Generac Power Systems GTH760, GTH990, GTV990, GTV1000, GTH1000 Service Manual

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ENGINE

SERVICE

MANUAL

OHVI® V-Twin Engine

MODELS:

GTH760/990/1000

GTV760/990/1000

AIR-COOLED ENGINES

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.

RULES FOR SAFE OPERATION

4-CYCLE ENGINE THEORY

TABLE OF CONTENTS

SECTION 1: GENERAL INFORMATION

SECTION 2: IGNITION

SECTION 3: CARBURETION AND FUEL SYSTEM

SECTION 4: GOVERNOR CONTROLS AND GOVERNOR

SECTION 5: CYLINDER HEAD AND VALVES

SECTION 6: ELECTRIC STARTER

SECTION 7: ALTERNATORS

SECTION 8: LUBRICATION SYSTEM

SECTION 9: ENGINE DISASSEMBLY

SECTION 10: CYLINDER AND CRANKCASE COVER

SECTION 11: CRANKSHAFT AND CAMSHAFT

SECTION 12: PISTON, RINGS AND CONNECTING ROD INSPECTION AND ASSEMBLY

SECTION 13: ENGINE ASSEMBLY

SECTION 14: SPECIFICATIONS

Generac Power Systems does not approve or authorize the use of these engines on All Terrain Vehicles (ATV’s), go-carts, motorbikes, aircraft products, personal watercraft, or vehicles intended for use in competitive events. The use of this product in any other than it’s intended application will void the warranty! Use of these engines in such applications could result in property damage, serious injury (including paralysis), or even death.

ATTENTION!

RULES FOR SAFE OPERATION

If any portion of this manual is not understood, contact the nearest Dealer for starting, operating and servicing procedures.

Throughout this publication, and on tags and decals affixed to the equipment, DANGER, WARNING, CAUTION and NOTE blocks are used to alert personnel to special instructions about a particular operation that may be hazardous if performed incorrectly or carelessly. Observe them carefully. Their definitions are as follows:

INDICATES A HAZARDOUS SITUATION OR ACTION WHICH, IF NOT

AVOIDED, WILL RESULT IN DEATH OR SERIOUS INJURY.

Indicates a hazardous situation or action which, if not

avoided, could result in death or serious injury.

Indicates a hazardous situation or action which, if not

avoided, could result in minor or moderate injury.

NOTE:

Notes contain additional information important to a procedure and will be found within the regular text body of this manual.

These safety warnings cannot eliminate the hazards that they indicate. Common sense and strict compliance with the special instructions while performing the action or service are essential to preventing accidents.

Four commonly used safety symbols accompany the DANGER, WARNING and CAUTION blocks. The type of information each indicates is as follows:

This symbol points out important safety information that, if



not followed, could endanger personal safety and/or property of others.

This symbol points out potential explosion hazard.

This symbol points out potential fire hazard.

This symbol points out potential electrical shock hazard.

The operator is responsible for proper and safe use of the equipment. The manufacturer strongly recommends that the operator read this Owner’s Manual and thoroughly understand all instructions before using this equipment. The manufacturer also strongly recommends instructing other users to properly start and operate the unit. This prepares them if they need to operate the equipment in an emergency.

RULES FOR SAFE OPERATION

Study these RULES FOR SAFE OPERATION carefully before operating or servicing this equipment. Become familiar with the OWNER’S MANUAL and with the engine. The engine can operate safely, efficiently and reliably only if it is properly operated and maintained. Many accidents are caused by failing to follow simple and fundamental rules or precautions.

The manufacturer cannot anticipate every possible circumstance that might involve a hazard. The warnings in this manual and on tags and decals affixed to the equipment, are therefore, not all-inclusive. If using a procedure, work method or operating technique the manufacturer does not specifically recommend, ensure that it is safe for others. Also make sure the procedure, work method or operating technique utilized does not render the engine to be unsafe.

DO NOT tamper with the engine governed speed.



High operating speeds are dangerous and increase the risk of personal injury or damage to the equipment. Operating at low speeds with heavy load may shorten the engine’s life.

BEFORE OPERATING

•Gasoline is highly FLAMMABLE and its vapors are EXPLOSIVE. Do not permit smoking, open flames, sparks or heat in the area while handling gasoline. Avoid spilling gasoline on a hot engine. Comply with all of the laws regulating storage and handling of gasoline.

•Store gasoline and other fuels only in containers designed and approved for the storage of such materials.

•Pressure can build up in the fuel tank. Loosen the fuel cap slowly to relieve any pressure in the tank.

•Add gasoline and other fuels in a clean, well-ventilated area. Wipe up any spilled gasoline immediately. If gasoline has been spilled, let it dry completely before starting the engine.

•Do not overfill the fuel tank. Always allow room for fuel expansion. If the tank is overfilled, the fuel can overflow onto a hot engine and cause a FIRE or an EXPLOSION.

•Thoroughly inspect the engine for loose or damaged parts before each use. Do not use the engine until adjustments or repairs are made.

•Check the oil level in the engine before each use.

•Inspect the engine periodically. Repair or replace all 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 modify the engine fuel system in any way that might affect safety or compliance with applicable codes and standards.

WHILE OPERATING

RULES FOR SAFE OPERATION

•This engine was designed and manufactured for specific applications. Do not attempt to modify the equipment or use it for any application for which it was not designed.

• Engine exhaust gases contain DEADLY carbon monoxide gas. This dangerous gas, if breathed in sufficient concentrations, can cause unconsciousness or even death. Operate this equipment only in the open air where adequate ventilation is available.

•Do not insert any object through the cooling slots of the engine. This could damage the equipment or injure personnel.

• Do not operate the engine faster than the speed necessary to operate the equipment. Do not run the engine at high speed when not operating the equipment.

•This engine requires an adequate flow of cooling air for its continued proper operation. Never operate the equipment inside any room or enclosure where the free flow of cooling air into and out of the equipment might be obstructed. Without sufficient cooling air flow, the engine quickly overheats, damaging the engine or nearby property.

•Do not smoke around the engine. Wipe up any fuel or oil spills immediately. Never leave oily or fuel soaked rags around the engine. Keep the area around the engine clean and free of debris.

•Keep hands, feet, clothing, etc., away from moving parts of this engine.

•Never operate the engine (a) in the rain; (b) in any enclosed compartment; (c) if the engine speed changes; (d) if the engine sparks; (e) if flame or smoke is observed while the engine is running.

•Never work on this engine or handle any electrical device while standing in water, while barefoot, or while hands or feet are wet. DANGEROUS ELECTRIC SHOCK will result.

•Allow muffler, engine cylinder and fins to cool before touching.

•Remove accumulated combustibles from muffler area and cylinder

area.

•Install and maintain in working order a spark arrester before using equipment on forest covered, grass covered, brush covered unimproved land. The state of California requires this (Section 4442 of the California Public Resources Code). Other states may have similar laws. Federal laws apply on federal land.

SERVICE INFORMATION

Service on this engine within and after the warranty period can be performed by any authorized service dealer. Service technicians are factory trained and capable of handling all service needs.

When contacting an authorized service dealer about parts and service, always supply the com- plete model number and serial number of your unit as given on its data plate decal. See the illustration below for the location of the decal.

The warranty for this engine is included in the owner’s manual.

CALIFORNIA PROPOSITION 65 WARNING

Engine exhaust and some of its constituents are known

to the State of California to cause cancer, birth defects

and other reproductive harm.

CALIFORNIA PROPOSITION 65 WARNING

This product contains or emits chemicals known to the

State of California to cause cancer, birth defects and

other reproductive harm.

Running engines produce heat. Engine parts, especially muffler, become extremely hot. Severe thermal burns can occur on contact. Combustible debris, such as leaves, grass, brush, etc. can catch

fire.

4-CYCLE ENGINE THEORY

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.

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.

(C)

IGNITION AND POWER

(B)

COMPRESSION

As the piston reaches bottom dead center (BDC), both the intake and exhaust valves are closed. As the piston moves upward toward TDC, the fuel-air mixture becomes compressed. Just before the piston reaches TDC, ignition occurs.

(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.

SECTION 1: GENERAL INFORMATION

MAINTENANCE SCHEDULE

Every 8

Hours

or Daily

Every 50 Hours or

Yearly

Every

100

Hours or

Yearly

Check Oil Level •

Change Oil Note 1 Note 1

Change Oil Filter Note 1 Note 1

Service Air Filter Note 2

Fuel Filter •

Replace or Clean Spark Plug

Clean Spark Arrestor Screen

Check Valve Clearance

Note 3 Note 3

•

Note 1: Change oil and filter after first eight (8) hours of operation and then every 100 hours thereafter. Change sooner when operating under a heavy load or in a dusty or dirty environment or in high ambient temperatures.

Note 2: Service more often when operating in dirty or dusty conditions.

Note 3: Check valve clearance and adjust (if necessary) after first 50 hours of operation and every 100 hours thereafter.

Every

500

Hours

or Yearly

LUBRICATION:

Oil has four purposes. It cools, cleans, seals and lubricates. During normal operation, small particles of metal from the cylinder walls, pistons, bearings and combustion deposits will gradually contaminate the oil. Dust particles from the air also contaminate the oil forming an abrasive mixture which can cause wear to all of the internal moving parts of the engine, if the oil is not changed regularly. Fresh oil also assists in cooling. Old oil gradually becomes thick and loses its cooling ability as well as its lubricating qualities.

RECOMMENDED OIL TYPE:

Using the proper type and weight of oil in the crankcase is extremely important. Check the oil before each use and change the oil regularly (see Figures 1-1 through 1-5). Failure to use the correct oil, or using dirty oil, can cause premature engine wear and failure.

Use only high quality detergent oil rated with an API service classification SN or higher. Do NOT use oil designated "for diesel engines only" (example: CD).

The recommended oil weights include the following:

•During summer months: SAE 30. An acceptable substitute is SAE 10W-30. After first oil change, synthetic oil is acceptable.

•During winter months: SAE 5W-30 or synthetic 5W-30. DO NOT USE SAE 10W-40.

After first oil change, synthetic oil is acceptable.

FUEL AND OIL RECOMMENDATIONS

GASOLINE:

We recommend the use of clean, fresh lead-free gasoline. A minimum of 85 octane is recommended. The use of lead-free gasoline results in fewer combustion deposits and longer valve life.

Note: Using a fuel additive such as STA-BIL® fuel stabilizer, or an equivalent, will prevent gum deposits from forming in the engine’s fuel system.

Note: Some fuels, called oxygenated or reformulated gasolines, are gasolines blended with alcohols, ethers or ethanol. Excessive amounts of these blends can damage the fuel system or cause performance problems. Do not use gasoline which contains Methanol. Use gasoline with the lowest percentage of alcohol, ether or ethanol—10% or less.

It is also recommended that gasoline be purchased in small quantities, not more than a 30 day supply. FRESH gasoline minimizes gum deposits, and also will ensure fuel volatility tailored for the season in which the engine will be operated.

CHANGE OIL:

See "Section 14: Specifications" for crankcase oil capacities. Use no special additives. Make sure that the unit is level when filling with oil. DO NOT OVERFILL.

IMPORTANT: DO NOT OVERFILL. Check and maintain oil level regularly. Change oil and filter after first eight (8) hours of operation.

Thereafter, change oil and filter every 100 hours of operation. Change oil more often if engine is operated in dirty or dusty conditions or if engine is operated under heavy loads or in high ambient air temperatures.

1-1

SECTION 1: GENERAL INFORMATION

FILL / CHECK

Figure 1-1. Oil Fill/Check Vertical Engine

CHANGE OIL FILTER:

Replace oil filter every 100 hours. Before installing new filter, lightly oil filter gasket with fresh clean engine oil. Screw filter on by hand until gasket contacts filter adapter. Tighten 3/4 to one full turn far ther (Figure 1-5).

Start and run engine at idle for 30 seconds and stop engine. Recheck oil level and add if required. Restart engine and check for oil leaks.

OIL CHECK

Figure 1-2. Oil Check Horizontal Engine

OIL FILL

Figure 1-3. Oil Fill Horizontal Engine

Remove oil drain plug and drain oil while engine is still warm, Figure 1-4. Change oil filter (Figure 1-5) and replace drain plug.

Remove dipstick or fill cap and fill slowly with new oil of proper service classification and viscosity grade. Fill to full mark on dipstick. When checking oil level, dipstick must be inserted all the way in for accurate readings.

DRAIN

Figure 1-4. Oil Drain

FILTER

Figure 1-5. Oil Filter

CLEANING INTAKE SCREEN:

Grass particles, chaff or dirt can clog the air cooling system, especially after prolonged service in cutting dry grass or when operating in extremely dusty or dirty conditions. Continued operation with a clogged cooling system can cause severe overheating and possible engine damage. Figure 1-6 shows the areas to be cleaned. This should be a regular maintenance operation, or clean intake screen and oil cooler fins after each use.

1-2

INTAKE

SCREEN

SECTION 1: GENERAL INFORMATION

The air cleaner on every engine brought in for a check up or repair should be examined and serviced. If the air cleaner shows signs of neglect, show it to the customer before cleaning. Instruct the customer on proper care, to assure long engine life.

OIL

COOLER

FINS

Figure 1-6. Clean Intake Screen & Oil Cooler Fins

REPLACE SPARK PLUGS:

Replace spark plugs every 100 hours of operation or every season, whichever occurs first. Replace spark plugs if electrodes are burned away, or the porcelain is cracked. Set spark plug gap at 1.1 mm (0.043") for all models. Torque spark plugs to 19.0 Nm (168 in. lbs.).

