Generac Power Systems OHVI GSH 220 User manual

GENERAC®POWER SYSTEMS, INC.
P. O. BOx 310
EaglE, WI 53119
Part No. 0C1103A Printed in USA
Revision A (06/20/06)
0c1103A_Cover.indd 1 6/22/2006 10:31:02 AM

FOREWORD
This manual has been written and published by GENERAC® POWER
SYSTEMS, INC. to aid our dealers’ mechanics, company service person-
nel and general consumers when servicing the products described
herein.
It is assumed that these personnel are familiar with the servicing
procedures for these products, or like or similar products, manufac-
tured and marketed by GENERAC® POWER SYSTEMS, INC. It is also
assumed that they have been trained in the recommended servicing
procedures for these products, which includes the use of mechanics
hand tools and any special tools that might be required.
Proper service and repair is important to the safe, economical and
reliable operation of the products described herein. The trouble-
shooting, testing, service and repair procedures recommended by
GENERAC® POWER SYSTEMS, INC. and described in this manual are
effective methods of performing such operations. Some of these
operations or procedures may require the use of specialized equip-
ment. Such equipment should be used when and as recommended.
We could not possibly know of and advise the service trade of all
conceivable procedures or methods by which a service might be per-
formed, nor of any possible hazards and/or results of each procedure
or method. We have not undertaken any such wide evaluation. There-
fore, anyone who uses a procedure or method not recommended by
the manufacturer must first satisfy himself that neither his safety, nor
the product’s safety, will be endangered by the service or operating
procedure selected.
All information, illustrations and specifications contained in this
manual are based on the latest product information available at the
time of publication. However, GENERAC® POWER SYSTEMS, INC.
reserves the right to change, alter or otherwise improve the product
at any time without prior notice.
Some components or assemblies of the product described in this
manual may not be considered repairable. Disassembly, repair
and reassembly of such components may not be included in this
manual.
The engines described herein may be used to power a wide vari-
ety of products. Service and repair instructions relating to any such
products are not covered in this manual. For information pertaining
to use of these engines with other products, refer to any owner’s or
service manuals pertaining to said products.
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RULES FOR SAFE OPERATION
4-CYCLE ENGINE THEORY
SECTION 1: GENERAL INFORMATION
SECTION 2: IGNITION
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
SECTION 4: MECHANICAL GOVERNOR
SECTION 5: OPTIONAL IDLE CONTROL
SECTION 6: CYLINDER HEAD AND VALVES
SECTION 7: REWIND STARTERS
SECTION 8: ELECTRIC STARTERS AND BATTERIES
SECTION 9: LUBRICATION SYSTEM
SECTION 10: HOUSING AND SHROUDS
SECTION 11: CRANKSHAFT, CAMSHAFT AND BALANCER
SECTION 12: PISTON, RINGS AND ROD
SECTION 13: TROUBLESHOOTING
SECTION 14: SPECIFICATIONS - SMALL FRAME ENGINES
SECTION 15: SPECIFICATIONS - LARGE FRAME ENGINES
1
TABLE OF CONTENTS
A WORD ABOUT SPECIAL TOOLS
Many of the procedures depicted in this manual require the use of special tools. Some of
the tools required are available as Generac parts and are listed as such in this manual.
ATTENTION!
Generac Power Systems does not approve or authorize the use of these engines on All Terrain Vehicles
(ATV’s), go-carts, motorbikes, aircraft products, personal watercraft, or vehicles intended for use in
competitive events. The use of this product in any other than it’s intended application will void the
warranty! Use of these engines in such applications could result in property damage, serious injury
(including paralysis), or even death.
2
3
4
5
6
7
8
9
10
11
12
13
14
1
15
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If you do not understand any portion of this manual, con-
tact Generac or your nearest Generac Authorized Service
Dealer for starting, operating and servicing procedures.
Throughout this publication and on tags and decals affixed
to the engine, DANGER, WARNING and CAUTION blocks
are used to alert you to special instruction about a particular
operation that may be hazardous if performed incorrectly or
carelessly. Observe them carefully.
These safety warnings cannot eliminate the hazards that
they indicate. Strict compliance with the special instructions
while performing the service plus “common sense” are major
measures to prevent accidents.
The following definitions apply to DANGER, WARNING,
CAUTION and NOTE blocks found throughout the manual.
These safety symbols indicate the following:
*
DANGER: After this heading you can read handling,
installing, operating or servicing instructions that,
if not strictly complied with, will result in personal
injury.
*
WARNING: After this heading you can read han-
dling, installing, operating or servicing instructions
that, if not strictly complied with, may result in
personal injury.
*
CAUTION: After this heading you can read instruc-
tions for handling, installing, operating or servicing
the engine that, if not strictly complied with, may
result in damage to equipment and/or property.
NOTE: After this heading you can read explanatory
statements that require special emphasis.
These symbols indicate the following:
*
Points out important safety information that, if not
followed, could endanger personal safety and/or
property of yourself and others.
$
Potential explosion hazard.
#
Potential fire hazard.
+
Potential fire hazard.
RULES FOR SAFE OPERATION
Study these RULES FOR SAFE OPERATION carefully before
operating or servicing this equipment. Become familiar with
the OWNER’S MANUAL and with the engine. The engine
can operate safely, efficiently and reliably only if it is properly
operated and maintained. Many accidents are caused by fail-
ing to follow simple and fundamental rules or precautions.
Generac cannot possibly anticipate every possible circum-
stance that might involve a hazard. The warnings in this
manual and on tags and decals affixed to the equipment,
are therefore, not all-inclusive. If you use a procedure, work
method or operating technique Generac does not specifically
recommend, you must satisfy yourself that it is safe for you
and others. You must also make sure the procedure, work
method or operating technique that you choose does not
render the engine to be unsafe.
