Generac Power Systems GN190H, GN190RV, GN191RV, GN191H, GN220RV Service And Repair Manual
...
FOREWORD
This manual has been written and published by GENERAC
POWER SYSTEMS, INC. to aid our dealers’ mechanics, company service personnel 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, manufactured 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 troubleshooting, 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 equipment. 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 performed, nor of any possible hazards and/or results of each procedure or method. We have not undertaken any such wide evaluation.
Therefore, 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 variety
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.
TABLE OF CONTENTS
DIMENSIONS AND FEATURES ............................ 3-7
4-CYCLE ENGINE THEORY ...................................... 8
SECTION 1: GENERAL ...................................... 9-12
PURPOSE AND SCOPE OF MANUAL ................................ 8
SMALL FRAME ENGINES .................................................. 8
LONG BLOCK .................................................................. 8
ENGINE I.D. NUMBER/SERIAL NUMBER ............................ 8
ENGINE CARE ................................................................ 10
Recommended Fuels .................................................. 10
Recommended Engine Oil .......................................... 10
Change Oil Filter ........................................................ 10
STORAGE INSTRUCTIONS .............................................. 10
TUNE-UP PROCEDURE .............................................. 10-11
OVERSIZE PARTS ............................................................ 12
SECTION 2: AIR CLEANERS AND CARBURETION 14-17
AIR CLEANER ................................................................ 14
Servicing .................................................................... 14
Foam Pre-Cleaner ...................................................... 14
Paper Filter ................................................................ 14
Air Cleaner Box Removal............................................ 14
Air Cleaner Box Installation ........................................ 15
CARBURETION .............................................................. 15
General...................................................................... 15
Common Carburetor Problems .................................. 15
Adjustable and Fixed Main Jet.................................... 15
Carburetor Removal .................................................. 16
Carburetor Disassembly.............................................. 16
Cleaning and Inspection ............................................ 16
Carburetor Installation .............................................. 16
SECTION 3: MECHANICAL GOVERNOR.......... 18-20
GOVERNOR OPERATION ................................................ 18
GOVERNOR INTERNAL PARTS ........................................ 18
GOVERNOR EXTERNAL PARTS .................................. 18-19
Removal of Governor External Parts ...................... 18-19
Installation of Governor External Parts ........................ 19
GOVERNOR GEAR SHAFT REPLACEMENT ...................... 19
Inspection .................................................................. 19
Removal .................................................................... 19
Installation ................................................................ 19
LINKAGE INSTALLATION ................................................ 19
GOVERNOR ADJUSTMENT ........................................ 19-20
Initial Adjustment.................................................. 19-20
Running Adjustment .................................................. 20
SECTION 4: OPTIONAL IDLE CONTROL .......... 22-23
GENERAL ...................................................................... 22
OPERATING INSTRUCTIONS............................................ 22
Before Start-up .......................................................... 22
Engine Running.......................................................... 22
CIRCUIT OPERATION ...................................................... 22
IDLE CONTROL ADJUSTMENT ........................................ 23
General...................................................................... 23
Initial Adjustment ...................................................... 23
Final Adjustment........................................................ 23
SECTION 5: REWIND STARTERS...................... 24-25
GENERAL ...................................................................... 24
REWIND ASSEMBLY REMOVAL ...................................... 24
DISASSEMBLY (OLD STYLE) ............................................ 25
REASSEMBLY.................................................................. 25
DISASSEMBLY (NEW STYLE)............................................ 25
SECTION 6: ELECTRIC STARTERS AND BATTERIES ..26-28
INTRODUCTION ............................................................ 26