SET PLUG GAP AT 1.1mm

(0.043 inch)

Note: Replace air cleaner gaskets and mounting gaskets that are worn or damaged, to prevent dirt and dust from entering engine due to improper sealing. Replace bent air cleaner mounting bracket if necessary.

SERVICE CANISTER AIR CLEANERS:

Clean the air filter element(s) with compressed air every 50 hours or every season, whichever occurs first. Replace the air filter element(s) every 500 hours or if damaged (see Figure 1-8).

Figure 1-8. Canister Air Cleaner Components

Figure 1-7. Setting Spark Plug Gap

Note: For proper spark plug replacement, refer to the owner’s manual for the specific product.

AIR CLEANER MAINTENANCE:

WARNING: NEVER OPERATE ENGINE WITH AIR CLEANER

ASSEMBLY OR AIR CLEANER CARTRIDGE REMOVED. FIRE

MAY RESULT.

A properly serviced air cleaner protects internal par ts of the engine from dirt and dust particles in the air. If air cleaner instructions are not carefully followed, dirt and dust which should be collected in the cleaner will be drawn into the engine. These particles are highly abrasive and will cause the piston rings and cylinder bore to wear quickly. As the rings and cylinder bore become worn, these abrasive particles enter the crankcase and contaminate the oil, forming an abrasive mixture which will cause wear on all of the internal moving parts.

SERVICE DUAL ELEMENT AIR CLEANERS:

Remove and service foam pre-cleaner every 25 hours or every season, whichever occurs first. Service cartridge every 50 hours or every season, whichever occurs first (see Figure 1-9).

COVER

AIR FILTER

ELEMENT

FOAM PRE-CLEANER

Figure 1-9. Dual Element Air Cleaner Components

1-3

SECTION 1: GENERAL INFORMATION

Note: The air cleaner assemblies on some equipment may have been supplied by the equipment manufacturer. See the equipment manufacturer’s owner’s manual for service information specific to that product.

TROUBLESHOOTING

Most complaints concerning engine operation can be classified as one or a combination of the following:

1. Will not start

2. Hard starting

3. Lack of power

4. Runs rough

5. Vibration

6. Overheating

7. High oil consumption

Note: What appears to be an engine malfunction may be a fault of the powered equipment rather than the engine. If equipment is suspect, see equipment affecting engine operation.

SYSTEMATIC CHECK

If the engine will not start and the cause of malfunction is not readily apparent, perform a systematic check in the following order:

CHECK IGNITION:

If spark does not occur look for:

•Shorted ignition/ground wire (see Page 2-1)

•Two closed diodes in ground wire harness (see Page 2-1)

•Incorrect ignition coil air gap (see Page 2-3)

•Ignition coil failure

•Weak flywheel magnet

CHECK IGNITION (ENGINE RUNNING):

If engine runs but misses during operation, a quick check to determine if ignition is or is not at fault can be made by installing a spark tester (Generac P/N 0C5969) between the spark plug lead and each spark plug, Figure 1-10. A spark miss will be readily apparent when the engine is running. If spark is good but engine misses, check for a fouled spark plug.

SPARK PLUG LEAD

TESTER

1. Fuel

2. Ignition

3. Compression

This check-up, performed in a systematic manner, can usually be done in a matter of minutes. It is the quickest and surest method of determining the cause of failure. The basic checkup procedure is the same for all engine models, while any variation, by model, will be shown under the subject heading.

CHECK FUEL:

The fuel pressure on LP and NG generator engines can be checked using a pressure test kit for LP and NG systems.

For gasoline engines, check the following:

1. Are the tanks full?

2. Is the fuel stale?

3. Is the tank vent open?

4. Is the fuel shutoff valve open?

5. Is the fuel pump working?

6. Is the fuel solenoid working?

SPARK PLUG

Figure 1-10. Running Check

CHECK IGNITION (FOULED PLUG OR OTHER CAUSES):

To check for a fouled spark plug or a non-functioning cylinder, attach the spark tester (Generac P/N 0C5969) between the spark plug lead and each spark plug. Start and run engine at top no load speed. Now ground one spark plug, Figure 1-11. The engine should continue to run on the other cylinder. Repeat this test with the other cylinder. If the engine will not continue to run when making this test, the cylinder that is NOT grounded is not functioning and/or the spark plug is fouled. Install a new spark plug before proceeding. If miss continues, problem may be carburetion or compression. See Check Fuel, Check Compression, and Cylinder Balance Test.

1-4

Figure 1-11. Checking For Fouled Plugs

CYLINDER BALANCE TEST:

If the engine is hard starting, runs rough, misses or lacks power, perform a cylinder balance test to determine whether both cylinders are operating to their full potential.

Tools Required:

SECTION 1: GENERAL INFORMATION

CHECK COMPRESSION:

It has been determined through testing that a simple and accurate indication of compression can be made as follows:

Remove both spark plugs and insert a compression gauge into either cylinder (one cylinder at a time). Open the throttle to Wide Open Throttle (WOT) position. Turn engine over with engine starter until there is no further increase in pressure. Record this reading. Repeat procedure on other cylinder and record that reading. The difference between both cylinders should not exceed 25%. More than 25% indicates loss of compression in the cylinder with lower pressure. See example.

EXAMPLE: Cyl. #1 Cyl. #2 Diff. Eng. #1 165 PSI 160 PSI 5 PSI Eng. #2 175 PSI 155 PSI 20 PSI

If compression is poor, look for:

Insufficientvalveclearance • Warpedcylinderhead

•

•Loosecylinderheadbolts • Warpedvalvestems

•Blownheadgasket • Wornboreand/orrings

• Burned valves, valve seats

and/or loose valve seats

1. Two Ignition Testers (Generac P/N 0C5969)

Attach an ignition tester between the spark plug lead and each spark plug, Figure 1-10.

Start and run engine at top no load speed and note spark at ignition testers. If the spark is equal at both ignition testers, the problem is not ignition related. A spark miss will be readily apparent. Now note RPM of engine. Ground out one cylinder by contacting ignition tester and a good ground on engine, Figure 1-11. Note RPM loss. Then ground out the other spark plug and note the RPM loss. If the difference between the two cylinders does not exceed 75 RPM, the amount of work the two cylinders are doing should be considered equal.

If the RPM loss is greater than 75 RPM this indicates that the grounded cylinder with the least RPM loss is the weakest of the two cylinders. Look to that cylinder for a problem.

Example:

Engine RPM - Both Cylinders = 3400 RPM

Engine RPM - #1 Cylinder Grounded = 3300 RPM

Engine RPM - #2 Cylinder Grounded = 3100 RPM

Conclusion: #1 cylinder is weakest of the two cylinders.

The cylinder balance test will also detect a cylinder that is not functioning. When grounding out one cylinder there will be no RPM loss. When the other cylinder is grounded out the engine will stop.

Model Normal Compression

GTH/GTV-760 130-160 psi

GTH/GTV-990/1000 160-190 psi

CYLINDER LEAKDOWN TEST

A cylinder leak down test will indicate the condition of the cylinder. It will assist in troubleshooting the engine’s condition such as leaking valves or rings.

On some testers there will be two gauges, one will be the incoming air pressure and the other will measure the percent of cylinder leakage (see Figure 1-12).

CYLINDER LEAK DOWN TEST PROCEDURE:

1. Piston must be at TDC of the compression stroke.

2. Install the tester into the spark plug hole.

3. The crankshaft/flywheel must be safely locked down to prevent turning.

4. Pressurize the cylinder to 90 psi.

5. Observe the leakage of the cylinder and where the air is coming from.

NOTE: If leaking into intake or exhaust port, check lash, valve face, and seat condition.

1-5

SECTION 1: GENERAL INFORMATION

INLET GUAGE

COMPRESSED AIR IN

AIR PRESSURE REGULATOR

RED RANGE INDICATES UNACCEPTABLE LEAKAGE

OUTLET GUAGE

PRESSURE SET POINT

OUTLET GUAGE PRESSURE

REGULATOR ADJUSTMENT KNOB

NEEDLE INDICATES MINIMAL AIR LEAKAGE

GREEN RANGE INDICATES ACCEPTABLE LEAKAGE

NOTE: A twin cylinder engine will run well on one cylinder as long as the power required for the application does not exceed the power produced by the one cylinder.

EQUIPMENT AFFECTING ENGINE OPERATION

Frequently, what appears to be a problem with engine operation, such as hard starting, vibration, etc., may be the fault of the equipment rather than the engine itself. Listed are the most common effects of equipment problems, and what to look for as the most common cause.

HARD STARTING OR WILL NOT START:

1. Loose belt - a loose belt like a loose blade can cause a backlash effect, which will counteract engine cranking effort.

2. Starting under load - see if the unit is disengaged when engine is started; or if engaged, should not have a heavy starting load.

Figure 1-12. Cylinder Leakdown Tester

RESULTS:

1. 0-10% Cylinder is good

2. 10-30% there may be a problem

3. 30-100% Cylinder requires repair

THINGS WHICH AFFECT BOTH CYLINDERS:

1. Carburetion

2. Crankcase vacuum

3. Ignition timing

a. A partially sheared flywheel key will effect ignition timing and

engine performance.

THINGS WHICH AFFECT ONE CYLINDER:

1. Spark plug

a. A fouled spark plug may indicate the carburetor is out of

adjustment.

2. Leak in spark plug wire

3. Head gasket

4. Intake manifold

a. A leak at either end of the intake manifold will only affect one

cylinder, not both.

5. Valves

3. Check remote control assembly for proper adjustment.

4. Check interlock system for shorted wires, loose or corroded connections, or defective modules or switches.

ENGINE WON'T STOP:

1. Check equipment ignition stop switch.

2. Check for loose or disconnected equipment stop switch wire.

3. Check ground wire harness on engine.

a. See Section 2 for test procedure.

VIBRATION:

1. Unit load out of balance (pulley, clutch or blades) - remove and replace.

2. Mounting bolts loose - tighten.

POWER LOSS:

1. Bind or drag in unit- if possible, disengage engine and operate unit manually to feel for any binding action.

2. Unit load has excess drag.

NOISE:

1. Engine coupling or pulley - an oversize or worn coupling can result in knocking, usually under acceleration. Check for fit or tightness.

2. Equipment needs lubrication.

6. Rings

7. Piston

8. Cylinder

1-6

SECTION 2: IGNITION

ENGINE GROUND HARNESS

POSITIVE METER

TEST LEAD

CYL #2

IGNITION

GROUND

WIRE STUD

CYL #1

NEGATIVE METER

TEST LEAD

GENERAL INFORMATION

Generac GTH/GTV-760/990 OHVI V-Twin engines use a magneto ignition: an ignition coil with a self-contained transistor module (no moving parts). Two magneto ignition coils are used, with a flywheel containing a permanent magnet.

NOTE: The magneto ignition system requires a minimum of 300 RPM to produce a consistent spark.

ENGINE WIRING HARNESS

The engine wiring harness consists of a ground wire with a diode for each ignition coil and a separate wire for the carburetor solenoid. The engine ground wires are connected to the wiring harness provided by the equipment manufacturer.

NOTE: Models built after 2007 will have the diodes built into the ignition coils or spark plug leads. Check the wire harness. If there are no diodes in the harness, perform test on the coil ground terminal.

See Figure 2-4.

TESTING GROUND WIRES:

Use a Digital Multimeter (Figure 2-1) to test the ground wires.

The following test will be made with the meter in the Diode Test position.

attached for remainder of test.

5. Touch BLACK test lead probe to terminal "B."

a. If meter "Beeps" once, diode is OK.

b. If meter makes a continuous tone, diode is defective (shorted).

Replace ground harness.

c. If meter displays "OL," diode is defective (open). Replace ground

harness.

6. Now repeat test for terminal "C." Results must be the same.

7. Replace wiring if defective.

8. If wiring tests good, proceed to IGNITION COILS section to replace defective coil.

Note: See “Diode Failure Diagnosis”, Figure 2-3.

In the Diode Test position, the meter will display the forward voltage drop across the diode(s). If the voltage drop is less than 0.7 volts, the meter will "Beep" once as well as display the voltage drop. A continuous tone indicates continuity (shorted diode) An incomplete circuit (open diode) will be displayed as "OL."

Figure 2-1. Digital Multimeter

1. Insert RED test lead into

2. Inser t BLACK test lead into the “COM” receptacle in meter.

receptacle in meter.

Figure 2-2. Testing Ground Wire

SWITCH ON TURNED OFF CAUSE

Engine Runs

Shuts Off OK 1 Closed Diode

On 1 Cylinder

Engine Runs

(Both Cylinders)

Won't Run

Only One

Cylinder

1 Open Diode

2 Closed Diodes

(No Spark)

Engine Runs

(Both Cylinders)

Engine Won't Shut

Off

2 Open Diodes

Figure 2-3. Diode Failure Diagnosis

WIRE HARNESS CHECK

3. Rotate selector to (Diode Test) position.

4. Insert RED test lead clip into connector "A" (Figure 2-2). Leave

IGNITION COIL TESTING:

If ignition does not have spark, disconnect ground wire from ignition

2-1

SECTION 2: IGNITION

DIODE (BUILT INTO COIL)

SPARK PLUG

GROUND WIRE HARNESS

DIODE (BUILT INTO COIL)

SPARK PLUG

Figure 2-4. Engine Wiring Harness

ground stud on engine and re-check. If ignition now has spark, check wire harness for pinched wires, broken insulation or bad diode (if equipped). If there is no spark, proceed to Removing Ignition Coil section.