*
DANGER: Do not tamper with the engine governed
speed. High operating speeds are dangerous and
increase the risk of personal injury or damage to the
equipment. Operating at low speeds with heavy
load may shorten the engine’s life.
BEFORE OPERATING
• Gasoline is highly FLAMMABLE and its vapors are EXPLO-
SIVE. Do not permit smoking, open flames, sparks or heat
in the area while handling gasoline. Avoid spilling gasoline
on a hot engine. Comply with all of the laws regulating
storage and handling of gasoline.
• Store gasoline and other fuels only in containers designed
and approved for the storage of such materials.
• Add gasoline in a clean, well-ventilated area. Wipe up any
spilled gasoline immediately. If gasoline has been spilled,
let it dry completely before starting the engine.
• Do not overfill the fuel tank. Always allow room for fuel
expansion. If the tank is overfilled, the fuel can overflow
onto a hot engine and cause a FIRE or an EXPLOSION.
• Allow at least two (2) feet of clearance on all sides of the
engine, even while operating it outdoors, or you could
damage the engine.
• Thoroughly inspect the engine for loose or damaged parts
before each use. Do not use the engine until adjustments
or repairs are made.
• Check the oil level in the engine before each use.
• Inspect the engine periodically. Repair or replace all dam-
aged or defective parts immediately.
2
RULES FOR SAFE OPERATION
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3
RULES FOR SAFE OPERATION
• Inspect fuel system frequently for leaks or damage. Repair
or replace any damaged or leaking component immediately.
Never attempt to change, alter or modify the engine fuel
system in any way that might affect safety or compliance
with applicable codes and standards.
WHILE OPERATING
• This engine was designed and manufactured for specific
applications. Do not attempt to modify the equipment or
use it for any application for which it was not designed.
• Generac Power Systems does not approve or authorize the
use of these engines on All Terrain Vehicles (ATV’s), go-
carts, motorbikes, aircraft products, personal watercraft, or
vehicles intended for use in competitive events. The use of
this product in any other than it’s intended application will
void the warranty! Use of these engines in such applications
could result in property damage, serious injury (including
paralysis), or even death.
• Engine exhaust gases contain DEADLY carbon monoxide gas.
This dangerous gas, if breathed in sufficient concentrations,
can cause unconsciousness or even death. Operate this
equipment only in the open air where adequate ventilation
is available.
• Do not insert any object through the cooling slots of the
engine. You could damage the equipment or injure your-
self.
• Do not operate the engine faster than the speed necessary
to operate the equipment. Do not run the engine at high
speed when not operating the equipment.
• This engine requires an adequate flow of cooling air for its
continued proper operation. Never operate the equipment
inside any room or enclosure where the free flow of cooling
air into and out of the equipment might be obstructed. With-
out sufficient cooling air flow, the engine quickly overheats,
damaging the engine or nearby property.
• Do not smoke around the engine. Wipe up any fuel or
oil spills immediately. Never leave oily or fuel soaked rags
around the engine. Keep the area around the engine clean
and free of debris.
• Keep hands, feet, clothing, etc., away from moving parts of
this engine.
• Never operate the engine (a) in the rain; (b) in any enclosed
compartment; (c) if the engine speed changes; (d) if the
engine sparks; (e) if flame or smoke is observed while the
engine is running.
• Never work on this engine or handle any electrical device
while standing in water, while barefoot, or while hands or
feet are wet. DANGEROUS ELECTRIC SHOCK will result.
SERVICE INFORMATION
Service on this engine within and after the warranty
period can be performed by any authorized service
dealer. Service technicians are factory trained and
capable of handling all service needs.
When contacting an authorized service dealer about
parts and service, always supply the complete
model number and serial number of your unit as
given on its data plate decal. See the illustration
below for the location of the decal.
The warranty for this engine is included in the own-
er’s manual.
The engine exhaust from this product contains
chemicals known to the State of California to
cause cancer, birth defects, or other repro-
ductive harm.
WARNING:
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4
4-CYCLE ENGINE THEORY
(A) INTAKE
The piston is travelling from top dead center (TDC) to bottom
dead center (BDC). The cam has opened the intake valve. The
piston's downward movement in the cylinder creates a partial
vacuum in the cylinder. Air at atmospheric pressure is drawn
into the cylinder through the carburetor and is mixed with fuel
in the carburetor. The fuel-air mixture flows through the open
intake valve into the cylinder. When the piston reaches BDC,
the intake stroke is over.
(B) COMPRESSION
As the piston reaches bottom dead center (BDC), both the
intake and exhaust valves are closed. The piston moves upward
toward TDC and the fuel-air mixture is compressed. Just before
the piston reaches TDC, ignition occurs.
(C) IGNITION AND POWER
By the time the piston reaches TDC , combustion is already in
progress. The intake and exhaust valves remain closed as the
expanding gases of combustion force the piston downward.
(D) EXHAUST
The exhaust stroke begins when the piston has reached
BDC and has started its upward movement. The intake valve
is closed. The exhaust valve is open to let gases escape.
If the engine is to run properly, four (4) events must occur in the proper sequence and at the correct time. These events are
(A) intake, (B) compression, (C) ignition and power, and (D) exhaust.
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1-1
SECTION 1: GENERAL INFORMATION
MAINTENANCE SCHEDULE
Every
8 Hours or
Daily
Every
25 Hours
Season
Every
50 Hours
Season
Every
100 Hours
Season
Check Oil Level •
Change Oil Note 1 Note 1
Change Oil Filter Note 1
Service Air Filter
Foam
Pre-Filter
if equipped
Filter
(Note 2)
Replace or Clean
Spark Plug
•
Clean Spark
Arrestor Screen
•
Valve Clearance Note 3 Note 3
NOTE 1: Change oil after the first eight hours of operation on a new
engine. Thereafter, change oil every 50 hours of operation, or after every
100 hours if the engine is equipped with an oil filter, or every season.
