Generac Power Systems GTV99O, GTV760 Service Manual

Malual Part

No. OE2Oal

fr

SERVICE

MANUAL

F

["J

*.1

POWER

P.O.

Box 297

Phone:

[phone]

P nted

in

lJ.s.A

GiENEFIAC'

SYSTEMS,

INC.

.

Whitewater, Wl . 53190

GTV

-1990/760
V-TWIN

OHVIENGINE

Fax:.

(262)

472-6505

Firsl Edition lssued - bi/xrxx

?J

FOREWORD

This

manualhas been written and

published by e

tHeUC@

pOWe

n

SYSTEMS,

lNc. to aid our dealers' mechanics,

company

servlce

per_

sonneland

general

consumers when servicingthe

products

des(ribed

herein.

It

is assumed

that these

personnelare

familiarwiththe

servi(ing

pro_

cedures

torthese

products,^or like or similar

products,

manu{actured

and

marketed

byGENERAC@

PowER

sYsTEM

s, lNc. lt is alto assumed

that they

have been

trained

in the

recommended

servicing

procedures

for the5e

products, which

includes

the use

of mechanics

hand

tools

and

any specialtools

that might

be

required.

Proper

service

and repair

is imPonant

to the safe,

economical

and

reliable operation

of the

products

de5cribed

h€rein

The trou'

bleshootirlg,

testing,

service

and

rePair

procedures

recommended

by

cEtltnlc@ PowrR

sysTEMs,

lNc. and

described

in this

manual

are

effective

methods

of

performing suah operation5.

Some

ofthese

oper-

ations

or

procedures

may

require

the use

of specialized

equipment'

Such equipment

should

be

used

when and

as recommended

we

(outd

not

possibly

know

oI and

advise

the sewice

trade

of

all

conceivable

pro(edures ot methods

by

which a

service

might

be

per-

formed,

nor

ot any

possible hazards

and/or results

ot each

procedure

ormethod,We

have notundertaken

any

such wideevaluation

There-

{ore, anyone

who

uses a

Procedure

or method

not

recommended

by

the manu{acturer

must {irst

satisly

himselfthat

neither

his sa{ety,

nor

the

product's satety,

will be endangered

by the

service

or oPerating

procedure

selected,

Atl

information,

illustrations

and sPe(ifications

contained

in this

manual

are based

on the

latest

product information

available

at the

iliili

"'tri.n",

However,

GENERAC@

PowER

sYsrEMs,

lNc'

reservesihe

rightto

(hange,

alter

orotherwise

improve

the

product

at any

time

without

Prior

noti(e.

some components

or assemblies

o{

the

Product

degcribed

in this

manuat

may

not be

(onsidered

rePairable.

Disassembly,

repair and

reassembly

oI such

components

may

not be inctuded

in this

manual'

The engines

described

herein

may be used

to

power

a wide

variety

oI Droducts.

Service

and

repair instructions

relating toany

such

prod'

uatsare

notcovered

in this

manual. Forinformation

pertainingto

use

of these

engines

with other

products,

re{erto

any

owne/s

or service

manuals

pertaining

to said

products.

?.,

TABLE OF

CONTENTS

RULES FOR

SAFE OPERATION

DIMENSIONS

AND

FEATURES

4-CYCLE

ENGINE

THEORY

SEcTION

1: GENERAL

INFORMATION

SECTION

2: IGNITION

SECTION 3;

CARBURETION

SECTION

4: GOVERNOR

CONTROLS

AND

GOVERNOR

SECTION

5: CYLINDER

HEAD AND VALVES

SECT|oN

6: El.ECTRlc

SIARIER

SECNON 7:

ALTERNATORS

SECTION 8:

LUBRICATION

SYSTEM

SECTION

9:

ENGINE DISASSEMBLY

SECTION

lO: CYLINDER

AND CRANKCASE

COVER

SECTION

11: CRANKSHAFT

AND CAMSHAFT

SECTION

12: PISTON,

RINGS AND

CONNECTING

ROD INSPECTION

AND

ASSEMBLY

SECTION

13r ENGINE

ASSEMBLY

A WORD ABOUT

SPECIALTOOLS

Many ot

the

prccedurcs

depicted in this manual

rcquite the

use of special

tools. Some of

the tools

reouired are available

as Genetac

patts

and ate

listed as such in

this manual.

ATTENTION!

cenerac

Power Systems

does notapprove orauthorizethe

use ol these

eng ines- on AllTerrain

Vehicles

(AW"s);

go-carts,

motorbikes, aircraft

products,

personal

watercraft,

or vehicles

intended

for use

in

(ompetitive

events. Use

ofthese engines

in such

applications could

result

in

property

damage, serious

injury

(in.luding

paralysis),

ot even

death.

t

RULES

FOR SAFE OPERATION

lfyou

do not understand any

podion

of

this manual, con-

tad Cenerac

or

your

nearest

Generac

Authorized S€rvice

Dealerfor starting, operating and

setulclng

procedures.

Throughoutthis

pubIcilion

and ontags

and decaG affixed

to the

engine, DANGER,

WARNING

and CAUTION blocks

a€ used to aled

you

to speclal instrudion

about;

panicu,

laropefalion that may be hazardous

if

performed

lncorrectly

or carclessly. ObseNe them

carefully.

