereafter, change oil and filter every one hundred (100)
hours of operation. Change oil more often if engine is
operated in dirty or dusty conditions or if engine is
operated under heavy loads or in high ambient air
temperatures.
Oil Capacity: Approximately 87 oz. (2.6 liters) with filter.
Place equipment so that engine is level.
1. Remove oil drain plug and drain oil while engine is
still warm.
2. Install and torque drain plug to 20 ft. lbs. (27 Nm).
3. Remove oil filter and clean mounting surface.
4. Lightly oil new filter gasket with engine oil.
5. Screw filter on by hand until gasket contacts oil
filter adapter. Tighten 1/2 to 3/4 turn more.
6. Clean area around oil fill cap, then remove oil fill
cap and add 67 ounces (2 liters) of oil.
7. Start and run engine at idle for 60 seconds. Then,
shut engine off and wait 60 seconds.
8. Add more oil slowly to bring oil level to FULL mark
on dipstick. Do Not Overfill.
NOTE: Overfilling can cause a smoking or
overheating condition due oil foaming.
Fig. 2
9. Replace oil fill cap and dipstick.
10. Start and run engine to check for oil leaks.
CHANGE COOLANT
Coolant should be replaced every year, unless an
approved extended life coolant is used. Then replace
every 3000 hours.
NOTE: A 50/50 mixture of phosphate-free
antifreeze and tap water is required for proper
heat dissipation, rust resistance and lubrication.
CAUTION: Used coolant is a hazardous waste
product. Dispose of used coolant properly.
Check with your local authorities, service center,
or dealer for safe disposal/recycling facilities.
1. Remove drain plug. As coolant is running out,
open radiator cap to allow any trapped coolant to
drain. Replace drain plug.
2. Remove reservoir bottle, drain it and reinstall.
3. Fill radiator to bottom of filler neck and between
FULL and LOW in reservoir. Replace radiator cap.
4. Start and run engine for 30 seconds.
5. Shut engine off and allow it to cool. Recheck
coolant levels in radiator and reservoir.
6. Coolant level in reservoir bottle should be
between FULL and LOW when engine is cold.
Oil Filter
OIL DRAIN PLUG
OIL FILL
DIP STICK FULL

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 8
Normal coolant temperature gauge (if equipped) should
read between 175° and 195° F (80° and 90° C) when
engine is running.
If coolant temperature rises above 220° F (105° C), the
temperature light (if equipped) will illuminate. Idle engine
down for a while. Then stop engine. Once engine is
cooled, check coolant level, fan belt tension and clogged
radiator fins.
CLEANING DEBRIS
Daily or before every use, clean accumulated debris
from engine. Keep linkage, springs and controls clean.
Keep area around and behind muffler free of any
combustible debris.
Use the handle on the radiator screen to lift off for
cleaning. Clean screen thoroughly and clean radiator
fins.
Do not use water to clean engine parts. Water could
contaminate fuel system. Low pressure compressed air
may be used. Be careful not to damage radiator fins.
CAUTION: Engine parts should be kept clean
to reduce the risk of overheating and ignition of
accumulated debris
Fig. 3
ADJUST FAN BELT
• Check condition of fan belt.
• Replace if damaged or worn.
To Adjust Fan Belt Tension
1. Loosen bolt and bolt .
2. Fit torque wrench in the square hole located in the
bracket.
3. Apply 115 in. lbs. of torque in the direction of the
arrow.
4. While belt is being tensioned per step 3, torque
bolt to 125 in. lbs. (14 Nm). Torque bolt to
110 in. lbs. (12 Nm).
Fig. 4
AIR CLEANER MAINTENANCE
WARNING: Never operate engine with air
cleaner assembly or air cleaner cartridge
removed.
A properly serviced air cleaner protects internal parts of
the engine from dirt and dust particles in the air. If air
cleaner instructions are not carefully followed, dirt and
dust which should be collected in the cleaner will be
drawn into the engine. These particles are highly
abrasive and will cause the piston rings and cylinder
RADIATOR
CLEAN DEBRIS
CLEAN
HANDLE
DEBRIS
TORQUE
WRENCH
TORQUE
WRENCH
SQUARE
TORQUE
HOLE
FAN BELT
FAN BELT