REMOVING AND INSTALLING WIRE HARNESS:

1. Remove spark plug leads.

IGNITION GROUND WIRE

DIODE BUILT IN HARNESS ON OLDER MODELS

Note: The flywheel does not need to be removed to service ignition except to check the flywheel key.

2. Remove intake manifold and cover intake ports with a shop towel.

3. Remove rotating screen and blower housing.

4. Disconnect stop switch wire(s) at ignition coil(s).

5. Reverse order of above to install new wire harness.

REMOVING IGNITION COILS:

The condition of the ignition coils can be accurately diagnosed using a spark tester (Generac P/N 0C5969) as described in "TROUBLESHOOTING" Section 1.

1. Remove spark plug leads.

2. Remove intake manifold and cover intake ports with a shop towel.

3. Remove rotating screen and blower housing.

4. Disconnect ground wire(s) at ignition coil(s).

5. Remove ignition coil screws and remove ignition coil(s). See Figure 2-5.

Figure 2-5. Removing Ignition coil

INSTALL IGNITION COILS:

1. Turn flywheel so magnet is away from ignition coil.

2. Install ground wire onto tab terminal on ignition coil.

Note: Make sure wires are routed over ignition coil mounting posts and away from flywheel.

3. Assemble ignition coil to engine, Figure 2-6.

a. Mounting holes in ignition coil are slotted. Push ignition coil

away from flywheel as far as possible and tighten screws.

4. Repeat for second ignition coil.

5. See Adjust Ignition Coil Air Gap.

2-2

SECTION 2: IGNITION

FLYWHEEL

REMOVE FLYWHEEL:

1. Remove two screws that attach fan and fan retainer to flywheel.

2. Remove fan retainer and fan.

GROUND WIRE ROUTING

Figure 2-6. Installing Ignition coil

ADJUST IGNITION COIL AIR GAP:

1. Rotate flywheel until magnet is aligned with ignition coil laminations.

2. Place 0.20-.30 mm (.008"-.012") thickness, non-magnetic gauge between magnet and ignition coil laminations, Figure 2-7.

3. Loosen mounting screws so magnet will pull ignition coil against thickness gauge.

a. Torque screws to 4.75 Nm (40 in. lbs.).

0.20-0.30mm SHIM

SOCKET WRENCH

3. Loosen flywheel nut until it is flush with end of crankshaft threads (Figure 2-8.)

4. Install flywheel puller.

5. Tighten puller screws equally until flywheel loosens, Figure 2-9.

6. Remove puller, nut, washer and flywheel.

Figure 2-8. Removing Flywheel Nut

GROUND WIRE TERMINAL

Figure 2-7. Adjusting Air Gap

4. Rotate flywheel to remove thickness gauge.

5. Repeat for second ignition coil.

Note: Route ignition coil ground wire under breather tube and away from the flywheel (see Figure 2-9).

Caution: Flywheel puller bolts may damage lighting coil if turned

in too far.

Caution: DO NOT strike flywheel with a hard object or a metal

tool as this may cause flywheel to shatter in operation. Always use approved flywheel removal tools.

INSPECT FLYWHEEL KEY, KEYWAYS, FLYWHEEL AND CRANKSHAFT:

Check flywheel key for damage. Check flywheel for cracks or keyway damage. Also check crankshaft keyways and taper for damage, Figure 2-10. Replace crankshaft, if damaged.

2-3

SECTION 2: IGNITION

COIL WIRE ROUTED

UNDER BREATHER

FLYWHEEL

NUT

Figure 2-9. Removing Flywheel

INSPECT HERE

Figure 2-10. Check Flywheel And Crankshaft

INSTALL FLYWHEEL:

Note: CLEAN flywheel and crankshaft taper removing all oil, dirt or grease.

1. Insert flywheel key into crankshaft.

Figure 2-11. Torquing Flywheel Nut

Figure 2-12. Installing Flywheel Fan

3. Install washer and flywheel nut.

a. Torque flywheel nut to 204.0 Nm (150 ft. lbs.), Figure 2-11.

4. Assemble fan and retainer to flywheel, Figure 2-12.

a. Torque screws to 21.7 Nm (182 in. lbs.).

2. Align keyways and assemble flywheel to crankshaft.

2-4

SECTION 3: CARBURETION AND FUEL SYSTEM

CARBURETOR TYPES

All Generac gasoline powered OHVI V-Twin engines utilize a two-barrel type carburetor. Some LP engines use a single barrel carburetor.

CARBURETOR REMOVAL - VERTICAL SHAFT

1. Unclip choke link from bellcrank and remove link from carburetor.

2. Disconnect fuel-shutoff solenoid by unplugging the power wire.

3. Disconnect breather tube and EVAP hose if equipped.

4. Separate throttle link balljoint from carburetor by rotating the ball socket.

5. Disconnect the fuel line clamp and the fuel line.

SPEED CONTROL LEVER

SLOW

BREATHER

HIGH

CHOKE

LINK

6. Remove the four nuts holding the carburetor and plenum to the intake manifold (see Figure 3-6).

7. Remove the plenum, carburetor and gaskets from the manifold and discard the gaskets.

CARBURETOR REMOVAL – HORIZONTAL SHAFT

1. Remove air cleaner cover and air cleaner.

2. Unthread yellow plastic knob from Summer/Winter intake control (if equipped)

3. Remove dipstick tube hold down bolt and remove tube assembly (see Figure 3-3).

4. Remove the four nuts and one bolt that retains the air cleaner base, breather tube and EVAP hose if equipped; remove base (see Figure 3-3).

5. Remove fuel line clamp and fuel line from top of carburetor.

4 NUTS

BOLT

BELL CRANK

Figure 3-1. Vertical Shaft Carburetor

CLIP

DIPSTICK TUBE &

HOLD DOWN

Figure 3-3. Horizontal Shaft Carburetor

THROTTLE LINK

Figure 3-2. Vertical Shaft Carburetor

Figure 3-4. Horizontal Shaft Carburetor

3-1

SECTION 3: CARBURETION AND FUEL SYSTEM

CHOKE LINK

Figure 3-5.

6. Remove choke link (Figure 3-5), throttle link (Figure 3-4) and fuel shut-off solenoid wire from carburetor.

7. Slide carburetor off mounting studs.

CARBURETOR CLEANING

For cleaning purposes, the carburetor's float bowl may be removed. It is recommended that all jetting be left in place while cleaning the carburetor. Be sure to use a cleaner that won't damage rubber, neoprene, or plastic parts.

Note: The left and right main jets are different sizes.

If the fuel-shutoff solenoid is suspected of being faulty, it is replaceable by simply unthreading it from the float bowl, and installing a new one in its place. It can be checked by applying 12 volts to it. If you hear it click, it is most likely working properly. If there is anything else wrong with the carburetor, it is recommended that the entire carburetor be replaced with a new one.

MANIFOLD

PLENUM

GASKET

CARBURETOR

GASKET

Figure 3-6.

8. Reinstall choke link on carburetor and clip the link into the bellcrank.

9. Perform a static governor adjustment. (See “Static Governor

Adjustment”, page 4-2)

10. Start engine and allow to warm up for 5 minutes.

11. Move speed control lever to slow speed position and hold throttle lever against idle stop screw.

12. Adjust the idle top screw to maintain ~1800 RPM idle.

13. Slowly move speed control lever to high speed position.

Note: Be careful not to lose the spring that is located inside the fuel shutoff solenoid when removing the plunger.

CARBURETOR INSTALLATION - VERTICAL SHAFT

1. Slide new carburetor gasket and carburetor onto the studs.

2. Slide new plenum gasket and plenum onto the studs.

3. Install the four nuts and torque to 5.4 Nm (48 in. lbs.).

4. Connect the fuel line and clamp.

5. Reassemble the throttle link to the balljoint on the carburetor.

6. Connect the breather tube and EVAP hose if equipped.

7. Connect the fuel-shutoff solenoid.

Figure 3-7.

Note: The high speed screw may need adjusting to reach the speed control stop without exceeding 3800 RPM.

14. With the speed control in the high speed position, adjust the high speed screw to obtain the desired engine speed. Do not exceed 3800 RPM.

3-2

CLINCHING

SCREW

SECTION 3: CARBURETION AND FUEL SYSTEM

10. Move speed control lever to slow speed position and hold throttle lever against idle stop screw.

11. Adjust the idle stop screw to maintain ~ 1800 RPM idle.

12. Slowly move speed control lever to high-speed position.

IDLE

13. With the speed control in the high speed position, adjust the high speed screw to obtain the desired engine speed. Do not exceed 3800 RPM.

FUEL PUMP

The fuel pump supplied with the engine is a pulse type pump. It uses crankcase vacuum pulses drawn from the valve cover to pump the fuel. It is capable of priming at 12" (30.5 cm) maximum lift, and has a maximum outlet pressure of 1.5 psi. If the fuel pump is not working properly, check the vent hole on the top of the pump for obstructions.

Figure 3.8.

CARBURETOR INSTALLATION – HORIZONTAL SHAFT

1. Install a new carburetor gasket and carburetor onto the studs.

2. Install air cleaner base, breather tube and EVAP hose (if equipped), bolt and nuts and torque to 5.4 Nm (48 in. lbs.).

3. Re-attach choke and throttle links and solenoid wire to carburetor.

4. Install fuel line and fuel line clamp.

5. Install oil fill tube and hold down bolt and torque to 4.7 Nm (40 in. lbs.).

6. Install air cleaner and air cleaner cover.

7. Install yellow knob for Summer/Winter control.

8. Perform a static governor adjustment. (See “Static Governor

Adjustment”, page 4-2)

9. Start engine and allow to warm up for 5 minutes.

If a fuel pump other than the factory recommended pump is used, the fuel line pressure at the carburetor inlet must not exceed 3 psi. Pressures in excess of 3 psi may cause an over rich carburetor mixture that would lead to engine damage.

CARBURETOR

INLET

VENT HOLE

FUEL FROM

TANK

PULSE LINE

Figure 3-9. Fuel Pump

3-3

SECTION 3: CARBURETION AND FUEL SYSTEM

SPRING

RETURN

1 2 3 4 5 6

LOWER

DIAPHRAGM

UPPER

DIAPHRAGM

VENT: UPPER

VENT ASSEMBLY

FUEL

CHECK-

VALVE 1

FUEL

CHECK-

VALVE 2

HARDWARE

Figure 3-10. Fuel Pump Assembly

Fuel Pump Breakdown (see Figure 3-10):

1. Lower Spring Assembly

2. Lower Diaphragm

3. Check Valve Assembly

4. Upper Diagram

5. Upper Vent Assembly

6. Mounting Hardware x 2

As crankcase vacuum is built up the Lower Diaphragm pulls down against the Spring Return and allows fuel to flow through Check-Valve

2. As pressure builds up in the crankcase, the Spring Return pushes up against the Lower diaphragm, allowing fuel will flow through CheckValve 1 and out the fuel port.

LP (LIQUID) - FUEL SYSTEM

Proper service and repair is important to the safe and reli-

able operation of all gaseous fueled engines. Any servicing or testing of a gaseous fueled engine must only be performed by qualified personnel. Always follow applicable installation and service procedures. An example of these requirements is found in NFPA-58 for liquid propane. These are US Federal standards. Worldwide standards vary. Local, city, and state requirements may also have certain requirements that must be observed.

LP (Liquefied Petroleum Gas) is a gaseous fuel and when stored under pressure, becomes a liquid. Although a vapor forms at the top of the tank, this particular system uses a liquid withdrawal method, drawing liquid from the bottom of the tank.

This is accomplished with a special valve that is installed on a normal propane cylinder with a tube that is attached to the valve and extends to the bottom of the storage tank. Pressure in the tank forces liquid propane through the tube when the valve is opened.

The Generac LP system starts with a pressure relief valve to prevent excessive pressure from building in the system during shutdown. This is followed by a 12 volt (normally closed) electric solenoid, which prevents the flow of fuel when the ignition key is off. When the ignition key is turned on, the solenoid opens and allows liquid LP to flow to the regulator.

The liquid fuel vaporizer/regulator converts liquid propane to vapor. The vaporizer/regulator uses either spent engine cooling or engine oil to provide heat to aid in the evaporation process. The vaporizer/regulator controls the vapor supply to an amount required by the engine. The engine’s intake vacuum draws LP into the fuel mixer on an on-demand need. When the engine is off, LP no longer flows from the vaporizer/ regulator to the engine (see Figure 3-32).

TROUBLE SHOOTING

CAUTION! Gaseous fuels are highly explosive; do not use flame

or heat to test the fuel system for leaks. LP gas is heavier than air and tends to settle in low areas; even the slightest spark can ignite these gases and cause an explosion.

Note: Don’t assume that the fuel system is the problem. Verify that the engine has spark and enough compression to start the engine before proceeding with the following steps.

3-4

SECTION 3: CARBURETION AND FUEL SYSTEM

TESTING THE FUEL SHUT-OFF SOLENOID

1. Remove the spark plug wires from each spark plug to prevent accidental starting of the engine.

2. Check for 12 volts DC at the solenoid terminal. See Figure 3-11.

a. Place one hand on the fuel solenoid and turn the ignition switch to

the run position. You should be able to feel the solenoid actuate as well as hear an audible click. Replace the solenoid if it does not actuate. Some systems will delay power to the solenoid until full oil pressure is reached during cranking.