These safety warnings

cannot eliminate

the

hazards

that

they indicate.

Stict

compliance with

the specialinsVuctions

whrle

per{or"l

ng

the serv

(

p

plLs

'

comaor

.Frse'

ara

majo.

The following definitions

apply io oANGER,

WARNING,

CAUTION and NOTE

blocks found throuqhoutthe

manua

These safety synbols indicate

the follawing:

DANGER: After

lhis heading

you

can read han-

dling, installing,

op€rating

or sewicing instructions

that, if not

rtrictly compiied

with, witt resutt in

personalinjnry

WARNING:

After

this heading

you

can read han-

dling.

installing,

operating or servicing

instructions

that, if notnrictlycompli€d

with,

may result in

per-

sonal injury,

CAUTION: After

this heading you

can read instruc-

tions for

handling, installing,

operating

orservi(ing

the

enginethat, il

not stri.tly

complied wirh, may

result

in damage

to €qu;pnent

and/or

property

NOTE:

After this heading you

<an rcad explanatory

statements

that rcquirc

special emphasis.

These

symbols indicate

the fo lowing:

Points

out important saiety

inlormation that, ilnot

lollowed,

could

endanger

personal

salety and/or

Prope

y

ofyourseli

and others.

RULES FOR SAFE OPERATION

Studythese RIJLES FOR SAFE OPERATION

carefu

y

before

operalinq

or servicing th is equipment. Become familia

r w th

Tfp OWNFR'5 N.4ANUA

adwith

_eergirF

Tl-eengrnecar

operalesa{€ly,

efficiently and reliablyonly if it is

properly

oper

ated

and maintained. Many

accrdents ar€ caused

by

failing

to

tolow

simp

e and fundamentalrules

or

precauttons.

Generac

cannot

possiby

anticipate

every

possible

circ!m-

nance

that might involve

a hazard.

The warninqs in

this

manualand

on tags

and decals

affixed tothe

equipmeni, arc

therelore, noi all-inclusive.

tf

you

use a

procedure,

work

method

or operating technique

Generac does notspecifically

recommend, you

must satsfyyoLr6elf

that lt is

safe for

you

and

olhers. You must also make

sLire the

procedlre,

work

method

or operaiing t€chnique

that

you

choose

does not

renderthe

engine to be unsafe.

DANGERT Do not tamper

with the engine

gov-

erned

tpeed. High operating speeds

are dang€rous

and increare

the rhkof

personal

injury

or damag€

to

the equipment. Operating

at low speeds with

heavy load may shorten

the engine's ljfe.

A

Potential

explosion hazard.

A

Potentialfiretrazard.

BEFORE

OPERATING

.

Gaso ine

s highlyFIAMMABLE

and

itsvaporsare

EXPLO-

slVE.

Do not

p€fmlismoklng,

open flames,

sparks or heat

rn

theareawhile handl ng

gasoline.

Avoidspilling

gasoline

on a hot engine.

Comply with all of the

aws regutaiing

storage

and

handling

of

gasol

ne.

.

Slore

gasol

ne and otherfuels

only ln containers

designed

and approved forthe

norage oi such mateials.

.

Add

gaso

in€ in a

clean, welfventlated

area. Wipe up any

spllled

gasollne

immediatey. t gasoline

has been spiled,

let ri dry

completely befo.e startirg

the engine.

.

Do not

ovedi I the luel tank. Alu/ays

alow

room for fuel

expansion ll

the tank is overfilled, the

fuel can ovedlow

onto a hot

engine and cause a FIRE or

an EXPLOSION.

.

Allow

at

lean

two

(2)

feet ofclearance on a lsides

of the

engine, even

wh le operating

it

outdoors. or

you

could

damage trie engrne.

.

Thofoughyinspecttheenqinefor ooseordamagedparts
before each use,

Do

nol usethe

eng ne

unt ladjustments

or Teparfs are

maoe.

.

Check the oll level ln

the engine

before

each use.

A

Pobntial

electricat

shock hazard.

RULESFOR SAFE OPERATION

The engine exhaust lrom

thls

ptoducl

contains

chemicals known to the Stale of Calilornia io

cause cancer,

birth d6fects, or other repro­ductive

harm.

Inspectthe engine

periodically.

Repairor replace all damaged

or defective

parts

immediately.

Inspect

fuel

system

frequently

for leaks or damage.

Repair
or replace any damaged or leaking component immediately,
Never attempt to change, alter or modit the engine fuel
slstem

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 modirythe equipment o. use

itfor any application for which it was not designed.
Generac Power Systems does not approve or authorizethe

use of these engines on

AliTe(ain

Vehicles

(ATV3),go-cads,

motorbikes, alrcraft

pfoducts, personal

watercraft, or vehi­cles intended for use in competitive events. lJse of these
engines in such applications

could

result in

property

damage,

serious

injury

(including

paralysis),

or even death.

Englne exhaust

gases

contain DEADLY

carbon

monoxide

gas-

This dangerous

gas,

lf breathed in

rufficient

concen-

trations,

can cau5e unconsciousness

or even death, Operate
this equipment only in the open air where adequate venti
lation ls available.

Do not insert any object

thrcugh the cooling slots of the

engine. You

could damage the equipmentor injure

yourself.

