Generac Power Systems GN190H Installation and operating manual

FOREWORD
This manual has been written and published by GENERAC®
POWER SYSTEMS, INC. to aid our dealers’ mechanics, company serv-
ice 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, 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 trou-
bleshooting, 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 proce-
dure or method. We have not undertaken any such wide evaluation.
Therefore, anyone who uses a procedure or method not recom-
mended by the manufacturer must first satisfy himself that neither
his safety, nor the product’s safety, will be endangered by the serv-
ice 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.

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

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
TABLE OF CONTENTS
GENERAC

3
DIMENSIONS AND FEATURES
If you don't understand any portion of this manual, contact
an authorized Generac service dealer.
Throughout this publication, DANGER, WARNING and CAU-
TION blocks are used to alert you to special instruction about
a particular operation that may be hazardous if performed incor-
rectly 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, CAU-
TION and NOTE blocks found throughout the manual.
DANGER: After this heading you can read han-
dling, installing, operating or servicing instructions
that, if not strictly complied with, will result in per-
sonal 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.
CAUTION: After this heading you can read instruc-
tions 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.
In addition to the DANGER, WARNING, CAUTION and NOTE
blocks, the following blocks indicate specifications or capaci-
ties as noted.
Indicates a fluid capacity.
Indicates a measurement.
Indicates a torque specification.
Indicates a load specification.
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

4
DIMENSIONS AND FEATURES
GENERAC
PTO SIDE VIEW
BOTTOM VIEW — MOUNTING HOLES

5
DIMENSIONS AND FEATURES
/
FRONT VIEW

6
DIMENSIONS AND FEATURES
GENERAC
STARTER SIDE VIEW
PTO CRANKSHAFT OPTIONS VIEW

7
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
CUTAWAY VIEWS

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.
AINTAKE
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 atmos-
pheric 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.
BCOMPRESSION
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 com-
pressed. 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.
DEXHAUST
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.
8
4-CYCLE ENGINE THEORY
GENERAC