3. If the solenoid is opening properly, proceed to “TESTING AND REPAIRING THE LPG VAPORIZER/REGULATOR.”

4. Reconnect the spark plug leads when finished

COIL BOLT

COIL SPOOL

RESEVOIR BOLT

Figure 3-12. LPG Solenoid Valve Torque and

Lubrication Points

SEALING GASKET

12 VOLT WIRE

Figure 3-11. LPG Solenoid Valve

DISASSEMBLY AND ASSEMBLY OF

LPG SOLENOID VALVE

If the solenoid valve is removed for cleaning or replacing the filter, it is recommended that the special synthetic sealing gaskets be replaced. When installing new sealing gaskets, they should be lubricated using an O-ring lubricant. DO NOT RE-USE O-RINGS!

For improving the functional features and lifetime of the solenoid, it is recommend that the gaskets and filter be replaced after 500 hours of operation.

NOTE: For correct solenoid valve fitting, it is essential that the following torque values be observed:

1 Coil Bolt 7.85 Nm (70 in. lbs.)

2 Reservoir Bolt 11.8 Nm (104 in. lbs.)

3 Coil Spool: 16.6 Nm (147 in. lbs.)

TESTING AND REPAIRING LPG

VAPORIZER/REGULATOR

SPECIAL EQUIPMENT REQUIRED:

1. Air pressure at 100 psi, and air pressure gauge 0-15 psi, with connecting hose and fittings to attach to the 1/8” NPT female pipe connection.

2. Liquid leak detector to check for leaks (recommended).

REPAIR KIT CONTENTS:

(Refer to Parts Manual for specific part numbers.)

Pin, Pivot, Secondary Reg Lever Lever, Assembly Reg Secondary Diaphragm, secondary Assembly. Diaphragm, primary Assembly, Lever, Primary Pin, Pivot, Primary

3-5

SECTION 3: CARBURETION AND FUEL SYSTEM

NOTE: test regulator on engine first or, for scheduled maintenance, proceed to "remove regulator and dismantle as follows".

1. Make sure the fuel tank(s) have an adequate supply of fuel.

2. Make sure the valve on the tank is fully open (turned counterclockwise).

Note: This fuel system is under high pressure.

3. While the fuel is off, install the primary pressure test gauge at the 1/8” primary test port opening at the side of the regulator, marked “PRI”. See Figure 3-14.

4. Disconnect the vapor hose at the Carburetor or Carburetor Adapter.

5. Turn on the ignition to open the fuel solenoid valve.

6. If the engine is equipped with an engine controlled safety switch, bump the starter to make contact and open the fuel solenoid valve.

7. Primary pressure should be 0.5 to 4.5 psi and hold pressure.

8. If primary pressure is too high or too low and leakage is observed at the vapor hose, the regulator must be re-moved, disassembled, cleaned and new parts installed.

REMOVE REGULATOR AND DISASSEMBLE AS FOLLOWS:

Caution! Prior to the removal of any LP system components,

disconnect the battery and turn off the fuel supply at the tank(s).

1. Remove the five secondary cover screws, 10-32 x 0.630”, and lift the cover off the regulator body and secondary diaphragm (see Figure 3-13). The cover has a tendency to stick to the diaphragm and gasket. A slight tap on the edge of the cover with a screwdriver handle or a soft face hammer will loosen the cover.

Note: Do not pry in between the cover and the body. Damage to the sealing surface may result.

2. After the cover has been removed, lift up an edge of the diaphragm. Observe how it is attached to the secondary lever. See Figure 3-14.

Figure 3-13. Remove Five Secondary Cover Screws

4. Remove the four screws, 10-32 x 0.630”, holding the primary diaphragm cover in place. If the cover sticks, use a screwdriver handle or soft-faced hammer to dislodge it. Observe that the longer (2),10-32 x 1.0”, of the six screws are at the top of the cover. Remove primary spring. See Figure 3-16.

3. Remove the two screws, 10-32 x 0.310”, holding the secondary lever pivot pin and remove the secondary lever and spring. The secondary pivot pin is 1.20” long. See Figure 3-15.

PRESSURE TEST POINT

Figure 3-14. Lift Edge of Diaphragm

5. Remove the primary diaphragm. See Figure 3-17.

6. Remove the two screws, 8-32 x 0.375” long. See Figure 3-18.

Note: Remove oil and foreign deposits from all chambers and parts. DO NOT APPLY LIQUID CLEANERS TO THE DIAPHRAGMS AND NEOPRENE FACED VALVES.

3-6

Figure 3-15. Remove Secondary Lever and Spring

SECTION 3: CARBURETION AND FUEL SYSTEM

Figure 3-18. Remove/Replace Two Screws 8-32 x 0.375” long

REASSEMBLY OF REGULATOR:

Figure 3-16. Remove Primary Diaphragm Cover

and Primary Spring

1. Carefully clean and inspect all metal parts-springs, levers, pivot pins and screws. Replace all parts that are included in the repair and rebuilding kits.

2. Carefully clean the body casting and inspect all sealing surfaces. Wipe with a clean rag. Inspect the primary section for foreign materials that might loosen and damage the soft face valves.

3. Blow out the fuel inlet passage and outlet passages. Be sure no foreign material remains in these passages.

4. Inspect the primary orifice and the secondary orifice for nicks scratches or uneven wear.

IMPORTANT! If the primary or secondary seats show any of the above mentioned conditions, the regulator is not rebuildable and must be replaced.

5. Lay the regulator flat on a clean working surface with the primary section up.

6. Replace the primary pivot pin, 0.890”, bridge and two screws, 8-32 x 0.375”. Tighten screws evenly to 30 in. lbs. ±3 in. lbs. (3.39 Nm ± 0.339 Nm). Rock the primary lever assembly to ensure that it pivots freely. See Figure 3-18.

7. Engage the primary diaphragm pin with the slot in the primary lever. Rotate the diaphragm to align the cover screw holes as shown in Figure 3-19.

Figure 3-17. Remove Primary Diaphragm

8. Place primary spring, small side up, on top of diaphragm. Install primary cover and screws. Remember, the 2 longer, 10-32 x 1.0”, screws go to the top of the primary cover. Tighten evenly, in a criss-cross pattern, to 30 in. lbs. ±3 in. lbs. (3.39 Nm ±0.339 Nm). See Figure 3-20.

3-7

SECTION 3: CARBURETION AND FUEL SYSTEM

3-23.

Figure 3-19. Rotate The Diaphragm To Align the

Cover Screw Holes

Figure 3-20. Install Primary Spring, Primary Cover and Screws

9. Place secondary valve spring (5/16” dia. x 5/8’ long) in spring recess near secondary orifice. Replace secondary lever, pivot pin, 1.19” long, and two screws, 10-32 x 0.310”. Make sure the spring fits over the spring boss on the secondary lever. Tighten screws evenly to 30 in. lbs. ±3 in. lbs. (3.39 Nm ± 0.339 Nm). See Figure 3-21.

10. The secondary lever (except for the bent tail tip) should be level or flush with the top of casting. Bend tail end of lever if necessary but do not use excessive force on the rubber valve against the orifice. See Figure 3-22.

11. The secondary lever has a soft valve surface on an aluminum insert which must be swiveled into flat contact with the orifice. Place a pointed instrument in the top indentation of the valve. Apply slight downward pressure and with a gentle rotary motion, swivel the valve into flat contact with the orifice. These valve inserts are not sold separately but are crimped at the factory with proper tension to allow movement but still hold their position. See Figure

Figure 3-21. Install Secondary Valve Spring,

Lever and Pivot Pin

Figure 3-22. Make Sure Secondary Lever is Flush

With Top of Casting

12. Attach primary pressure gauge at the primary pressure test por t opening. See Figure 3-24.

13. Attach air pressure hose to the regulator fuel inlet with approximately 100 psi, ±10 psi air pressure. See Figure 3-25.

14. Slowly depress the secondary lever bent tail end until you are able to detect flow out of the secondary orifice. Let the lever then slowly return to the closed position. Observe the primary pressure reading on the installed gauge. It should be between 0.8 and 2.5 psi. If it is not, recheck your work in the primary fuel section. See Figure 3-26.

3-8

SECTION 3: CARBURETION AND FUEL SYSTEM

Figure 3-23. Positioning Secondary Lever Valve

Figure 3-24. Primary Pressure Test Port Opening

Figure 3-26. Check Primary Pressure Reading

15. Check around the secondary seat for leaks using a liquid leak detector solution. If a leak is detected, repeat Step 11 to insure no leakage at the secondary seat. See Figure 3-27.

Figure 3-27. Check Secondary Seat for Leaks

16. Turn off the air supply. Install the secondary diaphragm by hooking the secondary lever through the center pin. If the screw hole tabs do not line up with the casting, remove and rotate the diaphragm 180 degrees and reinstall. See Figure 3-28.

Figure 3-25. Attach Air Pressure Hose

17. Install secondary cover and align the cover and diaphragm notches. Carefully start all five screws, 20-32 x 0.630”, through cover and diaphragm holes. Tighten evenly, in a criss-cross pattern, to 30 in. lbs. ±3 in. lbs. (3.39 Nm ± 0.339 Nm). See Figure 3-29.

3-9

SECTION 3: CARBURETION AND FUEL SYSTEM

Figure 3-28. Install Secondary Diaphragm

b. Connect LP line(s), reconnect battery and turn on fuel supply at

the tank(s).

c. Turn ignition switch to the "ON" position to verify that the solenoid

is opening.

d. Check all fuel connections with a leak detector. If leaks are pres-

ent, go back to Step 20a.

e. Run the engine until it is at full operating temperature.

21. Repair is now complete.

Figure 3-29. Install Secondary Cover

18. Draw a bubble of leak detector over the “OUTLET” port. The bubble should hold for several seconds with the regulator inlet pressurized. Return to step 10 if the bubble doesn’t hold for several seconds. See Figure 3-30.

19. Remove air pressure supply and primary pressure test gauge. Replace the 1/8” pipe plug in the primary pressure test opening. See Figure 3-31.

20. Install the regulator.

a. Clean all threaded areas and use a commercially available pipe

sealant. Make sure sealant does not get inside of the regulator.

Figure 3-30. Check Outlet Port

Figure 3-31. Re-install Pipe Plug in Test Opening

3-10

MECHANICAL GOVERNOR

DISASSEMBLE:

1. Drain the oil from the engine.

2. Remove any rust, nicks, or burrs from the crankshaft.

3. Remove the four (4) oil cooler screws.

4. Disconnect the wiring from the oil pressure switch.

5. Remove the governor lever from the shaft.

6. Separate the ball joint on the swinging arm.

SECTION 4: GOVERNOR CONTROLS AND GOVERNOR

GOVERNOR

SPOOL

OIL

PASSAGE

O-RING

7. Remove all of the crankcase bolts and slide the crankcase cover off.

8. Discard the crankcase gasket & oil passage o-ring.

GOVERNOR

Both the spool and the flyweights must move freely for the governor to work properly. Check for wear on the spool and flyweights. If wear is noticed, change the governor gear assembly (gear and flyweights), spool, and governor arm. Lubricate all moving parts when reassembling.

GOVERNOR REMOVAL AND INSTALLATION:

1. Leverage gear assembly and governor spool off of governor shaft.

GOVERNOR ASSEMBLY

SPOOL MUST ENGAGE UNDER BOTH FLYWEIGHTS

GOVERNOR GEAR ASSEMBLY

Figure 4-1. Governor Gear Assembly and Spool

2. Remove any remaining plastic from the notch in the governor shaft.

3. Check that all the governor bearing parts (top plate, bearing, and bottom plate) are on the shaft, and that it moves smoothly. (See Figure 4-2)

4. Slide the new gear assembly and spool onto the governor shaft. Slide until the gear hooks into the notch in the governor shaft. (See Figure 4-2)

SPOOL

GOVERNOR GEAR AND FLYWEIGHT ASSEMBLY

PRESS THIS END INTO BLOCK

37 mm

GOVERNOR SHAFT

(37 mm / 1.456” EXPOSED SHAFT)

Figure 4-2. Governor Assembly and Components

4-1

ROLLER BEARING

CUPPED SIDE OF BEARING FACES DOWN

AWAY FROM GEAR

ROLLER BEARING PLATES

SECTION 4: GOVERNOR CONTROLS AND GOVERNOR

GOVERNOR ARM

If the governor arm does not move freely, or if the arm feels loose in the bushings, it may need replacing. If wear is noticed, change the governor arm, governor gear assembly (gear and flyweights), spool, and bushings as needed. Lubricate all moving parts when reassembling.

Figure 4-3. Governor Arm Assembly

DISASSEMBLE GOVERNOR ARM:

1. Remove the e-clips.

2. Slide the arm down and out of the bushings.

3. Replace any parts that appear worn.

Note: The lower bushing is a slip fit, and the upper bushing is pressed in.

ASSEMBLE GOVERNOR ARM:

1. Slide the thrust washer part way onto the new governor arm.

2. Insert the governor arm in the lower bushing holder, and slide it part way in.

3. Install lower e-clip on the arm, and slide the thrust washer down to it.

4. Slip the lower bushing part way on to the arm.

5. Slide the arm in until the thrust washer is tight.

6. Slide the lower bushing down and into it’s holder, then install the upper e-clip.

ASSEMBLE CRANKCASE COVER:

1. Clean any old gasket material from the crankcase and cover mating surfaces.

2. Be sure that the new oil passage o-ring is in place (see Figure 4-1).

TORQUE SEQUENCE FOR

RANKCASE COVER:

-4-5-6-7-8-9-1

1-2-

Figure 4-4. Crankcase Bolt Torque Sequence

4-2

3. Put a new gasket on the crankcase.

SECTION 4: GOVERNOR CONTROLS AND GOVERNOR

Note: On vertical shaft engines, align the camshaft drive and oil pump gerotor.