Do not operate the engine fanerthan ihe 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 coo ing air for its

contrnued

proper

operation. Never

operale the equlpment

inside any room

or enclosure where the free flow ol cool-

ing air into and

outof the equipment might be obnructed.

Withoui sufficienl cooling airilow, the englne

quicklyover-

heats. damaging the engine or nearby

propefty.

Do not smoke around

the engine. Wipe up any fuel or oil

spills rmmediately.

Never leave

oily or fuelsoaked ragsaround

theengine. Keep thearea aroundthe€nglne

clean

andlree

of debrls.
Keep hands, feet, clothing, etc., awayfrom moving

parts

of

this enqine.
Never operate the engine

(a)in

the rain;(b)ln any encosed

compadment;

(c)

if

the engine speed changes;

(d)

if

the

engine spa*s;

(e)

if flame

or smoke s observed while the

engine is running,
Never work on this englne or handle

any e€ctrical device

while

standlng

in water, whie

barefoot, or

while hands

of

feet

arc wet. DANGEROUS ELECTRIC SHOCK wi I result.

SERVICE

INFORMATION

Seruice on this engine

within and atlerthe waffanty

period

can be

pedormed

byanyaulho zedservice

dealer Seruice

iechnicians arc faclorytrained and

capable oi handling all service

needs.

When conlacling an aulhor,zed service dealer aboul
pads

and service.auAys_sllBlflhclgnllgE

nodelnumberand

serialnumber oi

your

unit as

given

on ils dala

plale

decal. Seethe illlstration

below ior the location oi the decal.
The wafianty for this engine is included in the

0wners manuat.

DIMENSIONS AND fEATURES

MODfL

GTV99O

TYPE

I]LCEOLED

4-STREKE

lHV

BORE X STREKF

90 x 7A

DISPLAC

EMENT

99?cc

CBMPRESSlEN

RAT]D

8.5'1

LUBPICAIIIN

SYSTEI.l

rUI

L

PAES-UO]7'D

V/LO\"/

!I . PPE\SLPf

SI.LIIE i

IGNl IIUN

SYSTEI.I

ELICTPDNIC

SPEAKfRLESS

CYL]NDER

CAST IRDN

SLEf VL-

S

IARTING

SYSTEM

ELECTRIC START

IIL CAPACITY

C030ml V/FILTEP,

1750nl V/B

FILTER

VE]GHT

454!a€

/)]Dtbs

DIMENSIONS AND FEATURES

DIMENSIONS AND FEATURES

DIMENSIONS

AND

FEATURES

P,/N OC2965A

P/N OC2955C

P,/N

OC2965t

+CYCLE

ENGINE

THEORY

ftheengine isto

run

properly,

four

(4)

events rnustoccur in

the

proper

sequence and a!the corect time. These

events are

(a)

intake,

(b)

compression,

(c)

ignition

and

power,

and

(d)

exhaust.

A INTAKE

The

piston

is travellinq from top dead center

(IDC)

to bottom

dead center(BDC).

The

cam

has

opened the intake valve. The

piston

s

downward movementin the

cylindercreatesa

partial

vacuurn in the cylinder Air at atmosphefic

pressure

is drawn
into the cylinderthrough the carburetor and is mixed with fuel
in the ca lburetor. The fuel air mixturc flows

thrcugh the open

intake valve into the cylinder When the

piston

reaches BDC,

the intake stoke is over.

C rcNrT|oN

AND

powER

By

the time the

piston

reaches TDC , combustion is akeady

in

progress.

The intake and exhaustvalves remain

closed as the

exprnding

gases

of combustion

force

the

piston

downwad.

D

EXHAUsr

The exhauststroke

beginswhen the

piston

has

rcached BDC

and

has

started its upward movement. The intake

valve is

closed. The exhaunva ve is

open to let

gases

escape.

B

coMPREsstoN

As

the

piston

reaches

bottom de6d

center

(BDC),

both the

intake

and exhaustvalves

are closed. The

piston

moves upward

toward

TDC and

thefuel-air mixture is

compressed.lust before

the

piston

rcaches TDC, ignition

occLirs.

SECTION 1: GENERAL

INFORMATION

SECTION CONTENTS

PAGE

MATNTTNANCE SCHEDULE

.-........................-.......--.......

r-l

FUEL AND OtL RECOMMENDAT|ON5.........-..-.................

1-l

Gasoline

.......................................................

... l-l

Lubrication ..........................................................-.....

l'1

Recomrnended Oi1 Type..............................................

1'1

Chanqe Oi1..................--.............................-.-..........

1-1

Change

Oil Fi|ter..........-..--.......................-.................

1

-2

Cleaning

Intake Scr€en ...........................-.-................

1-2

Replace Spark Plugs .................................................-

1'2

Air C eaner Maintenance

.........-.....-..........................

1_3

Servlce Dual Element

Ai C1eanels..............................

1-3

TROUBLESHOOTTNG

.....................................................

1-4

5y5tematic Check ....--..................,..,,.,.......................

1-4

Check lgnition . .

. . . - . . . . . . . . . . . I

'

check lgnition

(Enqine

Running)..................................

1'

Check lqnition

(Fouled

Pluq of other Caules) ..............

1-

Cylinder

B.

anc.

TFst .......

.... l-

Cre.l Fuer ............. . ....... . .. . ...

... .....

1-

CheckCompression......................................................1_

Cylinder Leakdown

Test ..............................................