STARTER CONTACTOR SYSTEM...................................... 26
HEAVY DUTY SWITCH SYSTEM...................................... 26
STARTER MOTOR OPERATING PRINCIPLES...................... 26
THE BENDIX DRIVE ........................................................ 26
STARTER MOTOR REPAIRS ........................................ 26-27
Starter Motor Removal .............................................. 26
Starter Motor Installation ...................................... 26-27
TESTING THE STARTER MOTOR ...................................... 27
Checking the Pinion .................................................. 27
Tools for Starter Performance Test .............................. 27
Starter Performance Test ............................................ 27
BATTERY MAINTENANCE .............................................. 27
General...................................................................... 27
Inspecting the Battery ................................................ 27
Electrolyte Level ........................................................ 27
TESTING A BATTERY ................................................ 27-28
SECTION 7: COVERS AND SHROUDS .................. 29
GENERAL ...................................................................... 29
Installation of Covers and Shrouds ............................ 29
1
TABLE OF CONTENTS
GENERAC
SECTION 8: IGNITION SYSTEM ...................... 30-31
GENERAL ...................................................................... 30
MAJOR COMPONENTS .................................................. 30
IGNITION COIL ASSEMBLY.............................................. 30
SPARK PLUG .................................................................. 30
FLYWHEEL ................................................................ 30-31
Checking Flywheel Magnet ........................................ 30
Flywheel Key.............................................................. 30
Flywheel Removal ................................................ 30-31
Flywheel Installation .................................................. 31
TESTING THE IGNITION SYSTEM .................................... 31
SECTION 9: VALVE TRAIN .............................. 32-36
MAJOR COMPONENTS .................................................. 32
DISASSEMBLY .......................................................... 32-33
VALVE SERVICE .............................................................. 33
Valve ..........................................................................33
Valve Seats ................................................................ 33
Valve Guides.............................................................. 34
Valve Tappets ............................................................ 34
Valve Springs.............................................................. 34
INSTALLATION .......................................................... 34-35
ADJUSTING VALVE CLEARANCE .................................... 36
INSTALL ROCKER ARM COVER ........................................36
SECTION 10: PISTON, RINGS AND ROD ........ 38-41
GENERAL ...................................................................... 38
REMOVAL ...................................................................... 38
PISTON .................................................................... 38-39
Removal from Connecting Rod .................................. 38
Check Piston for Wear .......................................... 38-39
PISTON RINGS ................................................................ 39
General...................................................................... 39
Description ................................................................ 39
Ring End Gap........................................................ 39-40
CONNECTING ROD ........................................................ 40
ASSEMBLY AND INSTALLATION ................................ 40-41
Assembly .................................................................. 40
Installation ................................................................ 41
CYLINDER SERVICE ........................................................ 41
Inspection .................................................................. 41
Reboring the Cylinder ................................................ 41
SECTION 11: CRANKSHAFT AND CAMSHAFT 42-45
CAMSHAFT REMOVAL .................................................. 42
Removal of Crankcase Cover...................................... 42
Camshaft Removal .................................................... 42
CRANKSHAFT REMOVAL................................................ 42
CAMSHAFT INSPECTION ................................................ 43
CRANKSHAFT INSPECTION........................................ 43-44
Crankshaft Proper...................................................... 43
Crankshaft Sleeve Bearing.......................................... 44
COMPRESSION RELEASE .......................................... 44-45
CRANKSHAFT INSTALLATION ........................................ 45
CAMSHAFT INSTALLATION ............................................ 45