4. Slide the crankcase cover back on the crankcase.

Note: Hold the governor arm in the counter-clockwise position while installing.

5. Start all of the crankcase bolts, and then torque them to 47.5 Nm (35 ft. lbs.), following the proper torque sequence (see Figure 4-4).

6. Reconnect the ball joint on the swing arm.

7. Place the governor lever on the governor arm. Place the governor spring in the 4th hole out.

8. Perform a static governor adjustment (see below).

9. Reconnect the wires to the oil pressure switch.

10. Reattach the oil cooler to the blower housing.

STATIC GOVERNOR ADJUSTMENT

Determine which version of governor linkage is installed on the engine. Refer to Figures 4-5 (earlier version) and 4-6 (later version).

1. Loosen the clinching screw on the governor lever.

2. Rotate the governor arm clockwise and hold governor lever in WOT (Wide Open Throttle) position.

GOVERNOR LEVER

GOVERNOR ARM

CLINCHING BOLT

Figure 4-6. Static Governor Adjustment (Later Version)

3. While holding this position, torque the clinching screw to 11.3 Nm (100 in. lbs.).

4. Check to make sure that the throttle travels from WOT to IDLE. If it doesn't, the governor needs to be reset again.

IDLE

CLINCHING

SCREW

Figure 4-5. Static Governor Adjustment

Figure 4-7. Dynamic Governor Adjustment (Earlier Version)

DYNAMIC GOVERNOR ADJUSTMENT

1. Start engine and allow to warm up for 5 minutes.

2. Move speed control lever to slow speed position and hold throttle lever against idle stop screw (see Figure 4-7).

3. Adjust stop screw to maintain 1800 RPM idle.

4. Slowly move speed control lever to high-speed position. Do not exceed 3800 RPM (see Figures 4-7 or 4-10 depending on governor version).

Note: On the later governor version, insert an allen wrench or similar object into the hole in the control panel behind the speed control lever. This acts as a temporary stop during adjustment.

Note: The high-speed screw may need adjusting to reach the speed control stop without exceeding 3800 RPM.

5. With the speed control in the high-speed position, adjust the highspeed screw to obtain the desired engine speed (see Figures 4-7 or 4-10 depending on governor version).

4-3

SECTION 4: GOVERNOR CONTROLS AND GOVERNOR

HIGH SPEED SCREW

Figure 4-8. Dynamic Governor Adjustment

(Vertical Shaft)

SPEED CONTROL LEVER

ALLEN WRENCH

Figure 4-9. Dynamic Governor Adjustment

(Horizontal Shaft)

Figure 4-10. Dynamic Governor Adjustment

(Horizontal Shaft)

4-4

SECTION 5: CYLINDER HEAD AND VALVES

OUSING

COOLER

GENERAL INFORMATION

Compression testing information and procedures is described in Section 1, under “Troubleshooting”.

Cylinders are numbered as shown in Figure 5-1.

Note: Cylinder #1 is closest to the flywheel.

Figure 5-1.

REMOVE CYLINDER HEADS

Remove exhaust system from engine. Disconnect choke and throttle control cables. Remove spark plugs.

1. Remove the parts depicted in Figure 5-2.

a. Discard gaskets and valve cover seals.

REMOVE ROCKER ARMS:

1. Unlock jam nuts and remove two ball studs and rocker arm assemblies (see Figure 5-3).

2. Remove push rods and identify each.

Note: Push rods develop a wear pattern. Mixing them from side to side can increase this wear, leading to more frequent adjustments and or loss of performance.

FINGER GUAR

ROTATING SCREE

INTAKE MANIFOLD

EMBL

BLOWER H

PPER WRAPPE

LOWER WRAPPE

VALVE COVE

Figure 5-2.

5-1

SECTION 5: CYLINDER HEAD AND VALVES

BALL STUD

ROCKER ARM

JAM NUT

PUSH ROD GUIDE (TABS MUST FACE UPWARD)

Figure 5-4. Remove Cylinder Head

Figure 5-3.

3. Remove push rod guide plate.

4. Remove head bolts and cylinder head (Figure 5-4).

a. Discard gasket.

5. Repeat Steps 1-4 for other cylinder head.

DISASSEMBLE CYLINDER HEAD

1. Place a shop rag or short section of rubber fuel line under valves inside combustion chamber to hold valve in place while compressing spring.

2. Hold down valve spring retainer with a valve spring compressor (Figure 5-5). Remove the following:

a. Valve spring keepers

b. Valve spring retainer

c. Valve spring

d. Intake and exhaust valves

3. Remove and discard valve stem seals (Figure 5-6).

Figure 5-5. Removing Retainers

VALVE STEM SEAL (USED ONLY ON INTAKE SIDE)

Figure 5-6. Removing Valve Stem Seals

5-2

SECTION 5: CYLINDER HEAD AND VALVES

1/32”

MINIMUM

1.2 MM TO 1.6 MM (3/64” - 1/16”)

SEATING AREA CENTERED

ON VALVE FACE

45° VALVE FACE ANGLE

INSPECT AND REPAIR

1. Check cylinder head (Figure 5-7). Be sure all gasket material is removed from surfaces before checking.

a. Inspect cylinder head for cracks or damage.

b. Use a surface plate or straightedge and check cylinder head

mounting surface for distor tion.

If mounting surfaces are distor ted more than 0.1 mm (.004"), the cylinder head must be replaced.

Note: It is not recommended that cylinder head mounting surfaces be resurfaced.

REFACE VALVES AND SEATS:

1. Valve seats may be reconditioned using a valve seat cutter. If valve seat is wider than dimension shown in Figure 5-9, a narrowing cutter should be used to ensure that contact area of valve seat is centered on face of valve (see Figure 5-10).

a. Use a 60° cutter to narrow seat from bottom and a 15° cutter to

narrow seat from top (Figure 5-9).

Note: If valve seat is loose or cracked, replace cylinder head.

0.8 MM TO 1.2 MM (1/16” - 3/64”)

44°

60° CUTTER

15° CUTTER

2. Clean the valve guides and measure their I.D. using a split ball bore gauge (Figure 5-8).

a. Replace head if either valve guide measures 7.06 mm (0.278 in.)

or more. Valve guides should not be replaced.

SPLIT BALL

BORE GAUGE

Figure 5-7. Check Cylinder Head Distortion

Figure 5-8. Check valve guides

Figure 5-9. Valve Seat Dimensions

2. Valve faces may be resurfaced to 45°. See Figure 5-10 for dimensions for valves.

Note: In most instances it is more economical to replace the valves than to reface them.

Figure 5-10. Valve Dimensions

3. Measure valve stem diameter at specified distance from end of valve, as shown in Figure 5-11.

Replace if less than 6.9 mm (0.272 inches), or if total clearance between valve stem and valve guide exceeds 0.12 mm (0.0047 in).

5-3

SECTION 5: CYLINDER HEAD AND VALVES

1.600” [40 mm]

Figure 5-13. Install Valve Stem Seals

Figure 5-11. Measure Valve Stem Diameter

4. Check valve springs for free length (Figure 5-12).

Replace if free length is less than 36.5 mm (1.437 inches).

Figure 5-12. Check Valve Springs

ASSEMBLE CYLINDER HEAD

1. Install new valve stem seals.

a. Press seal on to intake valve guide bushing until it bottoms (Figure

5-13).

b. Lubricate inner top lip of valve stem seal with oil.

2. Install valves (Figure 5-14).

Note: Lightly coat valve stems with oil before installing valves. Be sure lubricant is not on valve face and seat.

INTAKE VALVE

EXHAUST VALVE

Figure 5-14. Install Valves

3. Place a shop rag or short section of rubber fuel line under valves inside combustion chamber to hold valve in place while compressing spring.

4. Install valve springs and valve spring retainers over valve stems.

5. Compress valve spring and install keepers (Figure 5-15).

5-4

Figure 5-15. Compress valve spring and install keepers

TORQUE SEQUENCE FOR HEADS:

6. Repeat procedure for other valve(s).

SECTION 5: CYLINDER HEAD AND VALVES

ADJUST VALVE CLEARANCE

1. Set No. 1 cylinder at TDC, compression stroke.

a. Adjust rocker arms and check clearance (Figure 5-17).

Valve Clearance (cold) Intake and Exhaust 0.076 mm (.003“).

b. Torque jam nut to 19 Nm (168 in. lbs.).

7. Set push rod guide plate in place with tabs facing upward, and loosely install rocker arm assemblies (ball stud, rocker arm and jam nut).

8. Repeat Step 7 for other head.

INSTALL CYLINDER HEAD

1. Install cylinder head with new gasket.

2. Torque head bolts in sequence shown to 29.9 Nm (22 ft. lbs.) (Figure 5-16).

3. Insert push rods into recess in tappets.

Figure 5-17. Adjust Valve Clearances

2. Set No. 2 cylinder at TDC, compression stroke and repeat Steps 1a and 1b above.

3. Install valve covers with new gaskets.

a. Torque screws to 6.8 Nm (60 in. lbs.).

REASSEMBLE

Install all parts shown in Figure 5-18.

1. Install cylinder wrappers.

a. Torque M5 screws to 2.8 Nm (25 in. lbs).

b. Torque M6 screws to 4.5 Nm (40 in. lbs).

2. Install spark plugs.

a. Torque to 19 Nm (168 in. lbs.).

3. Install exhaust manifold.

a. Torque screws to 19 Nm (168 in. lbs.).

4. Install blower housing.

A-B-C-D-E-

Figure 5-16.

a. Torque screws to 4.5 Nm (40 in. lbs).

5. Install intake manifold with new gaskets.

a. Torque screws to 19 Nm (168 in. lbs.).

b. Assemble governor link to carburetor.

5-5

SECTION 5: CYLINDER HEAD AND VALVES

OUSING

COOLER

6. Install rotating screen.

a. Torque screws to 1.9 Nm (17 in. lbs).

7. Install finger guard.

a. If engine is equipped with hex head screws, torque screws to

4.5 Nm (40 in. lbs).

b. If engine is equipped with finger screws, tighten screws by hand

to approximately 1.3 Nm (12 in. lbs.).

FINGER GUAR

8. Assemble air cleaner.

9. Make Static and Dynamic Governor adjustments as outlined on Page 4-3.

ROTATING SCREE

INTAKE MANIFOLD

EMBL

BLOWER H

PPER WRAPPE

LOWER WRAPPE

VALVE COVE

Figure 5-18. General Assembly

5-6

SECTION 6: ELECTRIC STARTER

GENERAL INFORMATION

The starter motor utilizes a solenoid, similar to an automobile star ter, to assist in pinion gear engagement. When the starter motor is activated, the pinion gear engages a ring gear attached to the engine flywheel and cranks the engine.

Figure 6-1. Starter Motor

TROUBLESHOOTING

NOTE: If a starting problem is encountered, the engine itself should be thoroughly checked to eliminate it as the cause of starting difficulty. It is a good practice to check the engine for freedom of rotation by removing the spark plugs and flywheel guard and turning the crankshaft with a socket and ratchet or breaker bar, to be sure it rotates freely.

WARNING: Do not rotate engine with electric starter while spark

plugs are removed unless using a compression gauge. Arcing at the spark plug ends may ignite the gasoline vapor exiting the spark plug hole.

ENGINE WILL NOT CRANK:

a. Faulty safety interlocks.

b. Discharged or defective battery.

c. Faulty electrical connections.

d. Faulty starter motor switch (open circuit).

e. Open circuit in star ter motor.

f. Brushes sticking, etc.

g. Faulty solenoid.

STARTER MOTOR SPINS BUT DOES NOT CRANK ENGINE:

a. Sticking pinion gear due to dir t.

b. Damaged pinion or ring gear.

c. Battery faulty or damaged.

d. Incorrect rotation due to

counterclockwise viewed from pinion gear.

e. Damaged solenoid

STARTER MOTOR SPINS BUT WILL NOT STOP:

a. Defective star ter switch.

b. Solenoid stuck engaged.

reversed motor

polarity – all motors rotate

TEST EQUIPMENT

DIGITAL MULTIMETER:

A digital multimeter (VOM) may be used to read volts, ohms, amperes and test diodes (rectifiers), Figure 6-2.

NOTE: The Digital Multimeter is equipped with two fuses to prevent damage to the meter in the event that the input limits are exceeded. If the meter displays a reading of 0.00 when testing DC output, check fuses in meter. Refer to VOM operators manual for procedure for checking fuses.

ENGINE CRANKS SLOWLY:

a. Additional load affecting performance (see note above).

b. Discharged battery.

c. Faulty electrical connection (battery circuit).

d. Discharged battery (see alternators).

e. Dirty or worn star ter motor commutator, bearing, weak magnets,

etc.

f. Worn brushes or weak brush spring.

g. Wrong oil viscosity for temperature expected.

h. Battery leads too long or wire too small.

i. Battery too small.