1_

Thinqs

Which Affect Both Cylinders ............................

1-

Thing! Which Aff€ct One Cy

lnder

..............................

1'

EQUtpI/tNr

AffEClrNG

ENGtNt OPtoATO\

........ .. ......

Had Startinq orwi

NotStar'1 ............................-....... 1-

EngineWon'tstop......................................................

1-

Vibralion......................................................................

l-

PowerLoss......-...........................................................1-

Noise ..........................................................-............-..1'

NOTE 1 : Change

oil and lller aft€r ilrst 8 hours

ol operation

and

lhen

every 100

hours lhercallsr. Chang€ soonerwhen

opeEtng

under a

heary

load

or

in a dusry or dirty €nvionmenl or in hilh

ambienltemperature.

NOTE

2: Clean mor€ olien when operaling in

didy or dlsiy condillons-

Replace

canlster slyle lilter every 500 hours.

NOTE 3:

Perlorm this lask ONLY afrer lilst 50 hourc

oi op€ration. Head

bolls will NOT need

lunher rclorquing.

FUEL

AND OIt RECOMMENDATIONS

GASOL

NE:

We recommend the use

of clean, fresh lead{ree gasoline.

A rnin-

imumof 85 octane is

recornmend€d. The

use ol eadjree

gasoline

results in

fewercombustion deposits and longer valve life.

Not€: Some fuels, called

oxygenated

or refonulated

gasolines,

arc

gasolines

blended with

alcohols ot etheE.

Ex.essive

amounts of these blends can damage the luel

system

or cause

pertormance prcUem'

Do not use

gaso-

Iine

which contains Methanol. lf any undesirable

operating

swptoms occu|, use

gasoline

with a lower

pe'-

aentage

of alcohol or ethei

It is also recommended

that

gasolin€

be

purchased

in small

quantities,

notmorethan a

30daysupply. FRESH gasollne

min-

imizes

qum

deposits,

and also u/ill ensure fuel volatility

tailored

for the season

in which lhe engine willbe operated.

LUBRCATON:

Oil has four

purposes.

lt cools, ceans, seals

and lubricates.

During nornral operalion,

srnallparticles of metalfromthe

cylin

der

walk,

pistons,

bearings and

combustion

deposits will

gr:dually

contaminate

the oll. Dust

particles

from

the aLr aLso

contaminale the oil

formlng an abrasive mlxture

which can

cause

wear to al of the

nternal moving

pads

of the engine,

lf the

oilis not changed

regulary. Fresh

oilalso assists in cool'

ing. Old oilgradually

becomesthick and loses lts cooling

abi

iq/

as well as

ils lubricatlng

qualities.

RECOMMENDED

O t TYPE:

Using

the

proper

type and

weight of oil in

the crankcise is

extremely

lmportant. Checkthe oilbe{orc

each

use and change

the o

Iregularly(s€e Figures 1-1,

l-2 & 1-3).

Faiurcto

usethe

(o|ecl

o

I.

orLs:19d

-y

oi,

(dr

caJse p emarure

e19i-le

wea'

and

failure.

Use only

high

qua

ry

deterqent

oil rated

w th API s€rvice clas-

siflcatlon

SF, SG or

SH. The recommended oilwelghts

incLude

the

{olowing:

.

During summer

months: SAE 30. An accepta

ble subnitute

is sAE

10w-30. After fi6t oll

change,

syntheric o I G

1,1

MAINTENANCE SCHEDUTE

Every

lElery I

Every

I Houts 125 Hou6 50 Hours

Change OilF

ller

Spa*Plug
Clean Spark

Beloque Head Bo ls

SECTION

1: GENERAL INFORMATION

.

Durinq

winter r.onths

30. DO NOT USE SAE

SAE

5W-30, Synthetic

sW-2

0 or 5W'

10w-40.

F

-2A

a 20

40

60

30 rou

c 30

.20 .10

ro

20

30

Temperature

Fange

or Ev€cted

Us6

CHANGE

OIt:

The cra nkcase oil

capacity is

about 2030

ml

(2.

I

qt

)

with the

oilfilter Withoutthe flfter,

the

oilcapacity

is 1750

ml(1.8

qt.).

Use no special additives.

Makesur€

ihatthe

unit

is everwnen

filling

with oil. DO NOT

OVERFILL.

TMPORTANX

DO NOT

OVERF|LL.

Check

and

maintain oil

level

rcgularly.

Change oit

and fittet

aftet

fi6t eight

(8)

houts

of opetation.

Thereafter,

change oil €nd

filter

every t0O

hou6

oJ opera

tion.

Ch:nge

oil more

often il

enqine i5

operated in

dirty or

dusty

conditionsor

f€n9ine

isoperated

und€r healy

|oaos or

high ambient

a ir

temperatures.

Removeoiidrain pllg

and

drain oitwhite

€ngife

is5r wdrin,

Figure

1-2.

Chanqe

o I fllter

(Figure

t-l)and

reptace

dratn

ptuq

figurc

1-1. o

fill Check

Remove

dipnick

and refitlslow y

w

th new

oilof

proper

5€r

vr.e

classification

and viscosity grade.

R€f I

to fu mark

on

dipstick.

When

check ng

oil evet,

d ipst

ck must

be a ll the way

in

for

accurate

readtngs.

Start

and

run

engine

to check for

oil leaks.

