Generac 410 User 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 ................................ 9

LARGE FRAME ENGINES .................................................. 9

LONG BLOCK .................................................................. 9

ENGINE I.D. NUMBER/SERIAL NUMBER ............................ 9

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 .......................................................... 15-16

General...................................................................... 15

Common Carburetor Problems .................................. 15

Carburetor Removal .................................................. 15

Carburetor Disassembly ........................................ 15-16

Carburetor Cleaning and Inspection .......................... 16

Carburetor Reassembly .............................................. 16

Carburetor Installation .............................................. 16

CARBURETOR ADJUSTMENT .......................................... 17

Initial Adjustment ...................................................... 17

Final Adjustment........................................................ 17

SECTION 3: MECHANICAL GOVERNOR.......... 18-20

GOVERNOR OPERATION ................................................ 18

GOVERNOR INTERNAL PARTS ........................................ 18

GOVERNOR EXTERNAL PARTS .................................. 18-19

Without Automatic Idle Control ................................ 18

With Automatic Idle Control ...................................... 19

Removal of Governor External Parts .......................... 19

Installation of Governor External Parts ........................ 19

GOVERNOR GEAR SHAFT REPLACEMENT ...................... 19

Inspection .................................................................. 19

Removal .................................................................... 19

Installation ................................................................ 19

LINKAGE INSTALLATION ................................................ 20

GOVERNOR ADJUSTMENT ........................................ 20-21

Initial Adjustment ...................................................... 20

Running Adjustment ............................................ 20-21

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 .................................. 22-23

General...................................................................... 22

Initial Adjustment.................................................. 22-23

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

Valves ........................................................................33

Valve Seats ................................................................ 33

Valve Tappets ............................................................ 34

Valve Springs.............................................................. 34

Valve Guides.............................................................. 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 .......................................................... 39-40

General...................................................................... 39

Description .......................................................... 39-40

Ring End Gap ............................................................ 40

CONNECTING ROD ........................................................ 40

ASSEMBLY AND INSTALLATION ...................................... 41

Assembly .................................................................. 41

Installation ................................................................ 41

CYLINDER SERVICE ........................................................ 41

Inspection .................................................................. 41

Reboring the Cylinder ................................................ 41

SECTION 11: CRANKSHAFT, CAMSHAFT

AND BALANCER .............................................. 42-45

CRANKCASE COVER REMOVAL .................................... 42

CRANKSHAFT, CAMSHAFT AND BALANCER REMOVAL .. 42

BALANCER INSPECTION ................................................ 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