SECTION 12: LUBRICATION ............................ 46-50
GENERAL ...................................................................... 46
OIL FLOW ...................................................................... 46
OIL PICKUP ASSEMBLY .................................................. 46
Description ................................................................ 46
Inspection .................................................................. 46
OIL PUMP ................................................................ 46-47
Description ................................................................ 46
Inspection .................................................................. 47
CRANKSHAFT OIL SEALS ................................................ 47
PRESSURE RELIEF VALVE ................................................ 48
Description ................................................................ 48
Inspection .................................................................. 48
BREATHER ASSEMBLY .................................................... 48
Description ................................................................ 48
Inspection .................................................................. 48
CRANKCASE COVER ................................................ 48-50
Description .......................................................... 48-49
Inspection .................................................................. 49
Governor Gear Installation ........................................ 49
Crankcase Cover Installation ................................ 49-50
OPTIONAL OIL FILTER...................................................... 49
LOW OIL PRESSURE SYSTEM .................................... 49-50
SECTION 13: TROUBLESHOOTING ................ 52-53
SPECIFICATIONS .............................................. 54-59
2
DIMENSIONS AND FEATURES
SMALL FRAME ENGINES
ENGINE MODEL DESCRIPTION
GN190H 60 Hz “XL” style, tapered shaft
GN190H Keyed 3/4” unthreaded straight shaft
GN190RV Vertical tapered shaft
GN191H 60 Hz “XE” or “XL” style, no oil filter
GN191H 3/4” straight shaft (SAE J609a)
GN191H 3/4” keyed straight shaft
GN191RV Vertical tapered shaft
GN220H Horizontal tapered shaft
GN220H 3/4” straight shaft
GN220H 1” straight shaft
GN220H 3/4” keyed straight shaft
GN220H 5/8” threaded straight shaft
GN220RV No governor parts; for use in computer controlled generators
If you don't understand any portion of this manual, contact
an authorized Generac service dealer.
Throughout this publication, 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.
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 handling,
installing, operating or servicing instructions that,
if not strictly complied with, may result in personal
injury.
In addition to the DANGER, WARNING, CAUTION and NOTE
blocks, the following blocks indicate specifications or capacities as noted.
Indicates a fluid capacity.
Indicates a measurement.
Indicates a torque specification.
Indicates a load specification.
CAUTION: After this heading you can read instructions for handing, 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.
3
DIMENSIONS AND FEATURES
GENERAC
PTO SIDE VIEW
BOTTOM VIEW — MOUNTING HOLES
4
/
FRONT VIEW
DIMENSIONS AND FEATURES
5
DIMENSIONS AND FEATURES
GENERAC
STARTER SIDE VIEW
PTO CRANKSHAFT OPTIONS VIEW
6
CUTAWAY VIEWS
DIMENSIONS AND FEATURES
ITEM DESCRIPTION ITEM DESCRIPTION
1 CRANKCASE
2 CRANKCASE COVER
3 CYLINDER HEAD
4 CRANKSHAFT
5 CAMSHAFT
6 ROCKER COVER / BREATHER
7 CONNECTING ROD
8 PISTON RING SET
9 OIL PICK-UP ASSEMBLY
10 CRANKCASE COVER GASKET
11 PISTON
12 PISTON PIN
13 SNAP RING
14 TAPPET
15 PUSH ROD
16 OIL PUMP
17 CYLINDER HEAD GASKET
18 CRANKCASE COVER BOLT
19 ROCKER COVER GASKET
20 CYLINDER HEAD BOLT
21 ROCKER COVER SCREW
22 SPRING WASHER
7
4-CYCLE ENGINE THEORY
GENERAC
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.
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.
C
IGNITION AND
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.
POWER
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.
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.
8
Purpose and Scope of Manual
This manual contains all information normally required to
service or repair the Models GN-190, GN-191 and GN-220
horizontal shaft engines. Applicable procedures are carefully
explained and illustrated.
For exploded views and listings of engine parts, refer to the
Owner's Manual for the specific device on which the engine
is used.
When ordering parts, always include the model and serial
number of the engine. Be sure to insist on genuine Gen-
erac repair parts.
NOTE: Engine Models GN-190RV, GN-191RV and GN220RV (Engine block Part Numbers 86923, 90993 and
90306, respectively) are vertical shaft long blocks. They
are used in Generac's computer controlled, variable
speed RV generator set. Service and repair information
for these vertical shaft long blocks is not included in this
manual. For specific information on these engines, refer
to "SERVICE MANUAL- COMPUTER CONTROLLED VARIABLE SPEED RV GENERATORS," Part No. 94468-A.