CHANGE

O t FLTER:

Replace

oil f lter

€very I

00 hours.

Befo re nstalt

nq

new I rer,

ightly

oil filter

galket

with

fresh

clean engine oit.

Screw fiier

on by hand

until

gasket

cont.cts

filter adapter

Tighten

3/4 to

one

fullturn

fadher, Fiqure

1-3.

Startand run

engineat idle for

30 seconds and

stop engine.

Recheckoi levelandadd

if required.

Reltartengineandcheck

for

oil

leaks.

figure

1-2. OilDrcin

figure 1-3.

Oil Filter

CLIAN NG INTAKT

SCREEN]

Grass

partices,

chaffor

dirt can clog

the atrcooting

system,

especially

after

prolonqed

service ln

cLjtting dry

grass

or v€ry

driry a r.

Continued

operation with

a cogged

cooling

synem

can

cause severe

overheat ng

and

possible

englne

damage.

Fgure

1 4showsth€arcastobecieaned.Thisshoutdbea

reg-

uar marntenance

operation, or

clean ntake scre€n

and ol

cooler

fins after

each use.

1-2

SECIION

1:

GENERAL

INFORMATION

REPLACE SPARK PLUGS:

Replace

spark

plugs

every 100 hours

of operation or every

season, whichever

occurs first. Replace

spark

plugs

if elec,

trodes are burned

away, orthe

porcelain

is cracked. Setspark

plug gap

at.76

mm

(.030')

for

all models. Torquespark

plugs

to 20.0

Nm

(180

in. ibs_).

Figute 1

-5.

Setting

Spatk

Plug cap

tions are

notcarcfully

followed,

dirtand

dun which

should be

collected in the cleaner, will

be drawn

into

the engine. These

particles

are

highlyabrasive

and willcausethe

plston

rings and

cylinder bore to wear

quickly.

As

the

rings and

cytlnder bore

become worn, these

abrasive

particles

enter

the crankcase

and

contaminate the oil, forming

an abrasive

mixture which

willcause wear

on allof the internal

moving

pads.

The air cleaner on every

engine brcught

in for

a check up

or repair should

be examined and

seNiced. tf

the arr ceaner

shows

signs of

neglect,

show ittothe

customef

berore oean-

ing. Instruct the customer

on

proper

care, to assure long

engine life.

Note: Repla.e ai .leaner

gaskets

and mounting gaskets

that afe wom of damaged. to

prcvent

dirt and dust frcm

entering engine due to imryoper

sealing.

Replace

bent

air

cleaner mounting bracket

if necessary,

SERVICE DUAL

ELEMENTAIR CLEANERS:

Remove and service foam

pre-c

eanerevery

25 hours

orevery

season, wh ichever

occurs firn.setuice

canridge every

50 hou6

or ev€ry

season, whichever occurs first.

SERVCE CAN STER AIR

CLEANERS:

Clean the air filter elemen(s)with

compressed

air every

50

hours or every season, whichever

occurs first.

Replace

the air

{ilter elementG) every 500 hou6

or if damaged.

Note:

The air cleanet assemblies

on some

equipment

may have been supplied by

the equipment

manufa.-

turei

See the equipment manufadurels

owne/s

manual

for seNi.e infomation specili.

to that

prcduct,

TROUBTESHOOTING

lvost compaints

concerning englne

operation

can be clas-

sified as one or a

combination ofthe

followlngi

2. Hard starting

3. Lack ol

power

4. Runs rough

GENERAC

C h

Spark Pluq Type Part

No.

Resistor Plug

AIR CLEANER MANTENANCE:

Vrbration
Overheating

High

oi consumption

472341

RC t2YC

5.

6.

1.

WARNING:

NEVER OPERATE

ENGINE

WITH AIR

CLEANER

ASSEMELY OR

AIR CLEANER

CARTRIDGE

REMOVED.

FIRE MAY RESULT.

A

properly

5erviced air cleaner

protects

lnternalpa(s

of the

enginefrom

dlrtand dun

pa.tic

es in

the air lf aircleaner instruc-

Note: What appears

to be an engine malfunction

may be

a fault of the

powercd

equipment Bthet

than the

engine.

lf equipment is susped,

see equipment

atlecting

engine

Figurc

1-4, Clean lnhke

Sqeen & Oil Coolet Fins

SET PLUG

GAP AT 0.76

mm

t-3

SECTION

.I:

GENERAL INFORMATION

SYSTEMATIC CHECKi

lf the engine will not stad

and the cause

of malfuncrion is

not €adilyapparen!

perform

a systematic

check in the fo lowing

orderl

1. lgnition

2. Fuel

3. Compression
This

check'up,

performed

in

a systematic manneri

cdn usu-

ally be done

in

a matter of minutes.

lt isthe

quickest

and surest

method of determining

the cause of fiilure.

The basiccheckup

procedure

isthe same

for all engine modeh,

while

any

varia-

tion, by model, wiilbe

shown underthe

subject heading.

CHECK IGNITION:

lf spark does not

occur look for:

.

Shorted ignition,kill

wlre

.

Two cosed

diodes in

ground

wire harness

.