Change oil sooner when operating under heavy loads or in dirty or dusty
environments, or under higher ambient temperatures.
NOTE 2: Clean more often when operating in dirty or dusty conditions.
NOTE 3: Check valve lash and adjust if necessary after first 50 hours of
operation and every 100 hours thereafter.
FUEL AND OIL RECOMMENDATIONS
GASOLINE:
We recommend the use of clean, fresh lead-free gasoline.
A minimum of 85 octane is recommended. The use of lead-
free gasoline results in fewer combustion deposits and longer
valve life.
NOTE: Using a fuel additive such as STA-BIL® fuel stabi-
lizer, or an equivalent, will prevent gum deposits from
forming in the engine’s fuel system.
NOTE: Some fuels, called oxygenated or reformulated
gasolines, are gasolines blended with alcohols or ethers.
Excessive amounts of these blends can damage the fuel
system or cause performance problems. Do not use
gasoline which contains Methanol. If any undesirable
operating symptoms occur, use gasoline with a lower
percentage of alcohol or ether.
It is also recommended that gasoline be purchased in small
quantities, not more than a 30 day supply. FRESH gasoline
minimizes gum deposits, and also will ensure fuel volatility
tailored for the season in which the engine will be operated.
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.
RECOMMENDED OIL TYPE:
Using the proper type and weight of oil in the crankcase
is extremely important. Check the oil before each use and
change the oil regularly (see Figures 1-1, 1-2 & 1-3). Failure
to use the correct oil, or using dirty oil, can cause premature
engine wear and failure.
Use only high quality detergent oil rated with API service
classification SF, SG or SH. The recommended oil weights
include the following:
• During summer months: SAE 30. An acceptable substi-
tute is SAE 10W-30. After first oil change, synthetic oil is
acceptable.
• During winter months: SAE 5W-30 or Synthetic 5W-30. DO
NOT USE SAE 10W-40.
CHANGE OIL:
See “Section 14: SPECIFICATIONS” for crankcase oil capaci-
ties. Use no special additives. Make sure that the unit is level
when filling with oil. DO NOT OVERFILL.
IMPORTANT: DO NOT OVERFILL. Check and maintain oil
level regularly. Change oil and filter after first eight (8)
hours of operation.
Thereafter, change oil and filter every 100 hours of opera-
tion. 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.
Remove oil drain plug and drain oil while engine is still warm,
Figure 1-2. Change oil filter (Figure 1-3) and replace drain plug.
1
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1-2
SECTION 1: GENERAL INFORMATION
Figure 1-1. Oil Fill
Remove oil fill cap and refill slowly with new oil of proper
service classification and viscosity grade. Refill to bottom of
threads in oil fill opening.
If engine has optional dipstick, remove dipstick and refill
slowly with new oil of proper service classification and viscosity
grade. Refill to full mark on dipstick. When checking oil level,
dipstick must be turned all the way in for accurate readings.
Start and run engine to check for oil leaks.
CHANGE OIL FILTER:
Replace oil filter every 100 hours. Before installing new filter,
lightly oil filter gasket with fresh clean engine oil. Screw filter
on by hand until gasket contacts filter adapter. Tighten 3/4 to
one full turn farther, Figure 1-3.
Start and run engine at idle for 30 seconds and stop engine.
Recheck oil level and add if required. Restart engine and check
for oil leaks.
Figure 1-2. Oil Drain
Figure 1-3. Oil Filter
REPLACE SPARK PLUGS:
Replace spark plugs every 100 hours of operation or every
season, whichever occurs first. Replace spark plugs if electrodes
are burned away, or the porcelain is cracked. Set spark plug
gap at .76 mm (.030") for all models. Torque spark plugs to
20.0 Nm (180 in. lbs.).
Figure 1-4. Setting Spark Plug Gap
Note: For proper spark plug replacement, refer to the
owner’s manual for the specific product.
AIR CLEANER MAINTENANCE:
*
WARNING: NEVER OPERATE ENGINE WITH AIR
CLEANER ASSEMBLY OR AIR CLEANER CARTRIDGE
REMOVED. FIRE MAY RESULT.
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 bore to wear quickly. As the rings and
cylinder bore become worn, these abrasive particles enter the
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1-3
SECTION 1: GENERAL INFORMATION
crankcase and contaminate the oil, forming an abrasive mixture
which will cause wear on all of the internal moving parts.
The air cleaner on every engine brought in for a check up
or repair should be examined and serviced. If the air cleaner
shows signs of neglect, show it to the customer before clean-
ing. Instruct the customer on proper care, to assure long
engine life.
Note: Replace air cleaner gaskets and mounting gaskets
that are worn or damaged, to prevent dirt and dust from
entering engine due to improper sealing. Replace bent
air cleaner mounting bracket if necessary.
SERVICE DUAL ELEMENT AIR CLEANERS:
Remove and service foam pre-cleaner every 25 hours or every
season, whichever occurs first. Service cartridge every 50 hours
or every season, whichever occurs first.
Note: The air cleaner assemblies on some equipment
may have been supplied by the equipment manufacturer.
See the equipment manufacturer’s owner’s manual for
service information specific to that product.
TROUBLESHOOTING
Most complaints concerning engine operation can be clas-
sified 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.
SYSTEMATIC CHECK:
If the engine will not start and the cause of malfunction is
not readily apparent, perform a systematic check in the fol-
lowing order:
1. Fuel
2. Ignition
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. The basic check-up
procedure is the same for all engine models, while any varia-
tion, by model, will be shown under the subject heading.
CHECK FUEL:
• Are the tanks full?
• Is the fuel stale?
• Is the tank vent open?