SECTION 1: GENERAL
Figure 1.1 — Typical Long Block
Small Frame Engines
Engine Models GN-190, GN-191 and GN-220 are designated as "small frame" engines. The CHART on Page 3 lists
most engine models that were available at the time this
manual was published. Some of the differences between
specific engine models listed in the CHART are as follows:
1.Differences in the type of crankshaft
a. Some engine models may be equipped with a tapered
crankshaft.
b. Some models may have an unthreaded and keyed 3/4
or 1 inch crankshaft.
c. A 5/8 inch diameter threaded crankshaft is used on
some engines.
2.Some engine models are equipped with automatic idle
control, other models are not.
3.Some models may have an oil filter, others may not be so
equipped.
Long Block
The term "long block" refers to a basic engine which does
not include such items as a blower housing, air cleaner, carburetor, etc. Figure 1.1 shows a typical engine long block.
Figure 1.2 shows a typical complete engine.
Figure 1.2 — Typical Complete Engine
Engine I.D. Number/Serial Number
The part number and serial number of the engine long block
can be found on a nameplate, located on the engine crankcase
(see Figure 1.3).
Figure 1.3 — Location of Part and Serial Numbers
9
SECTION 1: GENERAL
GENERAC
ENGINE CARE
RECOMMENDED FUELS:
Use clean, fresh, UNLEADED regular grade gasoline.
Unleaded gasoline burns cleaner, extends engine life and
promotes easier starting by reducing combustion chamber
deposits.The use of gasohol is NOT recommended. If gasohol must be used, it should contain not more than 10 percent
ethanol. If gasohol containing ethanol is used, special care
is required when preparing the engine for storage (see "Storage Instructions").
• DO NOT USE GASOLINE CONTAINING METHANOL.
• DO NOT MIX OIL WITH THE GASOLINE.
DANGER! GASOLINE IS EXTREMELY FLAMMABLE,
AND ITS VAPORS ARE EXPLOSIVE. DO NOT PERMIT
SMOKING, OPEN FLAME OR HEAT IN THE VICINITY
WHILE HANDLING GASOLINE. AVOID SPILLAGE OF
GASOLINE ON A HOT ENGINE. COMPLY WITH ALL
LAWS PERTAINING TO THE STORAGE AND HANDLING OF GASOLINE.
RECOMMENDED ENGINE OIL:
Use a clean, high quality, detergent oil classified "For Service SC, SD, SE, SF or SG." No special additives should be used
with the recommended oil. Detergent oils keep the engine
cleaner and retard the formation of gum and varnish deposit.
Synthetic oil can be used in place of petroleum based oils.
During summer months (above 32 F or 0 C), use SAE 30
oil. SAE 10W-30 oil is an acceptable substitute.
During winter (below 32 F or 0 C) use SAE 5W-20 or 5W30 oil.
• DO NOT USE SAE 10W-4O OIL.
CRANKCASE OIL CAPACITY
GN190, GN191, GN220 ENGINES
WITHOUT OIL FILTER CHANGE —
21 ounces (620 ml)
WITH OIL FILTER CHANGE —
29.5 ounces (870 ml)
CHANGE OIL FILTER:
Replace oil filter with every oil change. Before installing a
new oil filter, put a light coat of clean oil on rubber o-ring on
filter base. Screw the filter on by hand until o-ring touches
filter adapter base,then tighten 3/4 turn. Check for leaks after
starting.
Check engine oil level each time the equipment is used.
When checking oil level, make sure the equipment is level.
Change oil after the first eight hours of operation on a new
engine. Thereafter, change oil and filter every 50 hours of operation. Change oil ever
y 25 hours if operating under extremely
dusty or dirty conditions, or in very hot weather.
NOTE: Engine may be equipped with automatic low oil
shutdown capability. If so equipped, it will not start
when oil level is low. See Section 12, "Lubrication."