Incorrect

a rmature

air

gap

FIECK

lGNnoN

{ENG NE RUNNING)I

ifengine

runs but misses

during

operation. a

quick

check to

determine if

ignition

is or is not

at fault

can be made by

installing

a spa*

tesler

(Generac

p,t\l

OC5969)

between the

spark

plug

lead

and each

spark

plug,

Figure t-6.

A spark mks

will be

rcadily

apparent

when the

engine is running. tf spark

i5

good

but

engine

misses, check

for a fouled

spark

plL'lg.

CHECK ]GNITION

(FOULED

PLUG OR OTHER

CAUSES):

To

check for a fouled spark

plug

or a nonjunctioning

cylin-

der. attach

the

lpark

tener

(Generac

P/N

OC5969)between

the

spark

plug

lead

and each spark

plug.

Stad and run

engine at

top no lo.d

speed. Now

ground

one spark

plug,

Fig! re t

-7.

The

engineshould

continue to run on the

other cylinder Repeatthis

test with the other

cylnder lf the engine

will not continue

to

run when making

thistest, the

cylinder that ls NOT

grounded

is not functioning

and/orthe

spark

plug

is fouled.

Installa new

spa*

plug

before

prcceeding.

f miss

cont n!es,

problem

may

be carburetion

orcompression. See

Check Calburction,

Check

Compression.

Also see Cy inder

BalanceTest.

Figvre

1-7. Checking

fot Fouled

plugs

CYL NDER EAIANCE TEST

lf the

enqine is hard stadinq,

runs rough,

misses or tacks

power, pertorm

a cylinder

balance test

to determirre

wnerner

boih

cylirdes are ope.ai 19

rc trerr fL lporenlrat.

Tools Requircdi

1. Two

gnition

Teste6

(Cenerac

P/N

OC5969)

Attach

an i9nition

tester betwe€n

the spark

plug

lead

and

each

spark

plug,

Fiqure

1'6.

Stadand run

engine runnln9

attop no load

speed and note

spark at ign

lion teste6. lf the

spa.k is equat

at both

jgniUon

testers,

the

problem

is not igniton

related.

A spark miss

will

be readily apparent. Now

note RPM

of engine. Ground

out one

cylinder by

contacting ignition

tester and a

good grcund

on

engrne, Figufel

8. Note RPM loss.

Then

ground

out the

other

spark

p

ug and note ihe RPNI

loss. lf the difference between

the two cylind€rs does not

exceed 75 RPNI, the amount

ofwork

the two

qlinde|s

are doing should be considered

equal.

figwe

1-6. Running

Check

J'

I

I

I

SECTION 1: GENERAL INFORMATION

I

lfthe RPw

loss isgrcaterthan 75 RPIV this

indicates that the

grcunded

cylinder

with the least RPM loss is the

weakest ot

the two cylinders.

Look to th.t

qlinderfora problem.

Example:

Engine RPM

-

Both cylinders = 3400 RPM

Engine RPM - #1 Cylindet Grcunded

=

3300 RPM

Engine

RPIV - *2 Cylinder Grounded

=

3100 RPM

Conclusion:#1

cyllnder is weakest of the two cylinders.

EXA[4PLE:

cyl. #1

cyl. #2 Diff.

Eng. +l

165 PSI

160 Psl 5 Psl

Eng.42 175

PSI 155 PSI 20 Psl

lf

compression

is

poor,

look for:

.

lnsufficient

valve clearance

.

Loose cyllnder

head bolts

.

Blown

head

gasket

.

Bumed va

ve5, valve seats and/or

loose

valve seats

.

warped

cylinder

head

.

warped

valve stems

.

Worn bofe and/or

rings

.

BDken

conneding

rods

CYLINDER

LEAKDOWN

TESI

A cylinder

leakdown tener

may be used to test the sealing

capability

of the compression

components of each cllinderand

quickly

identit the

prcblem

cornponent.

THINGS WHIC]]

AFFEEI-EO]ILIILNDIB!

l. Carburetion

2. Crankcase

vacuum

3.

lgnition timing

a.

A

partially

sheared

fl)4rvheelkey willeffect

ignition iimlng

and engine

Peaformance.

TH]NGS

WHIC H AFFECT

ONE CYL NDE R:

1. Spark

plug

a.

a fouled 5park

plug

may indicate that carburetor

is out

of adjustment.

2. Leak in spark

plug

wire

3. Head

gasket

4. lntake

manifod

a. A leak ateiiherend

ofthe

intake maoifold wlllonly affecl

one cylinder,

not both.

5.

Valves

6. RLngs

8. Cylinder
NOTE: A twin cylindet

engine

wi runwe ononecylin-

der as long as the

power

rcquircd

for the appli.ation does

not exceed the

powet

produced

by the one cylinder

Figwe |

-8.

Cylindet Salan.e Test

The cy

inder balance |en willa so detect a

qlinderthat

is not

functloning.

When

grcunding

out one cylinder thete

wil be

no

RPIV loss. When the other

qlinder

ls

grounded

out the

enqine

willsiop-

The fuel

prcssurc

can be checked using a

pressure

tester

kit

(Generac

P/N OC7977).

This kt comes with an lntormatve

'How

To' video.

CHECK COIVPRES5 ON:

lt

has

be€n

determlnedthrolghtestinq that a simple.nd

accu

rate indication of comprcssion

can be made as

fo lows:

Remove both spark

plugs

and nsert a compresslon

gaugeinto

either cylinder

(one

cylinder at a tirne).