• Is the fuel shutoff valve open?
CHECK IGNITION:
See Section 2 “IGNITION”.
CHECK COMPRESSION:
To check engine compression, remove the spark plug. Insert
an automotive type compression gauge into the spark plug
hole. Crank the engine until there is no further increase in
pressure. The highest reading obtained is the engine compres-
sion pressure.
190-220cc Engines: Minimum 60psi
320-410cc Engines: Minimum 55psi
These minimum readings may appear low. This is due to the
engine being equipped with a compression release mechanism
to minimize starting effort. Actual running compression will
be much higher (see Page 11-3).
If compression is poor, look for one or more of the follow-
ing causes:
• Loose cylinder head bolts.
• Failed cylinder head gasket.
• Burned / worn valves or valve seats.
• Insufficient valve clearance.
• Warped cylinder head.
• Warped valve stem or worn valve guides.
• Worn or broken piston ring(s).
• Worn or damaged cylinder bore.
• Broken connecting rod.
CYLINDER LEAKDOWN TEST
A cylinder leakdown tester may be used to test the sealing
capability of the compression components of each cylinder
and quickly identify the problem component.
A cylinder leak down test will indicate the condition of the
cylinder. It will assist in troubleshooting the engine’s condition
such as leaking valves or rings.
On the tester there will be two gauges, one will be the
incoming air pressure and the other will measure the percent
of cylinder leakage.
1
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1-4
SECTION 1: GENERAL INFORMATION
CYLINDER LEAK DOWN TEST PROCEDURE:
1. Piston must be at TDC.
2. Install the tester into the spark plug hole
3. Pressurize the cylinder to 90 psi.
4. Observe the leakage of the cylinder and where the air is
coming from.
NOTE: If leaking into intake or exhaust port, check lash,
valve face, and seat condition.
INLET GUAGE
PRESSURE SET
POINT
RED RANGE INDICATES
UNACCEPTABLE LEAKAGE
GREEN RANGE INDICATES
ACCEPTABLE LEAKAGE
NEEDLE INDICATES
MINIMAL AIR LEAKAGE
AIR PRESSURE
REGULATOR
REGULATOR
ADJUSTMENT
KNOB
COMPRESSED
AIR IN OUTLET GUAGE
PRESSURE
OUTLET
GUAGE
0
0
0
GENERAC
Figure 1-12. Cylinder Leakdown Tester
RESULTS:
1. 0-10% Cylinder is good
2. 10-30% there may be a problem
3. 30-100% Cylinder requires repair
THINGS WHICH AFFECT BOTH CYLINDERS:
1. Carburetion
2. Crankcase vacuum
3. Ignition timing
a. A partially sheared flywheel key will effect ignition timing
and engine performance.
THINGS WHICH AFFECT ONE CYLINDER:
1. Spark plug
a. A fouled spark plug may indicate that carburetor is out
of adjustment.
2. Leak in spark plug wire
3. Head gasket
4. Intake manifold
a. A leak at either end of the intake manifold will only affect
one cylinder, not both.
5. Valves
6. Rings
7. Piston
8. Cylinder
EQUIPMENT AFFECTING ENGINE OPERATION
Frequently, what appears to be a problem with engine opera-
tion, such as hard starting, vibration, etc., may be the fault of
the equipment powered rather than the engine itself. Listed
are the most common effects of equipment problems, and
what to look for as the most common cause.
HARD STARTING OR WILL NOT START:
1. Loose belt - a loose belt like a loose blade can cause a
backlash effect, which will counteract engine cranking
effort.
2. Starting under load - see if the unit is disengaged when
engine is started; or if engaged, should not have a heavy
starting load.
3. Check remote control assembly for proper adjustment.
4. Check interlock system for shorted wires, loose or corroded
connections, or defective modules or switches.
ENGINE WON'T STOP:
1. Check equipment ignition stop switch.
2. Check for loose or disconnected equipment stop switch
wire.
3. Check ground wire harness on engine.
a. See Section 2 for test procedure.
VIBRATION:
1. Unit load out of balance - remove and balance.
2. Mounting bolts loose - tighten.
POWER LOSS:
1. Bind or drag in unit- if possible, disengage engine and
operate unit manually to feel for any binding action.
2. Unit load has excess drag.
NOISE:
1. Engine coupling or pulley - an oversize or worn coupling
can result in knocking, usually under acceleration. Check
for fit or tightness.
2. Equipment needs lubrication.
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2-1
SECTION 2: IGNITION
GENERAL
The ignition system typically used on single cylinder engines
is a solid-state (breakerless) type. The system utilizes a magnet
on the engine flywheel to induce a relatively low voltage into
an ignition coil assembly. Ignition coil internal components
increase the voltage and deliver the resulting high voltage
across the spark plug gap.
The ignition coil houses a solid-state circuit board that con-
trols ignition timing. Timing is fixed, nonadjustable and spark
advance is automatic.
MAJOR COMPONENTS
Major components of the ignition system include (a) the igni-
tion coil assembly, (b) the spark plug, (c) the engine run switch
and (d) the engine flywheel (see Figures 2-1 and 2-4).
SPARK
PLUG
ENGINE
RUN SWITCH
IGNITION
COIL
ASSEMBLY
Figure 2-1. Ignition System Components
IGNITION COIL ASSEMBLY
Solid-state components encapsulated in the ignition coil are
not accessible and cannot be serviced. If the coil is defective,
the entire assembly must be replaced. The air gap between the
coil and the flywheel magnet is fixed and nonadjustable.
The ignition coil assembly (Figure 2.2) consists of (a) ignition
coil, (b) spark plug high tension lead and (c) spark plug boot.
Figure 2-2. Ignition Coil Assembly
SPARK PLUG
The spark plug should be cleaned and regapped periodically.