STORAGE INSTRUCTIONS
The engine should be started at least once every seven days
and allowed to run for at least 30 minutes. If this cannot be
done and the engine is to remain unused longer than 30
days, it must be prepared for storage.
DANGER ! NEVER STORE THE ENGINE WITH FUEL
IN TANK INDOORS OR IN ANY ENCLOSED, POORLY
VENTILATED AREA WHERE FUEL VAPORS MIGHT
REACH AN OPEN FLAME (AS ON A FURNACE,
WATER HEATER, DRYER, ETC.). FIRE OR AN EXPLOSION COULD RESULT.
To prepare an engine for storage, proceed as follows:
1.Run the engine for about five minutes to warm it up.
a. If gasohol was used, drain the fuel tank, then run the
engine until it shuts down due to lack of fuel.
b. Use of a good fuel stabilizer will prevent gum deposits
from forming in the engine fuel system.
2.While engine is still warm from running, drain oil from
crankcase and refill with new oil.
3.Remove the spark plug and pour about 1/2 ounce (15ml)
of clean, fresh engine oil into cylinder. Crank the engine
over slowly to distribute the oil. Then, install spark plug but
do not connect the spark plug wire.
4.Clean dirt, oil, grease, etc., from the engine.
5.Store the engine in a clean, dry area.
TUNE-UP PROCEDURE
Following is a minor tune-up procedure. When the procedure has been completed, either the engine will run properly
or further repairs may be required.
1.Service or replace engine air cleaner as needed.
2.Check level and condition of oil. Add or change oil
as necessary.
3. Remove the blower housing. Clean dirt from intake screen,
head and cylinder cooling fins. Also, remove dirt from carburetor and governor lever(s) and linkage.
4.Clean fuel tank, fuel filter(s) and fuel lines.
5.Replace any damaged governor springs.
6.If required, adjust the carburetor and governor.
10
SECTION 1: GENERAL
7.Replace the spark plug. Use a Champion RC12YC (or
equivalent) spark plug.
a. Set spark plug gap to 0.030 inch (0.76mm).
b. Install new plug, tighten to 13 ft-lbs (156 in-lbs).
c. If torque wrench is not available, tighten plug with fin-
gers. Then, tighten NEW plug 1/2 turn further; or USED
plug 1/4 turn further.
8.Check that ignition wires are free of breaks and abrasions
and are properly routed.
9.Install the blower housing.
10. Run engine and adjust engine speed.
Figure 1.4 — Exploded View — Typical Horizontal Shaft Long Block
ITEM DESCRIPTION QTY ITEM DESCRIPTION QTY
1 Control Rod Assembly 1
2 Piston Pin 1
3 Piston Ring Set
4 Gear Cover Assembly 1
5 M8 x 52mm Head Bolt 5
6 Piston 1
7 Pin Retainer Ring 2
8 Crankshaft Assm. 1
9 Governor “R” Pin 1
10 Gov. Arm Thrust Washer 1
11 Crankcase Assembly. 1
11B Crankcase Assembly. 1
12 Governor Arm 1
13 Oil Seal 2
14 Governor Gear Assembly 1
15 Governor Gear C-Ring 1
16 Governor Spool 1
17 1/8” NPT Pipe Plug 1
18 Camshaft Assembly 1
19 Crankcase Gasket 1
20 Valve Stem Seal 1
21 Cylinder Head Gasket 1
22 Oil Pressure Relief Cover 1
23 Oil Pressure Spring 1
24 11/32” Ball 1
1
25 M5 Form Screw 1
26 M6-1.0 x 12mm Screw 4
27 Gov. Gear Thrust Washer 1
28 M8-1.25 x 35mm Screw 6
29 Spring Washer 1
30 Valve Spring Retainer 2
31 Valve Spring 2
32 Valve Spring Wear Washer 2
33 Geroter Set 1
34 “O” Ring 1
36 Cylinder Head Assembly 1
37 Exhaust Valve 1
38 Intake Valve 1
39 Push Rod 2
40 Tappet 2
41 Oil Pick-up Assembly 1
42 Rocker Cover Gasket 1
43 Pivot Ball Stud 2
44 GN-190/220 Rocker Arm 2
45 Rocker Arm Jam Nut 2
46 Push Rod Guide Plate 1
47 1/4” NPT Pipe Plug 2
48 Rocker Cover Assembly 1
49 Plastic Oil Fill Plug 1
11
SECTION 1: GENERAL
GENERAC
OVERSIZE PARTS
GENERAL:
At the time this manual was published, oversize pistons,
rings, valves, etc., were not available. Worn or damaged
parts must be replaced.