Turn

efglne

over wilh

engine starter

until there is no further ncrease

in

pressure.

Record this reading.

Rep€ai

pfocedure

on olher cylirder

and

rccord

that reading.

The d Ifefence beiween both cy inde6

shouldnoiexceed25%.

Morcthan25% indicates ossof com-

press

on

in

the.ylinder

wth lower

presslre.

see examp

e.

1-5

SECTION

1:

6ENERAL

INFORMATION

EQUIPMENT

AFFECTING

ENGINE

OPERATION

Frequently,

whatappearsto

bea

problemwith

engine

oper-

ation,

such as

hard starting,

vibration,

etc., may

be the fault

of the

equipment

powered

rather than

the engine

itself. Listed

aA

the most

common

effects of equipment

problems'

and wilat

to

look

forasthe most

common

cause.

HARD

STARTING

OR WILL

NOT STARI

1 . Loose

belt

-

a loose belt

like a

loose blade can cause

a back-

lash

effec-t,

which wllcounteract

engine cranking

effort

2.

starting

under

load - see

i{ the unit

is disengaged

when

engine

is started;or

ifengaged,

should not

have a heavy

starting

load-

3. Check

remote

control

assembly

for

proper

adjustment-

4. Check

interlock

system

for shorted

wires, loose or corrcded

connections,

or

defective modules

or switches

ENG

INI WON'T

STOP:

1. Check

equipment

ignition stop

swjtch.

2. Check

for loose or

disconnected

equipment stop

swtcn

3-

check

ground

wire harness

on engrne.

a.

See Section

2 for test

Procedure,

V]BRATION:

1 .

Unit load out

of balance

-

remove and

balance.

2. Mounting

bolts loose

-

ughten.

r0wEe!05t

1 .

Bind or drag in unit-

if

possible,

disengage

engine

and oper-

ate unit

manuallyto feelforany

binding action

2. Unit load

ha5 excess dtag-

xol5E

1 . Engine coupling or

pulley

-

an oversize

or

worn couphng

can result in knocking,

usually under

acceleration.

Check

for fit or tightness.

2. Equipment

needs lub cation.

SECTION 2:

IGNITION

SECTION CONTENTS

PAGE

sPEClFlCATIONS..................

-..... --------------....-....

2-1

GENERAL

lNFORMAT|ON..... ...........................................

2-1

ARMATURES

Armatur€Testing................-.....................----..-.........2l

Removing

Amatures ........................-.......................

2_1

lnstall

Armatures -................ .....................................-.

2-1

Adjusi Armaturc Air Gap ..........................................

2-2

FL\1/VHEEL

Remove Flywheel ..-...................................-...............2_2

lnspect Flylvheel

Key and Keylv ays ...........-................

2"2

lnstallFlylvhee1..........................................................2_3

ENGTNE

WtRTNG HARNESS .....................-......................

2-3

Tesling Grcund Wircs............................................-...

2-3

Engine wirlng Harness Diagram

................................

2-4

Diode Failurc Diagnosis

...-.--.....................................

2-4

SPECIFICATIONS

FOR

GW-990/760

0HVt V-TW|N ENGINE

MODEL 5ERLE5 ................................................Gry-990t60

ARMATURE AIR GAP.....................................008',

TO .012'

(.20TO.30

MM)

FLYWHEEL NUI TORQUE

n: 185..........--......................

..

.. - - .......150

FL\1/VHEEL NUT TORQUE

NM............__.......................................-......................203.0

See Section

1 For Spatk PIug MainFnan.e

And Spe<ifi<ations

GENERAL INFORMATION

Generac

GTV-990,60 OHVIV-Twin

engines use a

magneto

ignltionr an

ignition amalure with a

seli-contalned transistor

module

(no

moving

paats).

Two magneto

ignition arrnatures

are used, with a flyljvheel

containing a

permanent

magnet.

NOTE:

fhe magneto ignition

synem rcquires a minimum

of 350

RPM to

ptoduce

a consistent

spa*.

ARMATURES

ARMATURE TESTING:

The condition

of lhe ignition armatures

can be accu€tely

diag'

nosed using

an ignition testet,

(Generac

P/N 0C5969) as

desc bed in

'Trcubleshoot

n9' in Section

1.

REMOV NG

ARMATURES:

1.

Remove spark

plug

leads.

2.

Remove intake manifod

and covel

intake

pofts.

3. Remove rotating

screen

and blower housing.

4. Remove

armature screws and lift off armature(s),

Figure 2-1.

a. Disconnect

stop swltch

wires

at armatures.

Note:The

flwheel does

not need to be rcmoved to ser-

vice ignition

except

to check the flwheel ket.

INSTATL

ARMATURES:

1- Turn

fylvheelso magnet

is away frcm amatur€.

2. Install

ground

wire onto tab terminalon armature.

Note:

Make sure wires

are routed over afinature mount-

ing

posB

and away

lrcm flwheel.

figute

2-2. Ins|.jrlling Anaturc

3.

Assembe armature

to engine,

Figurc 2-2.

a.

Mounting holes in armature

are slotted, Push armature

away from

fly\,vheel as far as

possible

and tighten one sc€w

to hold afmaturc

in

place.

Figurc

2-1. Renoving Amature

2-1

SECTION

2: IGNITION

4. Repeatfor

second

armature.