BALANCER INSTALLATION .............................................. 45

SECTION 12: LUBRICATION ............................ 46-51

GENERAL ...................................................................... 46

OIL FLOW ...................................................................... 46

OIL PICKUP ASSEMBLY .............................................. 46-47

Description ................................................................ 46

Inspection .................................................................. 47

OIL PUMP ...................................................................... 47

Description ................................................................ 47

Inspection .................................................................. 47

PRESSURE RELIEF VALVE ................................................ 48

Description ................................................................ 48

Inspection .................................................................. 48

CRANKSHAFT OIL SEALS ................................................ 48

Description ................................................................ 48

Seal Replacement ...................................................... 48

BREATHER ASSEMBLY .................................................... 49

Description ................................................................ 49

Inspection .................................................................. 49

CRANKCASE COVER ................................................ 49-50

Description ................................................................ 49

Inspection .................................................................. 49

Governor Gear Installation ........................................ 49

Crankcase Cover Installation ................................ 49-50

OPTIONAL OIL FILTER...................................................... 51

LOW OIL PRESSURE SYSTEM .......................................... 51

SECTION 13: TROUBLESHOOTING ................ 52-54

SPECIFICATIONS .............................................. 55-61

2

DIMENSIONS AND FEATURES

If you don't understand any portion of this manual, con-

tact 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

STARTER SIDE VIEW

5

DIMENSIONS AND FEATURES

GENERAC

PTO CRANKSHAFT OPTIONS VIEW

55. DOWEL PIN

56. DOWEL PIN

57. SPRING PIN

58. OIL PUMP INNER ROTOR SHAFT

59. CAMSHAFT GEAR

60. ROCKER ARM

61. COMPRESSION RELIEF SPRING

62. COMPRESSION RELIEF FLYWEIGHT

63. COMPRESSION RELIEF LIFT SHAFT

64. O-RING

65. VALVE SPRING RETAINER

66. VALVE SPRING KEEPER

67. EXHAUST VALVE

68. INTAKE VALVE

69. DOWEL PIN

70. VALVE SPRING WEAR WASHER

71. VALVE SPRING

37. CRANKSHAFT GEAR

38. CRANKSHAFT OIL SEAL

39. PIVOT BALL STUD

40. JAM NUT

41. CRANKSHAFT GEAR

42. OIL PRESSURE RELIEF SCREW

43. OIL FILL PLUG

44. TAPER PLUG

CUTAWAY VIEWS DESCRIPTIONS

19. OIL PUMP OUTER ROTOR

20. OIL PUMP INNER ROTOR

21. CYLINDER HEAD GASKET

22. CRANKCASE COVER BOLT

23. ROCKER ARM COVER GASKET

24. CYLINDER HEAD BOLT

25. DATA DECAL

26. OVERLAMINATE

45. TAPER PLUG

46. GOVERNOR GEAR THRUST WASHER

47. GOVERNOR FLYWEIGHT PIN

48. OIL PICKUP ASSEMBLY

49. GOVERNOR RETAINER CLIP

50. GOVERNOR ARM “R” PIN

51. GOVERNOR ARM THRUST WASHER

52. VALVE STEM SEAL

27. ROCKER ARM COVER SCREW

28. SPRING WASHER

29. OIL PRESSURE RELIEF VALVE SPRING

30. OIL PRESSURE RELIEF VALVE BALL

31. GOVERNOR SPOOL

32. GOVERNOR GEAR

33. GOVERNOR FLYWEIGHT

34. GOVERNOR SHAFT

53. OIL PRESSURE RELIEF RETAINER

54. PUSH ROD GUIDE PLATE

35. GOVERNOR ARM

36. PIPE PLUG

6

1. CRANKCASE

2. CRANKCASE COVER

3. ASSEMBLY

4. CRANKSHAFT

5. CAMSHAFT

6. ROCKER ARM COVER

7. CONNECTING ROD

8. PISTON RING TOP

9. PISTON RING, SECOND

10. OIL RING, RAIL

11. OIL RING, SPACER

12. BALANCER

13. CRANKCASE COVER GASKET

14. PISTON

15. PISTON PIN

16. SNAP RING

17. TAPPET

18. PUSH ROD

CUTAWAY VIEWS

7

DIMENSIONS AND FEATURES

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.

IGNITION AND

C

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-320, GN-360 and GN-410
horizontal shaft engines. Repair procedures are carefully
explained and illustrated.

LARGE FRAME ENGINES

Engine Models GN-320, GN-360 and GN-410 are desig­nated as "large frame" engines. Some of the differences
between specific engine models are as follows:

1.Differences in the type of crankshaft.

a. Some engine models are equipped with a tapered crank-

shaft.

b. Some engine models may be equipped with a 1-inch

straight shaft.

2.Some engine models are equipped with automatic idle

control, other models are not.

3.Some engine models are equipped with an OPTIONAL oil

filter assembly.

4.Some engines may be equipped with electric start, others

are manual start.

5.Some engine models are "vertical shaft" for use in specific

applications (such as recreational vehicle generators).

6.Some engines are "horizontal shaft" type.

7.Some have an LOS (Low Oil Shutdown) module.

8.Some have an oil fill tube.

SECTION 1: GENERAL

Figure 1.1 — Typical Long Block

LONG BLOCK

The term "long block" refers to a basic engine which does
not have such items as a blower housing, air cleaner, carbu­retor, etc. Figure 1.1 shows a typical long block.