The plug should be replaced every 100 hours of operation or
once annually, whichever comes first.
Set spark plug gap to 0.030 inch (0.76mm) (Figure 2-3).
Note: For proper spark plug replacement, refer to the
owner’s manual for the specific product. Always use
original GENERAC® replacement parts.
SET PLUG GAP AT 0.030 inch
(0.76 mm)
Figure 2-3. Setting Spark Plug Gap
FLYWHEEL
CHECKING FLYWHEEL MAGNET:
The flywheel magnet rarely loses its magnetism. If you
suspect a magnet might be defective, a rough test can be
performed as follows:
1. Place the flywheel on a wooden surface.
2. Hold a screwdriver at the extreme end of its handle and
with its point down.
3. Move the tip of the screwdriver to about 3/4 inch (19mm)
from the magnet. The screwdriver blade should be pulled
in against the magnet.
FLYWHEEL KEY:
The flywheel’s taper is locked on the crankshaft taper by the
torque of the flywheel nut. A keyway is provided for alignment
only and theoretically carries no load.
If the flywheel key becomes sheared or even partially sheared,
ignition timing can change. Incorrect timing can result in hard
starting or failure to start.
FLYWHEEL REMOVAL:
Use a strap wrench to prevent the flywheel from turning.
Remove the FLYWHEEL NUT. Then, remove the CONICAL
WASHER and the STARTER CUP.
Use a commercially available flywheel puller to remove the
flywheel from the engine tapered shaft.
2
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2-2
SECTION 2: IGNITION
FLYWHEEL INSTALLATION:
Align the keyway in the flywheel with the woodruff key on
the crankshaft. Install the flywheel, the starter cup and the
conical washer. Install the flywheel nut and tighten to the
proper torque.
NOTE: The conical washer must be installed in the proper
direction (see Figure 2-4) with the convex side facing out
(away from the flywheel).
WOODRUFF KEY
FLYWHEEL
FLYWHEEL
STARTER CUP
STARTER
CUP
CONICAL
WASHER
FLYWHEEL
NUT
FLYWHEEL
NUT
CONVEX SIDE OF CONICAL
WASHER FACING OUT
Figure 2-4. Exploded View of Flywheel Assembly
TESTING THE IGNITION SYSTEM
The condition of the ignition system can be accurately
diagnosed using an ignition tester, (Generac P/N 0C5969) as
follows:
1. Disconnect the high tension lead from the spark plug.
2. See Figure 2-5. Attach the spark tester clamp to the engine
cylinder head (frame ground). Attach the spark plug high
tension lead to the tester terminal.
3. Crank the engine rapidly. If spark jumps the gap of the
spark tester, you may assume the ignition system is operat-
ing satisfactorily.
Figure 2-5. Testing Ignition System
NOTE: If the flywheel key is sheared or partially sheared,
spark can jump the tester gap. However, loss of correct
ignition timing may result in hard starting or no start-
ing at all.
4. To determine if an engine miss is ignition related, connect
the spark tester in series with the high tension lead and the
spark plug (Figure 2-6). Then, test the system as follows:
a. Start the engine.
b. If spark jumps the tester gap regularly but the miss contin-
ues, the problem is in the spark plug or in the fuel system.
A spark miss will be readily apparent.
Figure 2-6. Checking for Engine Miss
NOTE: The ignition system described in this section is
typically used on horizontal shaft engines. The ignition
system used on all vertical shaft (RV) engines differs from
that of horizontal shaft engines. See "SERVICE MANUAL
COMPUTER CONTROLLED VARIABLE SPEED RV GENERA-
TORS," Manual Part No. 094468-A.
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3-1
AIR CLEANER
SERVICING:
The engine will not run properly and may be damaged if it
is run with a dirty air cleaner.
Clean or replace the paper filter every 25 hours of operation
or once annually, whichever occurs first. Clean or replace the
paper filter more often if operating in extremely dusty or dirty
conditions.
Clean or replace the foam pre-cleaner every 25 hours of
operation; more frequently under dirty or dusty conditions.
FOAM PRE-CLEANER:
To clean or replace the foam pre-cleaner:
1. Remove the air cleaner cover, then remove the foam pre-
cleaner.
2. Wash the foam pre-cleaner in soapy water.
3. Squeeze the pre-cleaner dry with a clean cloth. DO NOT
TWIST.
NOTE: If the pre-cleaner is still dirty after washing and
drying it, replace it with a new filter
4. Apply enough clean engine oil to saturate the pre-
cleaner.
5. Wrap the pre-cleaner in a clean dry cloth and squeeze out
excess oil. DO NOT TWIST. Set the pre-cleaner aside.
Figure 3-1. Typical Air Cleaner
PAPER FILTER:
1. Remove the air cleaner cover.
2. Remove the foam pre-cleaner and service it, if necessary.
3. Remove the paper filter.
4. Clean the paper filter by tapping gently on a flat surface.
If it is very dirty, replace it.
5. Clean the air cleaner cover. Then, install the foam pre-
cleaner into the cover.
6. Insert the paper filter into the cover so it holds the pre-
cleaner in place.
7. Assemble the pre-cleaner, paper filter and cover to the air
cleaner base.
AIR CLEANER BOX REMOVAL (LARGE FRAME):
If the air cleaner box must be removed for further engine
disassembly, do the following (see Figure 3-2):
1. Remove the air cleaner cover.
2. Remove the foam pre-cleaner and paper filter.
3. Remove the choke knob.
4. Remove the breather hose.
5. Remove the two nuts and corresponding washers from
the carburetor mounting bolts.
6. Remove the two capscrews and corresponding washers
from the lower part of the air cleaner box.
NOTE: The carburetor will be loose after removal of the
air cleaner box. Do not allow the carburetor to drop.