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 9
bore to wear quickly. As the rings and cylinder bore
become worn, these abrasive particles enter the
crankcase and contaminate the oil, forming an abrasive
mixture which will cause wear on all of the internal
moving parts.
Clean cartridge every 100 hours. To clean cartridge,
gently tap on end with handle of screwdriver. Replace
cartridge every 600 hours. Clean and replace more often
under dusty conditions. Replace if very dirty or any
damage occurs to cartridge.
NOTE: Do not use pressurized air or solvents to
clean cartridge. Pressurized air can damage
cartridge; solvents will dissolve cartridge.
1. Unlock clamps and remove cover .
2. Remove cartridge from air cleaner body.
3. Carefully clean out air cleaner cover.
4. Install cartridge in body.
5. Install cover and lock clamps with rubber valve
down.
Fig.5
REPLACE SPARK PLUG
Replace spark plugs every year. Replace spark plugs if
electrodes are burned away, or the porcelain is cracked.
Set spark plug gap at .020” (.51 mm). Torque spark
plugs to 180 in. lbs. (20.0 Nm).
NOTE: Do not blast clean spark plugs. Spark
plugs should be cleaned by scraping or hand
wire brushing and washing in a commercial
solvent.
Fig. 6
B&S to Champion*
Plug Type B&S Champion*
Resistor Plug 491055 RC12YC
Resistor Plug 496018 RC14YC
Champion and the Bow Tie are trademarks of Federal-Mogul Ignition
Co. Used under license.
*

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 1 - General Information
Page 10

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 11
SECTION 2
TROUBLESHOOTING
GENERAL INFORMATION
Most complaints concerning engine operation can be
classified as one or a combination of the following:
1. Will not start
2. Hard Starting
3. Lack of power
4. Runs Rough
5. Vibration
6. Overheating
7. High Oil Consumption
NOTE: What appears to be an engine
malfunction may be a fault of the powered
equipment rather than the engine. If equipment
is suspect, see Equipment Affecting Engine
Operation.
WILL NOT START
Engine Will Not Turn Over
1. Make sure that safety equipment installed by the
Original Equipment Manufacturer (OEM) is
functioning properly and is not preventing the
engine from cranking. Remove any parasitic load
on engine (drive unit disengaged).
2. Make sure battery cables and solenoid
connections are clean and tight.
3. Check battery voltage from positive battery
terminal to battery terminal on solenoid.
Voltage must not be below 11.7 volts.
Check Starter
A jumper wire is required for the next test.
1. Disconnect wire at tab terminal on solenoid.
2. Attach one end of jumper wire to positive terminal
on battery. Then, make contact to tab terminal
on solenoid, Fig. 7.
3. If starter cranks, there is a problem with the key
switch or wiring.
Fig. 7
4. If starter does not crank, remove jumper wire from
battery and attach to battery terminal on
solenoid.
5. With other end of jumper wire, make contact to the
field terminal on solenoid, Fig. 8.
Fig. 8
6. If starter turns over, the solenoid is defective.
Replace solenoid.
If starter does not turn over, the starter motor is
defective. Replace starter motor.
Engine Turns Over Slowly
If engine turns over slowly, but will not start, first refer to
Will Not Start, steps 1 - 3. Then perform a starter current
draw test.

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 12
STARTER CURRENT DRAW TEST
IMPORTANT: When making the starter current draw
test make sure that all parasitic load is removed from the
engine and that engine has the correct viscosity oil.
Engine temperature should be at least 70°F (21°C).
Make sure battery and solenoid connections are clean
and tight.
NOTE: Battery voltage must not be below 11.7
volts.
Test Equipment
The following equipment is required to test current draw
of starter, Fig. 9.
Fig. 9
1. Digital multi-meter, Tool #19464.
2. DC shunt, Tool #19468.
3. Two battery cables with alligator clips.
4. One jumper wire with alligator clips.
5. A fully charged 12 volt battery.
Testing Starter
NOTE: To prevent engine from starting, remove
spark plug wires from spark plugs and ground
ignition using two Ignition Testers, Tool #19368.
Leave spark plugs installed.
The starter current draw test will be performed with the
meter in the 300mV position.
The DC Shunt must be installed on the negative (-)
terminal of the battery, Fig. 10.
Fig. 10
1. Attach RED meter test lead to RED post
terminal on shunt.
2. Attach BLACK meter test lead to BLACK post
terminal on shunt.
3. Activate starter.
a. Allow 3 seconds for meter reading to stabilize.
4. Current draw should not exceed 80 amps DC.
If amperage draw exceeds specification, remove starter
from engine and perform No Load starter current draw
test.
19464
19468
BATTERY
CABLES
JUMPER WIRES
3000mV
ATTACH NEGATIVE
BATTERY CABLE