Figure 6-2. Digital Multimeter

6-1

SECTION 6: ELECTRIC STARTER

TEST STARTER MOTOR

TESTING STARTER SOLENOID:

The solenoid is a normally open, electrically activated switch. With the keyswitch in the “START” position, the switch closes, allowing battery current to flow to the star ter motor and crank the engine.

1. The solenoid may be tested while mounted on the engine.

2. A jumper test lead is required for this test.

3. Remove positive battery cable from battery. Then remove battery cable from stud terminal on solenoid.

4. Disconnect wire from tab terminal on solenoid.

5. Keyswitch must be in “OFF” position.

6. Insert red test lead into receptacle in meter.

7. Insert black test lead into

8. Rotate meter selector to position.

9. Attach one meter test lead to each stud terminal on the solenoid (Figure 6-3).

10. Attach one end of jumper lead to positive terminal on battery.

11. Touch jumper wire to tab terminal on solenoid.

receptacle in meter.

is being used. Check the engine manufacturer's Operator's Manual for battery size recommendations.

With the engine and all other accessories turned off, measure the battery voltage across the battery posts using a VOM set to the 20 Volt scale. Do not measure across the the battery wire terminal ends. Voltage should read 12.5 volts or higher.

Do not crank the engine longer than 15 seconds during any of the following tests. To check starter voltage drop:

1. Prevent the engine from starting by either grounding the ignition at the ground stud on the side of the engine or removing the spark plug leads. Using a VOM, place the (+) positive lead on the positive post of the battery. The (-) negative lead on the negative post on the battery. Crank the engine and observe the reading on the VOM.

2. Next, place the (+) positive lead of the VOM on the starter’s battery terminal stud and the (-) negative lead on the starter housing. Crank the engine and observe the VOM reading.

3. Compare the two voltage readings. If the two readings are the same (or a difference of one volt or less) then there is no excessive voltage drop on the positive side. If a voltage drop of greater than one volt is seen, proceed to Step 4.

a. An audible “Click” should be heard as the solenoid switch

“closes.”

b. Meter should make a continuous tone (continuity).

Figure 6-3. Testing Solenoid

CHECKING STARTER VOLTAGE DROP

Before starting this test, make sure the battery is at least 70 percent charged (12.5 volts or higher). Also make sure the correct sized battery

Figure 6-4. Testing Starter Voltage Drop

4. Set the VOM on the 2 volt scale. Place the (+) positive lead on the (+) positive battery post and the (-) negative lead on the (+) positive terminal stud on the starter. Refer to figure 6-4. With the engine still disabled, crank the engine and observe the VOM reading. There should be less than a 0.2 volt drop. If greater, a check of each wire and terminal connection should be made. At each connection, no more than 0.2 volts should be seen.

6-2

SECTION 6: ELECTRIC STARTER

5. Check the (-) negative side of the system. Place the VOM (+) positive lead on the starter case and the other lead on the (-) negative post of the battery. Crank the engine and observe the reading, it should be less than .2 volts.

6. If greater than 0.2 volts, check all wire connections on the (-) negative side of the starter. There should not be any readings higher than 0.2 volts.

STARTER AMP DRAW TEST

This test requires a special tool called a clamp-on type amp meter. Most repair shops should be able to perform this test.

1. Place the amp meter clamp on the (+) positive cable running from the battery (+) post to the starter post.

2. Ground the ignition and crank the engine (no longer than 15 seconds). The starter amp draw should be less than 100 amps during cranking.

Excessive draw could be caused by the following:

•Faulty starter. To verify this, the starter should be removed from

the engine and bench checked prior to replacing. Do an amp draw test on the bench. The starter should not exceed 62 amps with a minimum pinion speed of 3250 rpm. See Figure 6-5.

•Engine oil viscosity too heavy (see engine manufacturer’s Opera-

tors Manual).

•Some equipment manufacturers may use a constant drive pump, which may have too heavy of oil or too tight of belt tension.

•Internal engine problem. Turn the engine over with a socket and ratchet to make sure it turns over easily.

•Battery cable is loose or too small.

•Battery terminals are corroded.

•Battery CCA too low.

BATTERY INFORMATION

A 12 volt battery is required to operate the starter motor on Generac OHVI V-Twin engines. For best starter life and performance, the battery should have a rating of at least 450 cold cranking amps at 0°F for gasoline engines and 525 cold cranking amps for LP engines.

WARNING: Wear eye protection when servicing the battery.

Avoid skin contact. If contact does occur, flush with cold water and consult a physician.

CAUTION: Before servicing battery, disconnect negative (-)

battery cable and then disconnect the positive (+) battery cable.

WARNING: Batteries produce hydrogen, an explosive gas. Do

not store or charge a battery near an open flame or devices which utilize a pilot light or can create a spark.

STARTER

CONTACTOR

STARTER

MOTOR

TACHOMETER

VISE

Figure 6-5. Testing Starter Motor Performance

CLAMP ON

AMP METER

12 VOLT

BATTERY

Figure 6-6. Typical Battery

INSTALLATION:

1. Before installing battery, connect all equipment to be

operated.

6-3

SECTION 6: ELECTRIC STARTER

2. Place battery in holder with flat base. Tighten hold down evenly until snug. DO NOT overtighten.

3. Connect positive terminal to positive post FIRST to prevent sparks caused by accidental grounding. Tighten connectors securely.

4. Connect negative terminal to negative battery terminal. Tighten connectors securely.

CHECKING BATTERY:

1. Physical check – clean if necessary.

a. Corrosion

b. Dirt

c. Terminal and clamps (secure – good condition)

2. Bring battery to full charge.

WARNING: DO NOT exceed charge rate of 1/10 ampere for

every ampere of battery rating. Consult battery manufacturer for maximum charge recommendations.

a. Use a “Trickle” charge (automatically reduces charge

rate).

b. Fill non-sealed battery cells with distilled water after charging

(for batteries that have been in service).

Note: If battery gets “Hot” to the touch or is spitting acid (gassing) excessively, unplug charger periodically.

3. With battery fully charged, check specific gravity readings of each cell with a Battery Hydrometer and record readings (Figure 6-7). All readings should be above 1.250 (compensating for temperature). If specific gravity readings varied 0.50 or if all cells read less than 1.225, replace battery.

USE A TEMPERATURE

COMPENSATED

HYDROMETER

CHECK EACH CELL

AFTER CHARGING

TESTING BATTERY:

Set a digital multimeter to read DC Volts.

Attach RED meter test lead to positive(+) battery terminal. Attach BLACK meter test lead to negative (-) battery terminal. With ignition switch “OFF,” press starter button. If ignition switch and star ter switch are the same switch, disconnect wires from spark plugs and ground ignition using two Ignition Testers. Turn switch to “START.” Meter should display 9 volts or more while cranking engine. If less than 9 volts is measured, replace battery.

CAUTION: Do not crank starter motor for more than 15 seconds

without allowing starter motor to cool at least 2 minutes.

BATTERY RECOMMENDATIONS:

The minimum battery size recommended is 450 CCA @ 0°F for gasoline engines and 525 CCA @ 0°F for LP engines.

BATTERY CABLE RECOMMENDATIONS:

These cable sizes are based on total length of cable from battery positive post to starter, plus ground return to battery negative post.

•#4 AWG — 1.8 meters (6 ft.) or less

•#2 AWG — 3.7 meters (12 ft.) or less

OPTIONAL WIRE HARNESS

Engines supplied with a wire harness have a Packard four or five terminal plug on the harness (see Figure 6-12). A typical wire harness consists of four colored wires as follows:

•A brown wire is used to signal low oil pressure. When low oil pres- sure is detected, this wire becomes a ground. This is a normally open switch. Some engines use a normally closed switch and will work the opposite as stated above.

•A yellow wire is used to ground the ignition. Connect this wire to ground and the ignition will be shut off.

•A white wire is connected to +12 Volts DC and the carburetor solenoid, which allows fuel to flow. Turn off the +12 Volt supply, and the fuel solenoid will close, stopping the flow of fuel.

•An orange wire (red on some models) is used to start the engine. Supply +12 Volts DC to this wire and the starter solenoid will engage. Turn off the +12 volt supply, and the starter will disengage.

Figures 6-8 through 6-10 show the proper connections for the wiring harness and how it is routed.

Figure 6-7. Checking 12 Volt Battery Cells

6-4

FEMALE PACKARD

CONNECTOR

FUSE

SECTION 6: ELECTRIC STARTER

FUSE

FEMALE PACKARD

CONNECTOR

Figure 6-8. Vertical Shaft

Figure 6-10. Horizontal Shaft

Figure 6-9.

Figure 6-11.

6-5

SECTION 6: ELECTRIC STARTER

WIRE HARNESS

(PACKARD CONNECTOR #03138080)

WIRE HARNESS

(PACKARD CONNECTOR #2973422)

5 3 12

LEGEND 1 - IGNITION KILL TERMINAL - YELLOW 2 - STARTER SOLENOID - ORANGE 3 - CARBURETOR FUEL SOLENOID - WHITE 4 - LOW OIL PRESSURE SWITCH - BROWN 5 - OPEN

LEGEND

1. LOW OIL PRESSURE SWITCH - BROWN

2. IGNITION KILL TERMINAL - YELLOW

3. OPEN

4. CARBURETOR FUEL SOLENOID - WHITE

5. STARTER SOLENIOD - ORANGE

WIRE HARNESS

(PACKARD CONNECTOR #2977048)

Figure 6-12. Optional Wire Harness Terminal Identification

LEGEND 1 - IGNITION KILL TERMINAL - YELLOW 2 - BATTERY CHARGER - RED 3 - LOW OIL PRESSURE SWITCH - BROWN 4 - CARBURETOR FUEL SOLENOID - WHITE

6-6

SECTION 6: ELECTRIC STARTER

BATTERY +

BLACK

IGNITION

TO GROUND

SOLENOID

CHARGING SYSTEM

FUSE

30 AMP

SUPPLIED BY

CUSTOMER

DC OUTPUT

WHITE

AC OUTPUT

SUPPLIED BY

CUSTOMER

B+

AC AC

AC OUTPUT

STATOR

VOLTAGE

REGULATOR

CUSTOMER

SUPPLIED BY

SWITCH AND CABLE

CABLE

RED

SUPPLY 12V TO

CRANK ENGINE

12V

BATTERY

SUPPLIED BY

CUSTOMER

SUPPLIED

CUSTOMER BY

Figure 6-13. Typical 12 Volt Wiring Diagram

6-7

LOP

IC - IGNITION COIL

CONNECT TO IGNITION GROUND WIRE TO

GROUND IGNITION ON LOW OIL PRESSURE.

CONNECT TO GROUND SIDE OF A LIGHT OR

BUZZER TO GROUND THE CIRCUIT AND

TURN THE LIGHT OR BUZZER ON WHEN

THERE IS LOW OIL PRESSURE.

KEY:

SUPPLY 12V TO ALLOW FUEL FLOW

FS - FUEL SHUTOFF SOLENOID

SP - SPARK PLUG

SM - STARTER MOTOR

SW - SWITCH, START/STOP

LOP - SWITCH, LOW OIL PRESSURE

NOTES

6-8

SECTION 7:

ALTERNATORS

20 AMP REGULATED ALTERNATOR

The 20 amp regulated alternator system provides AC current through two output leads to the regulator-rectifier. The regulator-rectifier converts the AC current to DC, and regulates the current to the battery. The charging rate will vary with engine RPM and temperature.

The stator, regulator-rectifier and flywheel are NOT interchangeable with any other alternator system.

When checking the alternator components, make the tests in the following sequence:

ALTERNATOR OUTPUT TEST:

Temporarily, disconnect stator wire harness from regulatorrectifier.

1. Insert RED test lead into receptacle in meter.

2. Insert BLACK test lead into receptacle in meter.

3. Rotate selector to (AC volts) position.

CAUTION: ATTACH METER TEST LEADS TO AC OUTPUT TERMI-

NALS (WHITE WIRES) BEFORE STARTING ENGINE. IF STATOR IS GROUNDED (DEFECTIVE), AND METER TEST LEADS CONTACT CENTER DC OUTPUT PIN, ARCING MAY OCCUR WHICH MAY DAMAGE WIRING.

5. With the engine running at 3600 RPM, output should be no less than:

26 Volts AC

6. If no or low output is found, check for bare wires or any other obvious defects. If "shorted" leads are not visible, replace the stator.

TESTING DC OUTPUT CHARGING WIRE:

A simple test may be performed to test the DC output charging wire circuit. If a problem exists in the wiring it can be corrected before testing regulator-rectifier.

Leave stator wire harness disconnected from regulatorrectifier.

Equipment keyswitch must be in OFF position.

1. Insert RED test lead into receptacle in meter.

2. Insert BLACK test lead into receptacle in meter.

3. Rotate selector to (DC volts) position.

4. Attach RED test lead probe to DC output wire terminal (Red Wire), Figure 7-2.

5. Attach BLACK test lead probe to negative battery terminal.

Figure 7-1. Testing AC Output

4. Attach RED and BLACK test lead probes to AC output terminals (white wires), as shown in Figure. 7-1. (Meter test clip leads may be attached to either AC output terminal.)

6. Turn equipment keyswitch to ON position. Meter should display battery voltage.

7. If meter does not display battery voltage, check for blown fuse or broken or shorted wires.

Figure 7-2. Testing DC Output Wire

TESTING REGULATOR-RECTIFIER:

1. Using a digital multimeter, test battery voltage (engine NOT running).

7-1

SECTION 7: ALTERNATORS

2. With the charging system properly connected (all wires reattached to the regulator), start the engine.

3. Bring the engine up to normal operating speed and test the battery voltage again.

4. If the battery voltage while the engine is running is greater than when the engine is stopped, the charging system is working.