5. Adjust

armature air

gap.

ADIUST

ARMATUREAR GAP:

1.

Rotate fl!

rheel until magnet is underamatur€ laminalions.

2. Place thickness

9au9e,

.008 "

-.012

"

(0.20-.30

mm)

between

magnet

and armature

laminaiions, Fgurc 2-3

3.

Loosen

mounting screw so

magnet

will

pull

armature down

against thickness

gauge.

a.

Torque scrcws to

12.2 Nm

(9

Jt. lbs.).

4, Rotate

flylvheel to remove thlckness

gauge,

5. Repeatfor

second armatule-

Note:

Route amature

grcund

wire

over breather tube

and

away from the

flwheel.

Figurc 2-4, Remouing FIWheel Nut

Caution: Flywheel

pulle.bolts

may damage lighting

coilif turned

in

too

{ar.

cautionr Do NoT strike llywheel

with a hard objed
or a m€tal tool as this may Guse flywheelto shat­ter in operation. Always use approved flyl/vheel

Figure 2"5. Renoving Fl@heel

INSPECT FLYIVHEEL KEY KEWVAYS. FLYIVHEELAND
CRANKSHAFT:

Check

flywheel key for

damage. Check

fly\,vheel{or

cracks

or keluay danrage. Also check crankshaft

keylvays and

taper

for damage, Figure 2-6. Repace crankshaft,

if damaged.

A
A

FLYWHEEL

RE[,4OVE

FLY]/VHEEL:

1. Remove

fllavheelnut and washer, Figure 2-4.

2. Remove

fan retainer and fan.

4. Reinstall

flywheel nut. Turn nut down flush with top of

mrea05.

5. Install fllu/heeT

puller

6. Tighten

puller

screws equaly untll fly\,vheel loosens.

Figure

2,5.

Figurc 2-3, Adjusting

ai

Gap

2-2

SECTION 2: IGNITION

Figue 2-6, Che.k

Hwheel And eankshaft

INSTALL FL\ryVHEEL:

Note: CLEAN flwheel

and

(ankshaft

taper removing

all

oil, dirt or

gtease.

1.

Insertflylvheel key into crankshaft.

2. Align

keyways and assernble flylvheel to crankshaft.

3. Installwasher and

flylvheel nut.

a. Toque fly,vl/heelnut to

203.0 Nm

(150

ft.lbs.),

Fiqure 2-7.

4. as5emblefan and retainerto

flywheel, Figure 2 8.

a.Torque screws to

2l.7 Nm

(192ln.

lbs.).

Figure 2-7,

Totquing Flwheel Nut

Figurc 2-S.lnsta ing Flywheel And

Fan

ENGINE KILL WIRES

The

engine

kill wires conslst of a

grcund

wire with a diodefor

each armatureand

a separate wire for the carbu retor solenoLd.

The engine killwires are connected

to the wirlng harness

pro-

vided by the equipment manulacturer

See engine

wire diagram,

Page 6-3.

TESTiNG GROUND WIRES:

Use a

Digital Multimeter

(Figure

2-9) to test the

ground

wires.

The iollowing test w

llbe made with the meter in the Diode Ten

In the Diode

Test

position,

the meter will display the foftvard

voltage drop acrcssthe

diode(s). lf the voltage drop is less than

0.7

volts, the meter will ' Beep' once as

well

as display the

volt-

age drop. A continuous

tone indicates continuity(shoned diode)

An incomplete circuit

(open

diode) will be displayed as

'OL. '

2.3

Figurc 10. Digital Multinetel

SECTION 2: IGNITION

'L

tnsed

RED test lead

into

yo+

receptacle

in meter.

2. Insen

ELqCK

ten lead

intothe.,COM.

re.eptacle

In

meter

3.

Rotate

selector

to

>i n t (Diode

Test) posttio,r

4. hsert

RED test

lead

clip into

connector

.

A'

(Fiqure

2_ I

0).

Leave

attached

for

femainder

of test.

5. Touch BLACK

ten lead

probe

to terminat

,8.,,

a.lf meter

'Beeps'

once,

diode

is OK.

b.lf meter

makes:

continuoLrs

tone,

diode is

defective

Ghorted).

Replrce

ground

harness.

c. lf meter

displays

'OL,'

diod€

is defective (open).

Replace

ground

harness.

6. Now

repeat

test for

terminal

,

C, , Results

must

be

the same.

See

"Diode

Failwe

Diagnosis-

betow

SPARK

PLUG

SPARK

PLUG

DIODE

figute

2-11.

lgnition

Whing

Hamess

DIODE

FAITURE

DIAGNOSIS

IGNITION

KILLWIRE

ENGINE
GBOUND
HARNESS

POSITIVE

Ii4ETEB

TEST

LEAD

NEGATIVE

I\4ETER

Figurc

2-10. Testing

Grcund

Whe

GROUND
WIRE
HARNESS

SWITCH

ON

TURNED

OFF

CAUSE

Engine

Runs

On I

Cy/jnder

shuts

off oK

I

Closed

Diode

Engine

Runs

(Both

Cylinders)

OnIy

One

Cylinder

shuts

Off

I

Open Diode

(No

Spark)

2 Closed

Diodes

Engine

RLins

(Both

Cylinders)

Engine

Won t

Shut

Off

2 Open

Drodes

2-4