Note: Be careful not to stretch or bind the wires con-
nected to the Low Oil Indicator and Start/Stop switch.
BREATHER HOSE
AIR CLEANER BOX
GASKET
CHOKE KNOB
PAPER FILTER
FOAM
PRE-CLEANER
NUT, WASHER
AND LOCK WASHER
NUT AND WASHER
CAPSCREW
AND WASHERS
Figure 3-2. Exploded View of Air Cleaner Box
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
3
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3-2
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
AIR CLEANER BOX REMOVAL (SMALL FRAME):
If the air cleaner box must be removed for further engine
disassembly, follow Steps 1-4 from Large Frame Air Cleaner
Box Removal. Then do the following:
1. Remove the cap screw in the upper part of the air cleaner
box and the two phillips head screws in the lower part of
the air cleaner box (see Figure 3-3).
*
CAUTION! Removal of the two phillips head screws
on a choke style carburetor/air cleaner box combina-
tion also will loosen the carburetor from its mount.
Be careful not to let the carburetor drop, as damage
to the carburetor and/or governor rod and anti-lash
spring may result.
FOAM
PRE-CLEANER
PAPER FILTER
AIR CLEANER BOX
BREATHER HOSE
CAP SCREW
PHILLIPS HEAD SCREWS
GASKET
Figure 3-3. Removal of Air Cleaner Box,
Primer Style Carburetor
AIR CLEANER BOX INSTALLATION:
Install the air cleaner box to the engine and carburetor as
follows:
1. Using a new gasket, place the air cleaner box on the
carburetor, line up the holes and install the two nuts and
corresponding washers to the carburetor mounting bolts
(see Figure 3-2). Refer to “TORQUE SPECIFICATIONS” in
the back of this manual for proper torque.
Note: On large frame engines the nut on the right side
(toward the rear of the engine) uses only a flat washer.
The nut on the left side (toward the front of the engine)
uses a lock washer and a flat washer (see Figure 3-2).
2. Install the capscrews in the air cleaner box (see Figure 3-2).
Refer to “TORQUE SPECIFICATIONS” in the back of this
manual for proper torque.
3. Reinstall the breather hose.
4. Reinstall the choke knob.
5. Install the filters and cover as stated in the preceding sections
on filter maintenance.
CARBURETION
GENERAL:
Proper engine performance depends on the carburetion
system. The use of clean, fresh fuel and a well maintained air
cleaner is extremely important to engine operation, as well as
engine reliability and power.
COMMON CARBURETOR PROBLEMS:
Most causes of carburetor problems are related to the use
of stale, gummy fuel and the ingestion of dirt. Prior to servic-
ing any carburetor, be sure to check for evidence of these
conditions.
Gasoline that is left in the system for long periods can form
gum or varnish deposits that will adversely affect carburetor
operation.
NOTE: Use of a good fuel stabilizer will minimize the
formation of gum deposits during storage. Add the
stabilizer to the gasoline in the fuel tank or in the stor-
age container. Follow the mix ratio recommended on
the stabilizer container. After adding the stabilizer to
the engine fuel tank, run the engine for about ten (10)
minutes so it will enter the carburetor. A brand name
stabilizer can be purchased at a Generac Air-Cooled
Industrial Engine Dealer.
SERVICE TIP:
Carefully inspect the carburetor choke and throttle shafts for
wear. Grasp each shaft and attempt to move it horizontally
and vertically. Maximum allowable end play for choke and
throttle shafts is 0.004 inch (0.1mm). Replace if excessive play
is evident.
CARBURETOR REMOVAL:
1. Remove the air cleaner box as outlined in “AIR CLEAN-
ER BOX REMOVAL.”
2. Disconnect the governor rod and anti-lash spring from the
throttle arm of the carburetor.
3. Slide the carburetor off of its mounting bolts.
CARBURETOR DISASSEMBLY:
To disassemble the carburetor, proceed as follows (See Figure
3-5 or 3-6):
1. Remove the FLOAT BOWL NUT and the FIBER WASHER.
Then remove the FLOAT BOWL.
2. Remove the FLOAT PIN. Then remove the FLOAT, and FUEL
INLET VALVE.
3. Remove the IDLE SPEED STOP SCREW along with its
SPRING.
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3-3
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
4. Rotate the THROTTLE PLATE to it's closed position and
remove two THROTTLE PLATE SCREWS.
5. Rotate the CHOKE PLATE (if equipped) to its closed position
and remove the CHOKE RETAINER SPRING.
6. Remove the CHOKE SHAFT (if equipped) and the CHOKE
SHAFT SEAL.
7. Remove the THROTTLE SHAFT and the THROTTLE SHAFT
SEAL.
CARBURETOR GASKET CARBURETOR
CARBURETOR
MOUNTING
BOLT
GOVERNOR ROD AND
ANTI-LASH SPRING
Figure 3-4. Removal of Carburetor
CARBURETOR CLEANING AND INSPECTION:
1. Separate out all nonmetallic parts. Then, clean metallic
parts with solvent or commercial carburetor cleaner. DO
NOT PERMIT NONMETALLIC PARTS TO CONTACT SOLVENT
OR CLEANER.
2. Inspect the THROTTLE SHAFT. Replace if worn or dam-
aged.
3. Inspect the CHOKE SHAFT (if equipped). Replace if worn
or damaged.
4. Inspect the FLOAT BOWL. It must be free of dirt and
corrosion.
5. Inspect the FLOAT Replace if damaged.
6. After all metallic parts have been cleaned, blow out car-
buretor passages with compressed air.
*
When working with compressed air and solvents or
cleaners, be sure to wear appropriate eye protection
to avoid personal injury.
*
Generac recognizes that there are spray type carbure-
tor cleaners on the market, however Generac does not
authorize the use of carburetor cleaners. Also, Generac
does not recommend soaking a carburetor in any
cleaners since the carburetor might be damaged.