OVERSIZE PISTONS AND RINGS:
Oversize pistons and rings are not available at this time. The
engine cylinder cannot be rebored to an oversize dimension.
If the cylinder is worn excessively or damaged, the crankcase
must be replaced. A standard size piston and rings can then
be used.
OVERSIZE VALVES:
Oversize valves are not available at this time. Valve guides
cannot be rebored to an oversize dimension. If valve guides
are worn or damaged, the cylinder head must be replaced.
Standard size valves can then be used. Valve guides cannot
be replaced.
NOTE: Always use original GENERAC® replacement
parts.
12
NOTES
13
SECTION 2: AIR CLEANERS AND CARBURETION
GENERAC
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.
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 precleaner into the cover.
6.Insert the paper filter into the cover so it holds the precleaner in place.
7.Assemble the pre-cleaner, paper filter and cover to the air
cleaner base.
AIR CLEANER BOX REMOVAL:
If the air cleaner box must be removed for further engine
disassembly, do the following (see Figure 2.2):
1.Remove the air cleaner cover.
2.Remove the foam pre-cleaner and paper filter.
3. Remove the choke knob (units with choke style carburetor).
4.Remove the breather hose.
5.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.
CAUTION! Removal of the two phillips head screws
on a choke style carburetor/air cleaner box combination 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.
Figure 2.1 — Typical Air Cleaner
PAPER FILTER:
1.Remove the air cleaner cover.
2.Remove the foam pre-cleaner and service it, if necessary.
14
BREATHER HOSE
CAP SCREW
PAPER FILTER
GASKET
FOAM
AIR CLEANER BOX
PHILLIPS HEAD SCREWS
PRE-CLEANER
Figure 2.2 — Removal of Air Cleaner Box,
Primer Style Carburetor
BREATHER HOSE
CAP SCREW
PAPER FILTER
GASKET
CHOKE KNOB
AIR CLEANER BOX
PHILLIPS HEAD SCREWS
FOAM
PRE-CLEANER
Figure 2.3 — Removal of Air Cleaner Box,
Choke Style Carburetor
AIR CLEANER BOX INST
ALLATION:
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 phillips head
screws (see Figure 2.2). If reinstalling the air cleaner box
with a choke style carburetor, line up the holes of the carburetor and air cleaner box with the holes on the intake
manifold before installing the phillips head screws (see
Figure 2.3). Refer to “Torque Specifications” on page 59
for proper torque.
2. Install the cap screw in the upper part of the air cleaner box.
Refer to Torque Specifications on page 59 for proper torque.
3.Reinstall the breather hose.
4. Reinstall the choke knob (units with choke type carburetor).
5. Install the filters and cover as stated in the preceding sections
on filter maintenance.
SECTION 2: AIR CLEANERS AND CARBURETION
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 storage 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 in most automotive repair
facilities or in lawn and garden centers.
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.
ADJUSTABLE AND FIXED MAIN JET:
Some early production GN series engines were equipped
with a carburetor having an adjustable main jet. On later production engines, a carburetor with fixed main jet is used.