Figure 1.2 shows a typical complete engine, with all the parts
needed to adapt the engine for a particular use. The typical
complete engine shown is a horizontal shaft model, for use
with AC generators.

ENGINE I.D. NUMBER/SERIAL NUMBER

The engine ID number and serial number of the engine long
block can be found on a nameplate, located on the engine
crankcase. (See Figure 1.3).

NOTE: Have the engine model and serial number when
ordering parts. This number is located on the back of
the cylinder block on the identification tag.

Figure 1.2 — Typical Complete Engine

Figure 1.3. — Location of Engine I.D. 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 SPILL AGE
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 base oils.

During summer months (above 32F or 0C), use SAE 30 oil.
SAE 10W-30 oil is an acceptable substitute.

During winter (below 32F or 0C) use SAE 5W-20 or 5W­30 oil.

DO NOT USE SAE 10W-4O OIL.

CRANKCASE OIL CAPACITY
GN-320, GN-360, GN-410 ENGINES
WITHOUT OIL FILTER CHANGE —
46 ounces (1350 ml)
WITH OIL FILTER CHANGE —
51 ounces (1500 ml)

CHANGE OIL FILTER:

Replace oil filter with every oil change. Before installing new
oil filter, put a light coat of clean oil on rubber o-ring on filter
base. Screw filter on by hand until o-ring touches filter
adapter base, then tighten 3/4 turn. Check for leaks after start­ing engine.

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 the 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 Connecting Rod Assembly 1
2 Piston Pin 1
3 Piston Ring Set 1
4 Piston 1
5 Snap Ring 2
6 Crankshaft Assembly 1
7 Governor Arm 1
8 Governor Arm “R” Pin 1

9 Governor Arm Washer 1
10 Crankcase Assembly 1
11 Sleeve Bearing 1
12 Crankshaft Oil Seal 2
13 Governor Gear Assembly 1
14 Governor Gear Retainer 1
15 Governor Spool 1
19 Camshaft Assembly 1
20 Crankcase Gasket 1
21 Cylinder Head Gasket 1
22 Oil Pressure Relief Retainer 1
23 Oil Pressure Relief Spring 1
24 Oil Pressure Relief Ball 1
25 Governor Thrust Washer 1
26 Crankcase Cover 1
27 Valve Spring Retainer 2
28 Valve Spring 2

29 Gerotor Set 1
30 Balancer 1
31 Cylinder Head Assembly 1
32 Exhaust Valve 1
33 Intake Valve 1
34 Push Rod 2
35 Tappet 2
36 Oil Pick-up Assembly 1
37 Rocker Cover Gasket 1
38 Pivot Ball Stud 2
39 Rocker Arm 2
40 Rocker Arm Jam Nut 2
41 Push Rod Guide Plate 1
42 Cylinder Head Bolt 4
43 Rocker Cover/Breather Assembly 1
44 Oil Fill Plug 1
46 “O” ring 1
47 Pipe Plug 2
48 Oil Pressure Relief Screw 1
50 Valve Spring Keeper 4
51 Rocker Cover Screw 4
52 Crankcase Cover Bolt 8
53 Valve Stem Seal 1
54 Valve Spring Wear Washer 2

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

SECTION 2: AIR CLEANERS AND CARBURETION

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.

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.

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 con­nected to the Low Oil Indicator and Start/Stop switch.

Figure 2.1. Typical Air Cleaner

APER FILTER:

P

1.Remove the air cleaner cover.

2.Remove the foam pre-cleaner and service it, if necessary.

3.Remove the paper filter.

13

BREATHER HOSE

GASKET

AIR CLEANER BOX

NUT AND WASHER

PAPER FILTER

FOAM

CHOKE KNOB

NUT, WASHER
AND LOCK WASHER

CAPSCREW
AND WASHERS

PRE-CLEANER

Figure 2.2 — Exploded View of Air Cleaner Box

SECTION 2: AIR CLEANERS AND CARBURETION

GENERAC

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 2.2). Refer to “Torque Specifications” on page
59 for proper torque.