NOTE: On small frame engines a MAIN JET TUBE is pressed
into the carburetor body to a measured depth. Do NOT
attempt to remove this tube. Tube movement will
adversely affect carburetor metering characteristics.
CARBURETOR REASSEMBLY:
Reassemble the carburetor in the reverse order of disassem-
bly. The following rules apply:
1. Blow metallic parts dry with compressed air.
2. A notch on the FUEL INLET VALVE mates with the FLOAT
(See Figures 3-5 and 3-6).
3. The FLOAT SETTING is FIXED and NONADJUSTABLE.
4. Before tightening the FLOAT BOWL NUT (Item 4), make
sure the FLOAT BOWL is properly aligned with the GASKET
and the CARBURETOR BODY.
CARBURETOR INSTALLATION:
Using a new gasket, reinstall the carburetor as follows:
1. Slide the new carburetor gasket over the carburetor
mounting bolts followed by the carburetor.
2. Connect the governor rod and anti-lash spring.
3. Install the air cleaner box, filters and air cleaner cover as
described in “AIR CLEANER BOX INSTALLATION.”
CARBURETOR ADJUSTMENT
INITIAL ADJUSTMENTS:
(See Figure 3-7)
1. The IDLE SPEED STOP SCREW is located at top of the
carburetor and contacts the THROTTLE SHAFT. After reas-
sembling the carburetor, complete an initial adjustment of
the STOP SCREW as follows:
a. Close the THROTTLE PLATE.
b. Hold the throttle plate in its closed position and back out
the idle speed stop screw.
c. Turn the idle speed stop screw until it just contacts the
stop tang of the throttle shaft. Then turn the idle speed
stop screw in one turn further.
NOTE: Final adjustment of idle speed can be accom-
plished with the engine running. Engines equipped with
optional automatic idle control require a special proce-
dure for idle speed adjustment. See Section 4, "Optional
Idle Control."
NOTE: The carburetor is equipped with a fixed main jet,
which requires no adjustment.
3
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3-4
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1 1 Carburetor Body
2 1 Float
3 1 Float Bowl
4 1 Bowl Nut (Main Jet)
5 1 Fiber Washer
6 1 Bowl Gasket
7 1 Float Pin
8 1 Inlet Valve
9 1 Fuel Inlet
10 1 Cap Screw
11 1 Throttle Shaft Felt Washer
12 1 Throttle Shaft Spring
13 1 Screw
14 1 Throttle Valve
15 1 Throttle Shaft
16 1 Idle Jet
17 1 Spring
18 1 Idle Speed Screw
19 1 Primer Bulb
20 1 Primer Bulb Retainer
ITEM QTY DESCRIPTION ITEM QTY DESCRIPTION
Figure 3-5. Exploded View of Typical Carburetor (Small Frame Engine)
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3-5
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
1
2
3
4
5
6
7
8
9
10
11 12
13
14
15
16
17 18
1 1 Carburetor Body
2 1 Float
3 1 Float Bowl
4 1 Bowl Nut
5 1 Fiber Washer
6 1 Bowl Gasket
7 1 Fuel Inlet Valve
8 1 Float Pin
9 1 Main Jet
10 1 Choke Shaft Seal
11 1 Choke Shaft
12 1 Choke Plate
13 2 Choke Plate Screw
14 1 Throttle Shaft
15 1 Throttle Shaft Seal
16 2 Throttle Plate Screw
17 1 Idle Speed Stop Screw
18 1 Spring
ITEM QTY DESCRIPTION ITEM QTY DESCRIPTION
Figure 3-6. Exploded View of Typical Carburetor (Large Frame Engine)
3
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3-6
SECTION 3: AIR INTAKE SYSTEM AND CARBURETION
FINAL ADJUSTMENT:
The following instructions apply to engines NOT equipped
with automatic idle control. If the unit has an automatic idle
control, refer to the Section 5, "Optional Idle Control."
If the engine is used to drive an AC generator set, use an
AC frequency meter to measure engine speed/frequency. Con-
nect the AC frequency meter across one of the generator’s AC
output receptacles or across the generator’s AC power winding
output leads. Read the AC output frequency in HERTZ (cycles
per second).
If the engine is used in some other application (pressure
washer, pump, air compressor, etc.), use a tachometer to read
the engine rpm.
1. Start the engine and allow a sufficient warm-up period.
2. Hold the carburetor throttle lever against the idle speed
stop screw, then turn the idle speed stop screw until the
correct idle speed is obtained.
a. If the driven unit is an AC generator and an AC frequency
meter is used, the correct high no-load speed is between
62-63 Hertz. (3720-3780 rpm).
b. If the unit is not a generator, adjust the high no-load speed
stop screw to obtain about 3750 rpm.
Figure 3-7. Idle Speed Stop Screw
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4-1
SECTION 4: MECHANICAL GOVERNOR
GOVERNOR OPERATION
1. The GOVERNOR SPRING tends to pull the LEVER and GOV-
ERNOR ROD toward the "INCREASE RPM" direction.
2. As engine speed increases, centripetal force acts on the
FLYWEIGHT. When FLYWEIGHT centripetal force exceeds
SPRING force, the governor SPOOL is moved axially by
FLYWEIGHT force. This causes the GOVERNOR ARM to
rotate, which then moves the LEVER and GOVERNOR ROD
toward a "DECREASE RPM" direction.
3. As engine speed decreases, a point is reached where gov-
ernor SPRING force is greater than FLYWEIGHT centripetal
force. SPRING force then moves the LEVER and GOVER-
NOR ROD toward "INCREASE RPM."
4. Governor action consists of a series of small rpm over-
shoots and undershoots, as SPRING force increases rpm
and FLYWEIGHT centripetal force decreases rpm.