CHARGING SYSTEM

B+ STARTER STUD

WHITE

STATOR

WHITE

AC AC

VOLTAGE REGULATOR

B+

SUPPLIED BY CUSTOMER

BATTERY

Figure 7-3. Basic Charging System Schematic

Note: With the engine running, the battery voltage should be at least 13 Volts DC.

BATTERIES

Note: See Section 6 for battery size and cable selection information.

Figure 7-4. 20 Amp Alternator

7-2

DESCRIPTION

The Generac GTH/GTV-760/990 OHVI V-twins use a full pressure lubrication system with an oil filter. The gerotor type oil pump draws oil from a screened oil pickup in the sump and pumps oil through the oil filter.

The filtered oil flows through an oil gallery in the sump and is distributed to the main bearings, connecting rod bearings and camshaft bearings. Engine oil pressure will vary with oil viscosity, ambient air temperature differences, operating temperatures and engine load. Follow the oil recommendation on page 8-2 of this section.

Oil Pressure - @ 70° F (21 ° C):

SECTION 8: LUBRICATION SYSTEM

15 - 50 psi (1.0 - 3.5 Bar)

Two pressure relief valves limit the maximum oil pressure in the system to 60 and 40 psi respectively.

PROTECTION SYSTEMS

LOW OIL PRESSURE SWITCH:

The engine is usually equipped with a normally open type, low oil pressure switch that closes the circuit between the terminals when the oil pressure drops below 8 psi. If one terminal is connected to the ignition ground wire and the other terminal is connected to ground, the engine will shut down on low oil pressure. The switch can also be connected to an alarm or light to indicate low oil pressure, instead of shutting down the engine.

Note: Some engine models have a normally closed type switch and will work the opposite as above.

A delay built into the shutdown system on some engine applications allows oil pressure to build during starting. The delay allows the engine to run for about 10 seconds before sensing oil pressure. If the engine is wired for low oil pressure shutdown and the system senses low oil pressure during operation, the engine shuts down. The engine will not continue to run until 8 psi of oil pressure is reached. If you try to restart the engine within (five) 5 seconds after it shuts down, the engine may NOT start. The system needs 10 seconds to reset.

OIL PRESSURE SWITCH

Figure 8-1. Engine Protective Devices

OIL FILTER

CHECKING THE ENGINE OIL LEVEL

The oil capacity of the GTH/GTV-760/990 OHVI engine is approximately 2 quarts. Refer to the chart on Page 14-1 for the proper amount for each model. To check the engine oil level, proceed as follows:

1. Remove the dipstick and wipe it dry with a clean cloth.

2. Install the dipstick completely; then remove it again. The oil level should be at the “Full” mark. If necessary, add oil until the “Full” mark is reached. DO NOT FILL ABOVE THE “FULL” MARK.

Never operate the engine with the oil level below the “Add”

mark on the dipstick. Doing this could damage the engine.

FILL / CHECK

Figure 8-2. Location of Oil Fill/Check (Vertical Shaft)

8-1

SECTION 8: LUBRICATION SYSTEM

CHANGING THE ENGINE OIL AND FILTER

RECOMMENDED OIL TYPE:

Use only high quality detergent oil rated with an API service classification SN or higher. Do NOT use oil designated "for diesel engines only" (example: CD).

The recommended oil weights include the following:

•During summer months: SAE 30. An acceptable substitute is SAE 10W-30. After first oil change, synthetic oil is acceptable.

•During winter months: SAE 5W-30 or synthetic 5W-30. DO NOT USE SAE 10W-40.

After first oil change, synthetic oil is acceptable.

SAE 30, 10W-30

Synthetic 5W-30

5W-30

DRAIN

Figure 8-3. Oil Drain Location

ROTATE OIL FILTER COUNTER-

CLOCKWISE

TO LOOSEN

Any attempt to crank or start the engine before it has been

OIL CHANGE PROCEDURE:

See "Section 14: Specifications" for crankcase oil capacities. Use no special additives. Make sure that the unit is level when filling with oil. DO NOT OVERFILL.

The engine is equipped with an oil filter. Change the oil and filter after the first eight (8) hours of operation. Change the oil and oil filter every 100 hours thereafter. If you are using this engine under dirty or dusty conditions, or in extremely hot weather, change the oil more often.

Use the following instructions to change the oil while the engine is still warm:

1. Clean the area around the oil drain plug, remove the plug and drain

properly serviced with the recommended oil may result in an engine failure.

the oil completely into a suitable container (Figure 8-3).

Figure 8-4. Removal of Oil Filter

2. When the oil is drained, install and tighten the oil drain plug.

3. When changing the oil filter, use the following instructions:

a. Locate oil filter (Figure 8-4).

b. Place a suitable container beneath the oil filter and turn the

filter counterclockwise to remove the filter.

c. Coat the gasket of a new filter with engine oil. Turn the new

filter clockwise until the gasket contacts the filter adapter, then tighten an additional 3/4 turn.

4. Remove the oil fill cap and insert a clean funnel into the oil fill opening. Fill the crankcase with the recommended oil until the oil level is at the full point on the dipstick.

5. When the crankcase is filled to the proper level, install the oil fill cap. Start engine to fill oil filter, recheck/correct oil level.

8-2

OIL COOLER

All GTH/GTV-760/990 V-Twin engines are equipped with an oil cooler, which is mounted on the blower housing. Forced air from the flywheel fan flows through the oil cooler fins dissipating heat from the engine oil (see Figure 8-5) .

The oil cooler fins should be cleaned every 100 hours (or more often under dusty conditions) and checked periodically for debris. Clean with compressed air or a soft bristle brush.

SECTION 8: LUBRICATION SYSTEM

PUMP BODY

Figure 8-5. Oil Cooler

OIL PUMP

All Generac engines utilize a gerotor style oil pump which is classified as a positive displacement pump. Every revolution of the pump will displace a constant amount of oil. As the inner rotor turns, oil is drawn into the oil intake and fills the entire cavity between the inner and the outer rotor. As the gerotor continues to rotate, oil is moved from the intake port to the outlet port where the oil is pushed under pressure throughout the entire lubrication system (see Figure 8-6).

PRESSURE RELIEF VALVES

When a constant displacement pump is used, a relief valve is necessary to relieve the build-up of pressure in the system. Relief valves are needed because the pump supplies more pressurized oil than the system is able to use.

PICK-UP SCREEN

CAMSHAFT

COLD START RELIEF VALVE (60 psi)

PUMP COVER

INNER ROTOR

OUTER ROTOR

Figure 8-6. Oil Pump, Vertical Engine

Generac uses two relief valves; a "Cold Start" and a "Common" valve. When the oil is cold and the engine is started, the oil pressure can reach up to 140 psi. To avoid damage to the oil filter and oil cooler, the "Cold Start" relief valve is installed in series immediately downstream of the oil pump and is set at 60 psi. After the oil goes through the oil cooler and filter, it flows through the "Common" relief valve. This relief valve is set at 40 psi and mainly regulates the pressure to the PTO journal and throughout the rest of the oil system (Figure 8-7 and 8-8).

8-3

COMMON RELIEF VALVE (40 psi)

Figure 8-7. Oil Pump, Horizontal Engine

PICK-UP SCREEN

SECTION 8: LUBRICATION SYSTEM

The components of both pressure relief valves are identical. The difference in pressure is determined by the depth of the hole in which the assembly is installed.

CAP

RELIEF SPRING

RELIEF BALL

CAMSHAFT BOSS

OIL PUMP DRIVE

OIL PUMP COVER

COLD START RELIEF VALVE (60 psi)

Figure 8-8. Typical V-twin Engine Oil Flow (Vertical Shaft Engine Shown)

OIL PUMP PICK-UP SCREEN

COMMON PRESSURE RELIEF VALVE (40 psi)

8-4

SECTION 9: ENGINE DISASSEMBLY

ENGINE DISASSEMBLY

Drain oil, disconnect the wire harness,connector, cables and fuel hose. Remove engine from equipment. Remove intake and exhaust systems. Remove engine shroud and all cylinder wrappers. Disconnect stop switch wires at ignition coils and remove ignition coils (see Section

2). Remove cylinder heads (see Section 5).

1. Remove the following parts (Figure 9-1):

a. Flywheel b. Breather Assembly

c. Charging coil d. Backplate

e. Starter Motor

2. Remove crankcase cover/sump.

a. Discard gasket and O-ring.

1. Fan Retainer

2. Fan

3. Flywheel

4. Charging Coil

5. Backing Plate

6. Ignition Coils

7. Breather

8. Starter

9. Cylinder Head

10. Tappets

11. Push Rods

12. Crankcase Cover

13. Camshaft

14. Connecting Rod

15. Piston Assembly

16. Crankshaft

3. Rotate crankshaft and camshaft until timing marks align and remove camshaft (Figure 9-2).

Note: If necessary, place the engine flywheel side down to prevent tappets from catching on the camshaft.

a. Remove tappets.

Note: Remove any carbon or ridge at the top of the cylinder bores to prevent breaking rings when removing piston and connecting rod assemblies.

4. Remove No. 2 connecting rod cap and push connecting rod and piston assembly out through top of cylinder (Figure 9-3).

a. Reassemble cap to rod to prevent interchanging.

Figure 9-1. Partial View of Engine Breakdown

9-1

SECTION 9: ENGINE DISASSEMBLY

Figure 9-2. Remove Camshaft

Note: Clean all surfaces of gasket material. Remove oil seals and thoroughly clean components in solvent. Organize components, keeping parts which are assemblies together.

Figure 9-3. Remove Pistons and Connecting Rods

5. Repeat for cylinder #1.

6. Remove crankshaft (Figure 9-4).

7. Remove oil pump from crankcase cover/sump.

Figure 9-5. Remove Oil Pump (Vertical Shaft Engine)

Figure 9-4. Remove Crankshaft

PICK-UP SCREEN OIL PUMP

Figure 9-6. Remove Oil Pump (Horizontal Shaft Engine)

9-2

CHECK CRANKCASE

Check crankcase for cracks, stripped threads or broken fins. Check cylinder bores for damage or scoring.

1. Check cylinder head mounting surface for distor tion with a straight edge, Figure 10-1.

If mounting surfaces are distor ted more than 0.1 mm (.004"), the crankcase must be replaced.

SECTION 10: CYLINDER & CRANKCASE COVER

Figure 10-2. Check Cylinder Bore

Figure 10-1. Checking Cylinder Head Mounting Surface

2. Check cylinder bores for wear using a cylinder bore gauge or a telescoping gauge and dial caliper.

Standard Bore Size: 90.00-90.025 mm (3.543-3.544”)

a. Measure cylinder bore in 6 points at right angles as shown,

Figures 10-2 and 10-3.

b. If cylinder bore is worn more than 0.075 mm (.003") or more

than 0.035 mm (.0015") out of round, it must be replaced.

NOTE: If cylinder bores are within specification and show no signs of scoring or other damage, new piston rings may be installed providing the cylinder bores are reconditioned using a rigid hone with finishing stones to restore the proper cross hatch angle in the cylinder bores. The proper cylinder cross hatch ensures proper lubrication and piston ring break in.

Refer to "Cylinder Finish (Cross Hatch)” for correct procedure for cross hatch honing.

RESIZING:

Note: Oversize rings and pistons are NOT available. DO NOT bore or over hone cylinder.

TOP

CENTER

BOTTOM

Figure 10-3. Measure at Six Points

CYLINDER FINISH (CROSS HATCH):

It is recommended that the cylinder bores be reconditioned to restore the cross hatch when new piston rings are to be installed in a cylinder that is within specification. Be careful not to hone oversize or it will be necessary to replace the crankcase.

Special honing stones are required when reconditioning a cylinder bore. Honing stones will produce the correct cross hatch necessary for proper lubrication and ring seating. Honing is accomplished in a two step process called plateau honing. These steps must be followed carefully and should be performed by a competent machine shop. The correct cross hatch angle is approximately 45 degrees, Figure 10-4.

Honing is done with a variable speed 1/2", portable drill and a honing fixture. See Figure 10-10 for dimensions to make a honing fixture. Use two crankcase cover mounting screws to fasten the crankcase to the honing fixture, Figure 10-5.

10-1

SECTION 10: CYLINDER & CRANKCASE COVER

Cut a wood block and place inside crankcase to prevent hone from extending further than 3/4" to 1" (19 mm to 25 mm) below cylinder bore.

Clamp honing fixture and crankcase securely in a vise at a convenient work height.

Place hone in middle of cylinder bore. Tighten adjusting knob with finger until stones fit snugly against cylinder wall. DO NOT FORCE. Place hone drive shaft in chuck of portable drill and tighten. Be sure that cylinder and hone are centered and aligned with the drill spindle.

NOTE: The first step in plateau honing requires a 220 grit diamond metalbond superabrasive stone (such as a Sunnen GMG55). Drill speed should be 240 RPM at 80 strokes per minute. Lubricate cylinder liberally to prevent build up on the honing stones. The second step requires a 800 grit diamond metalbond superabrasive stone (such as a Sunnen RMG807) at 110 RPM drill speed at 80 strokes per minute.

NOTE: Sunnen lubricating oil (SCC605) is recommended. Automatic transmission fluid is also an acceptable honing oil. Another acceptable honing oil can be made by mixing 4 parts 30 weight oil with 1 part kerosene.