Note: 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 2.2).

2. Install the two capscrews in the lower part of the air cleaner
box (see Figure 2.2). Refer to Torque Specifications on page
61 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 ser­vicing 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 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.

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 CLEANER

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.

GOVERNOR
ROD AND
ANTI-LASH SPRING

CARBURETOR
MOUNTING
BOLT

CARBURETOR
GASKET

CARBURETOR

Figure 2.3 — Removal of Carburetor

CARBURETOR DISASSEMBL

Y:

To disassemble the carburetor, proceed as follows (See
Figure 2.4):

1.Remove the FLOAT BOWL NUT (Item 1) and the FIBER

WASHER (Item 2). Then remove the FLOAT BOWL (Item 3).

2.Remove the FLOAT PIN (Item 4). Then remove the FLOAT

(Item 5), and FUEL INLET VALVE (Item 6).

3.Remove the IDLE SPEED STOP SCREW (Item 16) along with

its SPRING (Item 17).

4.Rotate the THROTTLE PLATE (Item 8) to it's closed position

and remove two THROTTLE PLATE SCREWS (Item 7).

14

SECTION 2: AIR CLEANERS AND CARBURETION

5.Rotate the CHOKE PLATE (Item 14) to its closed position
and remove the CHOKE RETAINER SPRING (Item 15).

6.Remove the CHOKE SHAFT (Item 12) and the CHOKE
SHAFT SEAL (Item 13).

7.Remove the THROTTLE SHAFT (Item 11) and the THROT­TLE SHAFT SEAL (Item 10).

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 (Item 11) Replace if worn or
damaged.

3. Inspect the CHOKE SHAFT (Item 12) Replace if worn or dam­aged.

4.Inspect the FLOAT BOWL (Item 3). It must be free of dirt
and corrosion.

5.Inspect the FLOAT (Item 5) Replace if damaged.

6.After all metallic parts have been cleaned, blow out car­buretor passages with compressed air.

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.

ITEM QTY DESCRIPTION
1 1 Float Bowl Nut
2 1 Fiber Washer
3 1 Float Bowl
4 1 Float Pin
5 1 Float
6 1 Fuel Inlet Valve
7 2 Throttle Plate Screw
8 1 Throttle Plate
9 1 Carburetor Body
10 1 Throttle Shaft Seal
11 1 Throttle Shaft
12 1 Choke Shaft
13 1 Choke Shaft Seal
14 1 Choke Plate
15 1 Choke Retainer Spring
16 1 Idle Speed Stop Screw
17 1 Spring

Figure 2.4 — Exploded View of Carburetor

CARBURETOR REASSEMBLY:

Reassemble the carburetor in the reverse order of disas-

sembly. 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 Figure 2.4).

3.The FLOAT SETTING is FIXED and NONADJUSTABLE.

4. Before tightening the FLOAT BOWL NUT (Item 1), make sure
the FLOAT BOWL is properly aligned with the GASKET and
the CARBURETOR BODY.

CARBURETOR INST

ALLATION:

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.”

15

SECTION 2: AIR CLEANERS AND CARBURETION

GENERAC

CARBURETOR ADJUSTMENT

INITIAL ADJUSTMENTS:

(See Figures 2.4 and 2.5)

1.The IDLE SPEED STOP SCREW is located at top of the car­buretor and contacts the THROTTLE SHAFT. After
reassembling 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 accom­plished with the engine running. Engines equipped with
optional automatic idle control require a special proce­dure for idle speed adjustment. See Section 4,
"Optional Idle Control."

NOTE: The carburetor is equipped with a fixed main jet,
which requires no adjustment.

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 4, "Optional Idle Control."

If the engine is used to drive an AC generator set, use an
AC frequency meter to measure engine speed/frequency.
Connect 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 idle speed is between 62-63
Hertz. (3720-3780 rpm).

b. If the unit is not a generator, adjust the idle speed stop

screw to obtain about 3750 rpm.

Figure 2.5 — Idle Speed Stop Screw

16

NOTES

17