5. The point at which SPRING tension and FLYWEIGHT force
are equal is the governed speed of the engine.
SPOOL
FLYWEIGHT
CRANKSHAFT
(PTO END)
CRANKSHAFT
GEAR
GOVERNOR
GEAR
TO THROTTLE LINK
DECREASE RPM
INCREASE RPM
CENTRIPETAL
FORCE
SHAFT
SPRING
SPEED
ADJUST
Figure 4-1. Governor Operating Diagram
GOVERNOR INTERNAL PARTS
See Figure 4-2. A governor gear shaft is pressed into a bore
in the engine crankcase cover. Internal governor components
include (a) a THRUST WASHER, (b) GOVERNOR GEAR ASSEM-
BLY, (c) SNAP RING, (d) GOVERNOR SPOOL, and (e) GOVERNOR
ARM. A lock pin and washer retain the governor arm in the
crankcase cover.
The governor gear assembly houses the governor fly-
weights.
Flyweight movement causes the spool to move axially. In
turn, axial movement of the spool results in rotation of the
governor arm.
GOVERNOR
GEAR SHAFT THRUST
WASHER GOVERNOR
GEAR ASSEMBLY
GOVERNOR SPOOL
GOVERNOR ARM
SNAP RING
WASHER
LOCK PIN
Figure 4-2. Internal Governor Parts
GOVERNOR EXTERNAL PARTS
WITHOUT AUTOMATIC IDLE CONTROL:
External governor parts for units without automatic idle
control are shown in Figure 4-3. Parts include (a) a GOVER-
NOR LEVER, (b) a GOVERNOR ROD, (c) ANTI-LASH SPRING,
(d) a SPEED ADJUST BOLT, (e) a SPEED ADJUST NUT, and (f) a
GOVERNOR SPRING.
The governor lever is clamped to the governor arm, so that
arm rotation is imparted to the lever. The governor rod con-
nects to the governor lever at one end and to the carburetor
throttle arm at it's other end. Governor spring tension is adjust-
able by means of the speed adjust bolt and nut.
Engine speed can be adjusted by changing the tension of
the governor spring. Governor spring tension can be changed
by turning a locknut on the governor adjusting bolt.
SPEED
ADJUST
NUT
SPEED
ADJUST
SCREW
GOVERNOR
SPRING
GOVERNOR
LEVER
GOVERNOR
LEVER CLAMP
BOLT
GOVERNOR
ARM
GOVERNOR
ROD
ANTI-LASH
SPRING
Figure 4-3. External Governor Parts
(Units without Idle Control)
4
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4-2
SECTION 4: MECHANICAL GOVERNOR
WITH AUTOMATIC IDLE CONTROL:
Models equipped with automatic idle control (Section 5)
have the same external governor parts as shown in Figure
4-3 with the addition of an idle control solenoid as shown in
Figure 4-4.
Figure 4-4. External Governor Parts
(Units with Idle Control)
REMOVAL OF GOVERNOR EXTERNAL PARTS:
Before any covers and shrouds can be removed from the
engine, the governor external parts must be removed. Refer
to Figures 4-3 and 4-4 for identification of the parts described
in the following procedure.
1. Remove the CAPSCREW from the IDLE CONTROL BRACKET
if equipped with automatic idle control (Figure 4-4).
2. Loosen the GOVERNOR LEVER CLAMP BOLT (Figure 4-3).
3. Loosen SPEED ADJUST NUT until the GOVERNOR SPRING
can be removed (Figure 4-3).
4. Lift the GOVERNOR LEVER from the GOVERNOR ARM
(Figure 4-3).
5. Disconnect the GOVERNOR ROD and ANTI-LASH SPRING
from the GOVERNOR LEVER (Figure 4-3).
Set the governor external parts aside.
INSTALLATION OF GOVERNOR EXTERNAL PARTS:
After the installation of the engine shrouds and covers,
reinstall the governor external parts as follows (refer to Figure
4-3):
1. Reattach the GOVERNOR ROD and ANTI-LASH SPRING to
the GOVERNOR LEVER.
2. Slide the GOVERNOR LEVER onto the GOVERNOR ARM.
3. Tighten the GOVERNOR LEVER CLAMP BOLT.
4. Reinstall the GOVERNOR SPRING to the GOVERNOR
LEVER and SPEED ADJUST SCREW, then tighten the SPEED
ADJUST NUT accordingly.
5. Reinstall the CAPSCREW into the IDLE CONTROL BRACKET
if equipped with automatic idle control (Figure 4-4). See
BLOWER HOUSING SCREW under “TORQUE SPECIFICA-
TIONS,” in the back of this manual, for proper tightness.
For proper governor adjustment, refer to “GOVERNOR
ADJUSTMENT” on the next page.
GOVERNOR GEAR SHAFT REPLACEMENT
*
CAUTION! DO NOT TWIST THE GEAR SHAFT WITH A
VISE GRIP OR ANY OTHER TOOL. THIS COULD RESULT
IN ENLARGEMENT OF THE SHAFT BOSS.
INSPECTION:
If the governor gear shaft is scored, damaged or worn, it
should be replaced.
REMOVAL:
If it becomes necessary to replace the governor gear shaft,
remove the crankcase cover (See Section 11). Use care to avoid
damage to the shaft boss area of the crankcase cover. Clamp
the shaft in a vise, then tap the flange with a wooden or plastic
mallet to remove the shaft.
INSTALLATION:
Start the new shaft into the shaft boss by tapping lightly with
a soft mallet. Add red Loctite®to the shaft. Then, use a press
or vise to press the shaft into the boss. The shaft is properly
positioned when its end is just flush with the external boss of
the crankcase cover. Be sure to wipe away any excess Loctite®
from the flange.
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