Figure 2.4 — Typical Carburetor with Primer
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 servicing any carburetor, be sure to check for evidence of these
conditions.
Figure 2.5— Typical Carburetor with Choke
15
SECTION 2: AIR CLEANERS AND CARBURETION
GENERAC
CARBURETOR REMOVAL:
A choke style carburetor will already be loosened from its mount
following step 5 in “AIR CLEANER BOX REMOVAL” on page 14.
For primer style carburetor, remove the two screws that hold
it to the intake manifold, being careful not to drop the lock
nuts and washers on the opposite ends of the screws (see
Figure 2.6).
The governor rod and lash spring must now be detached
from the throttle rod on either style of carburetor. Simply tilt
the carburetor until the rod and spring can slip out of the hole
on the lever.
GOVERNOR ROD
AND ANTI-LASH SPRING
SCREWS
GASKET
LOCK NUT
AND WASHER
CARBURETOR
Figure 2.6 — Removal of Primer Style Carburetor
CARBURETOR DISASSEMBL
Y:
See Figure 2.7. The carburetor can be disassembled
as follows:
1.Remove the BOWL NUT (Item 4) and the FIBER WASHER
(Item 5). Then, remove the FLOAT BOWL (Item 3).
2.Remove the FLOAT PIN (Item 7). Then, remove the FLOAT
(Item 2) and INLET VALVE (Item 8).
3.Remove the IDLE SPEED SCREW (Item 18) along with
SPRING (Item 17).
4.Rotate the THROTTLE VALVE (Item 14) to its closed posi-
tion and remove the SCREW (Item 13). The THROTTLE
VALVE can now be removed.
5.Remove the THROTTLE SHAFT (Item 15), along with the
THROTTLE SHAFT SPRING (Item 12) and the THROTTLE
SHAFT SEAL (Item 11).
CLEANING AND INSPECTION:
1. Separate out all nonmetallic parts. Then, clean metallic parts
with solvent or commercial carburetor cleaner. DO NOT
ALLOW NONMETALLIC PARTS TO CONTACT SOLVENT.
2.Inspect the THROTTLE SHAFT (Item 15) and THROTTLE
VALVE (Item 10). Replace if damaged.
3.Inspect the IDLE JET (Item 16). Check the passages as well
as its seating surface for damage. Replace if worn, damaged or defective.
4. If so equipped, inspect the MAIN JET ADJUSTMENT. Replace,
if necessary.
NOTE: Later production carburetor may not be equipped
with a MAIN JET ADJUSTMENT:
5.The FLOAT BOWL (Item 3) must be free of dirt and corrosion. Use a new gasket when assembling the FLOAT BOWL.
NOTE: The float setting is FIXED and NONADJUSTABLE.
6.Replace the FLOAT (Item 3) if necessary.
7.After cleaning metal parts in cleaner, blow out all carburetor passages with compressed air.
DO NOT ALLOW CARBURETOR METAL PARTS TO SOAK
FOR LONGER THAN 10 MINUTES OR THEY MAY BE
DAMAGED.
NEW STYLE, NONADJUSTABLE TYPE EMISSION
CARBURETOR
Generac recognizes that there are spray type carburetor 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: 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 INSTALLATION:
To reinstall a primer style carburetor, line up the mounting
holes on the carburetor with the holes on the intake manifold and install the two screws. Then install the lock nuts and
washers onto the screws (see Figure 2.6).
To reinstall a choke type carburetor, see Step 1 under AIR
CLEANER BOX INSTALLATION on Page 15.
Refer to TORQUE SPECIFICATIONS on Page 59 for proper
tightness of carburetor and air box screws.
NOTE: Always use a new gasket when reinstalling the
carburetor and/or air cleaner box.
16
SECTION 2: AIR CLEANERS AND CARBURETION
ITEM QTY DESCRIPTION ITEM QTY DESCRIPTION
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
Figure 2.7 — Exploded View of Typical Carburetor
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
17
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