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 13
NO LOAD STARTER CURRENT DRAW
TEST
Remove starter motor.
To hold starter securely while testing, clamp starter
mounting bracket in a vise. DO NOT clamp starter
housing in a vise or field windings or magnets may be
damaged.
Testing Starter (No Load)
The No Load starter current draw test will be performed
with the meter in the 300mV position.
The DC Shunt must be installed on the negative (-)
terminal of the battery, Fig. 11.
Fig. 11
1. Attach RED meter test lead to RED post
terminal on shunt.
2. Attach BLACK meter test lead to BLACK post
terminal on shunt.
3. Attach negative battery cable to a good
ground such as drive housing.
4. Attach positive battery cable to battery
terminal on solenoid.
5. Attach one end of jumper wire to solenoid tab
terminal, Fig. 11.
6. Activate starter by contacting positive battery
terminal with other end of jumper wire , Fig. 11.
a. Allow 3 seconds for meter reading to stabilize.
7. Current draw should not exceed 50 amps DC.
If amperage draw exceeds specification, replace
starter.
Hard Starting
Make sure the oil level is correct.
This engine is equipped with a “Low Oil Pressure
Sensor” and will not start if the oil level is too low.
Make sure drive unit is disengaged.
A loose drive belt like a loose blade can cause a
backlash effect, which will counteract engine cranking
effort.
NOTE: Magnetron® ignition system requires a
minimum of 350 RPM before it will produce a
spark.
Systematic Check
If the engine is hard starting or will not start and the
cause of malfunction is not readily apparent, perform a
systematic check in the following order:
1. Ignition
2. Carburetion
3. Compression
This check-up, performed in a systematic manner, can
usually be done in a matter of minutes. It is the quickest
and surest method of determining the cause of failure.
ATTACH NEGATIVE
BATTERY CABLE

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 14
Check Ignition (With Engine Starter)
With spark plugs installed, attach a #19368 ignition tester
to each spark plug lead and ground the other end of the
tester as shown in Fig.12. Activate the electric starter. If
spark jumps the tester gaps, you may assume the
ignition system is functioning satisfactorily.
Fig. 12
NOTE: Engines equipped with Magnetron®
ignition system will still display spark at tester
with a partially or fully sheared flywheel key. A
partially sheared flywheel key will affect ignition
timing and engine performance.
If spark does not occur look for:
1. Improperly operating interlock system
2. Shorted equipment stop switch wire
3. Two closed diodes in ground wire harness (see:
Troubleshooting Ground Wire Harness)
4. Incorrect armature air gap
5. Armature failure
Check Ignition (Engine Running)
If engine runs but misses during operation, a quick check
to determine if ignition is or is not at fault can be made by
installing Tool #19368 tester between the spark plug lead
and each spark plug, Fig.13. A spark miss will be readily
apparent when the engine is running. If spark is good but
engine misses, check for a fouled spark plug.
Fig. 13
Check Ignition (Fouled Plug or Other Causes)
To check for a fouled spark plug or a non-functioning
cylinder, attach Tool #19368 tester between the spark
plug lead and each spark plug. With engine running at
top no load speed, ground one spark plug, Fig. 14. The
engine should continue to run on the other cylinder.
Repeat this test with the other cylinder. If the engine will
not continue to run when making this test, the cylinder
that is NOT grounded is not functioning and/or the spark
plug is fouled. Install a new spark plug before
proceeding. When replacing spark plugs always use
Briggs & Stratton #491055 or #496018.

VanguardTM Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 15
Fig. 14
If miss continues:
The problem may be carburetion or compression related.
See Check Carburetion and/or Cylinder Balance Test
and Cylinder Leakdown Test.
Troubleshooting Ground Wire Harness
The ground wire harness contains two diodes. If a diode
fails “open,” the cylinder with the open diode will continue
to run when the equipment key switch is turned off. If a
diode fails “short,” the cylinder with the shorted diode will
not run (no spark).
Refer to Failure Diagnosis Table for symptoms.
Testing Ground Wire Harness
The Digital Multimeter, Tool #19464 is recommended to
test the ground wires. The following test will be made
with the meter in the “Diode Test Position”.
Fig. 15
In the Diode Test position, the meter will display the
forward voltage drop across the diode(s). If the voltage
drop is less than 0.7 volts, the meter will “Beep” once as
well as display the voltage drop. A continuous tone
indicates continuity (shorted diode). An incomplete
circuit (open diode) will be displayed as “OL.”
1. Insert RED test lead into receptacle in meter.
2. Insert BLACK test lead into receptacle in meter.
3. Rotate selector to (Diode Test) position.
4. Insert RED test lead into ground wire terminal
(brown wire) receptacle in engine harness,
Fig. 16. Leave attached for remainder of test.
5. Touch BLACK test lead probe to ground wire tab
terminal on ignition coil for #2 cylinder.
DIODE FAILURE DIAGNOSTIC TABLE
Ground Wire Harness
DiodeDiode
OFF ON
Equipment
Switch
SWITCH ON SWITCH OFF CAUSE
Engine runs on one
cylinder.
Engine runs.
(Both Cylinders)
Won’t Run
(No Spark)
Engine runs.
(Both Cylinders)
Shuts Off OK
Only one cylinder shuts Off
Engine won’t shut Off
1 Closed Diode
1 Open Diode
2 Closed Diodes
2 Open Diodes