Honing grit is highly abrasive and will cause rapid wear to all of the internal components of the engine unless it is completely removed.

Figure 10-5. Honing Cylinders

NOTE: When cylinder and crankcase have been thoroughly cleaned, use a clean white rag or napkin and wipe the cylinder bore. If honing grit is present it will appear as a gray residue on rag. If any honing grit is evident, re-wash and rinse entire cylinder and crankcase and check again. When there is no trace of honing grit on the rag, the cylinder is properly cleaned. Then oil cylinder bore to prevent rusting.

45º

Figure 10-4. Cylinder Cross Hatch

CLEANING:

It is very important that the entire cylinder and crankcase be thoroughly cleaned after honing.

First wash the cylinder and crankcase carefully in a commercial solvent or kerosene. Then thoroughly wash cylinder and crankcase using a stiff brush with soap and hot water. Rinse thoroughly with hot running water. Repeat washing and rinsing until all traces of honing grit are gone.

CHECK MAGNETO (FLYWHEEL END) BEARING:

Check magneto bearing for damage. Damaged bearings cannot be replaced. If not damaged, check for wear using a telescoping gauge and caliper (see Figure 10-6). Measure at several locations. If the measured diameter is larger than 38.25 mm (1.506”), the must be replaced.

The diameter of the crankshaft may also make it necessary to replace the

crankcase

BEARINGS

crankcase

. See Section 14 for the crankshaft measurement details.

10-2

Figure 10-6. Check Magneto Bearing

CHECK PTO BEARING

The sump cover must be replaced if the bearing is damaged or if it measures larger than 42.25mm (1.663”) in diameter (see Figure 10-7).

SECTION 10: CYLINDER & CRANKCASE COVER

CHECK CAMSHAFT BEARINGS

Use a telescoping gauge and caliper to check camshaft bearings. If camshaft bearings are worn, crankcase or crankcase cover must be replaced. (For vertical shaft engines, the oil pump cover must be replaced). See Figures 10-8 and 10-9.

TELESCOPING

GAUGE

The diameter of the crankshaft may also make it necessary to replace the sump cover. See Section 14 for the crankshaft measurement details.

Figure 10-7. Check PTO Bearing

INSTALL PTO OIL SEAL:

Install a new PTO oil seal and press it in until it is 1.5mm (1/16”) below the mounting surface.

Figure 10-8. Checking PTO Side Camshaft Bearing

TELESCOPING

GAUGE

Figure 10-9. Checking Magneto Side Camshaft Bearing

OIL SEALS:

Always install new oil seals whenever engine is disassembled for major servicing. Lubricate sealing edge of oil seal with clean engine oil before assembly.

10-3

SECTION 10: CYLINDER & CRANKCASE COVER

OOD

]

216mm [8.504"

16.5mm [0.65"

183.5mm [7.224"

17mm [0.67"

MATERIAL: W

25.4mm [1"] x 216mm [8.5"] x 254mm [10.0"

10.5mm [0.413"

12mm [0.473"] TY

254mm [10.0"

CLAMP THIS END IN VI

Figure 10-10. Honing Fixture

10-4

SECTION 11: CRANKSHAFT & CAMSHAFT

CHECK CRANKSHAFT:

Inspect crankshaft threads, keyways and timing gear for damage or wear. If threads, keyways or timing gear are damaged or worn, replace crankshaft. Check journals for scoring. If journals are scored, replace crankshaft. Check journals for wear. See crankshaft reject sizes in Section 14.

MAGNETO

JOURNAL

FLYWHEEL

KEY

OIL

GALLERY

OIL

GALLERIES

CRANKPIN

PTO

JOURNAL

TIMING

GEAR

Figure 11-1. Check Crankshaft

CHECK CAMSHAFT:

Inspect gear teeth, lobes and journals for wear and nicks (see Figure 11-2). Check journals and lobes for scoring and wear. Replace camshaft if not to specification noted in Section 14.

INTAKE

MAGNETO

JOURNAL

LOBES

EXHAUST

LOBES

PTO

JOURNAL

Figure 11-2. Check Camshaft

11-1

NOTES

SECTION 12: PISTON, RINGS & CONNECTING ROD INSPECTION & ASSEMBLY

GENERAL INFORMATION

It is recommended that new piston rings be installed whenever the engine is disassembled for major servicing or overhaul, providing that cylinder bores are within specification.

Measure cylinder bores before checking pistons and rings. See Section 10. If cylinder bores are out of tolerance, a new crankcase will be needed.

If the cylinder bore is more than .075 mm (.003") oversize, or 0.035 mm (0.0015") out of round, it must be replaced.

DISASSEMBLE PISTON AND CONNECTING ROD

1. Remove piston compression rings using a ring expander similar to the one shown in Figure 12-1.

a. Then remove oil ring.

2. Disassemble piston from connecting rod, Figure 12-2.

a. Remove piston pin locks.

b. Piston pin is a slip fit in piston and connecting rod.

Keep pistons and connecting rods together as an assembly. Do not mix.

CHECKING PISTON AND RINGS

If the cylinder is not going to be replaced and the piston shows no signs of scoring, the piston should be checked. Carefully remove carbon from ring grooves.

1. Check side clearance of ring grooves using new rings, Figure 12-3. If a 0.10mm (0.004”) feeler gauge for the compression rings or

0.20mm (0.008”) for the oil ring can be inserted, the ring groove is worn. The piston must be replaced.

Figure 12-1. Remove Rings

Figure 12-2. Remove Piston Pin Locks

Figure 12-3. Check Ring Grooves

2. Check ring end gap, Figure 12-4.

a. Using a new ring, insert approximately 1" (25 mm) into cylinder.

b. If gap is less than the standard dimension, remove some mate-

rial from the end of the ring with a very fine file to achieve the minimum gap.

3. Check piston pin bore, Figure 12-5.

a. Replace if greater than 20.03mm (.7886") or if it is 0.01mm

(0.0005") out of round.

12-1

SECTION 12: PISTON, RINGS & CONNECTING ROD INSPECTION & ASSEMBLY

Figure 12-4. Checking Ring End Gap

Figure 12-5. Check Piston Pin Bore

CHECKING PISTON PIN AND CONNECTING ROD

1. Check piston pin, Figure 12-6.

a. Replace if less than 19.97mm (.7862") or if it is .01mm (.0005")

out of round.

2. Check connecting rod bearings (see Figure 12-7).

Note: If piston pin or crankpin bearing ends are scored or worn the connecting rod must be replaced.

Figure 12-6. Check Piston Pin

CRANKPIN BEARING

PISTON PIN BEARING

Figure 12-7. Check Rod Bearings

ASSEMBLE PISTON AND CONNECTING ROD

Lubricate parts with engine oil and assemble #1 piston and connecting rod, Figure 12-8.

1. Notch or casting mark on the piston top must face towards the flywheel.

2. Number "1" on connecting rod must face PTO side (opposite notch or casting mark on piston).

a. Install piston pin locks with needle nose pliers.

Lubricate parts with engine oil and assemble #2 piston and connecting rod, Figure 12-9.

1. Notch or casting mark on the piston top must face towards the flywheel.

2. Number "2" on connecting rod must face PTO side (away from the flywheel).

a. Install piston pin locks with needle nose pliers.

12-2

SECTION 12: PISTON, RINGS & CONNECTING ROD INSPECTION & ASSEMBLY

CASTING MARK MUST FACE FLYWHEEL SIDE

NUMBER MUST FACE PTO SIDE

Figure 12-8. Assemble #1 Rod And Piston

ASSEMBLE PISTON RINGS TO PISTON

Install piston rings using ring expander when installing center and top compression rings. See Figure 12-10.

1. Install oil ring expander.

a. Install lower oil scraper ring.

a. Install upper oil scraper ring.

2. Install center compression ring with dimple up.

CASTING MARK MUST FACE FLYWHEEL SIDE

Figure 12-9. Assemble #2 Rod And Piston

PISTON

RING

GROOVES

NUMBER MUST FACE PTO SIDE

TOP COMPRESSION RING

(DIMPLE MUST FACE UP)

CENTER COMPRESSION RING

(DIMPLE MUST FACE UP)

OIL RING EXPANDER

AND SCRAPER RINGS

3. Install top compression ring with dimple up.

DIMPLE DENOTES UP-SIDE OF RING. (TOW ARDS T OP OF PISTON)

Figure 12-10. Piston Ring Installation

0.25-0.50 mm

(0.0098-0.0197 in.)

12-3

NOTES

INSTALL CRANKSHAFT

Lubricate magneto bearing and inside edge of oil seal with engine oil and install crankshaft.

SECTION 13: ENGINE ASSEMBLY

RING

COMPRESSOR

Figure 13-2. Compressing Rings

Figure 13-1. Installing Crankshaft

INSTALL PISTON AND CONNECTING ROD

Note: Install #1 piston and connecting rod first.

1. Lubricate piston rings, piston skir t, and Ring Compressor, with oil.

a. Rotate the rings so that the ring end gaps are 90 degrees from

each other.

b. Place piston inside of ring compressor and set upside down on

bench with projections on compressor facing up Figure 13-2.

c. Tighten ring compressor until rings are fully compressed.

d. Remove connecting rod cap.

2. Lubricate cylinder bores and crankpin and rotate crankshaft until it is at bottom of stroke.

3. Install #1 piston with notch or casting mark towards flywheel side. See Figure 13-3.

a. Push piston down by hand, or with a wood handle, until

connecting rod is seated on crankpin.

4. Assemble connecting rod cap to rod with match marks aligned, Figure 13-4.

HAMMER HANDLE

NOTCH OR CASTING MARK TOWARD FLYWHEEL SIDE

Figure 13-3. Installing Piston And Connecting Rod

ALIGN MARKS ON ROD AND CAP WHEN ASSEMBLING

a. Torque screws to 24.4 Nm (216 in. lbs.).

5. Rotate crankshaft two revolutions to check for binding. Rod should also be free to move sideways on crankpin.

Repeat Steps 1-5 for #2 cylinder.

Figure 13-4. Torque Connecting Rods (#2 rod shown)

13-1

SECTION 13: ENGINE ASSEMBLY

Note: The number 1 on #1 connecting rod and the number 2 on #2 connecting rod must be facing PTO side.

Important: Failure to use a torque wrench can result in loose connecting rod screws causing breakage or tight connecting rod screws causing scoring.

INSTALL CAMSHAFT

Lubricate tappets, camshaft journals and lobes with engine oil.

1. Install tappets.

2. Align timing marks on camshaft and crankshaft gear and install camshaft, Figure 13-5.

3. Assemble governor spool to governor shaft.

a. Make sure that spool engages flyweights, Figure 4-2.

b. Clean all old gasket material from crankcase and cover.

c. Install new oil passage o-ring in crankcase, Figure 13-6.

Figure 13-7. Installing Oil Pump

INSTALL CRANKCASE COVER

Lubricate PTO seal and cam gear bearing.

TIMING MARKS

Figure 13-5. Installing Camshaft

Figure 13-6. Crankcase Oil Passage O-ring

INSTALL OIL PUMP

1. Lubricate inner and outer gerotor and set in place.

2. Install oil pump cover.

3. Torque screws to 12.2 Nm (108 in. lbs.). See Figure 13-7.

OIL

PASSAGE

O-RING

1. Rotate governor shaft counterclockwise so that the paddle rests against the oil pump pick-up, Figure 13-8.

2. Rotate the inner gerotor so it aligns with the camshaft drive.

Figure 13-8. Rotating Governor Shaft

3. Install crankcase cover with new gasket.

Note: If the oil pump drive is not aligned, the cover will not slide completely on. Turning the crankshaft may align the oil pump drive.

4. Install governor support bracket.

a. The allen head crankcase bolt may need to be backed

off.

5. Torque screws in sequence shown to 47.5 Nm (35 ft. lbs.), Figure 13-9.

6. Check crankshaft end play. If less than 0.05mm (.002”) there may be an assembly problem.

13-2

SECTION 13: ENGINE ASSEMBLY

3. Assemble ignition coils to engine, Figure 13-11.

a. Mounting holes in coil are slotted. Push coil as far back as pos-

sible and tighten one screw to hold coil in place.

4. Repeat for second coil.

Note: The spark plug lead must be at the top.

5. Install ground wire onto tab terminal on ignition coils.

TORQUE SEQUENCE FOR

CRANKCASE COVER:

1-2-3-4-5-6-7-8-9-10

Figure 13-9. Crankcase Cover Torque Sequence

INSTALL ALTERNATOR AND IGNITION COILS

1. Install alternator, Figure 13-10.

a. Torque screws to 4.75 Nm (40 in. lbs.).

BACK PLATE RELIEF

and under breather tube.

6. Install starter motor.

a. Torque screws to 27 Nm (228 in. lbs.).

Important : Make sure wires are routed over coil mounting posts

SPARK PLUG LEAD AT TOP

GROUND WIRE ROUTING

Figure 13-11. Ignition Coils

INSTALL BREATHER

1. Insert baffle if equipped.

2. Insert breather material.

3. Install breather assembly and gasket.

4. Torque bolts to 4.75 Nm (40 in. lbs.).

Figure 13-10. Install Alternator

2. Install back plate.

a. Torque screws to 4.75 Nm (40 in. lbs.).

Important: Route alternator wires through relief in back plate. DO NOT pinch wires.

INSTALL FLYWHEEL

Important: Clean flywheel and crankshaft taper removing all oil, dirt or grease.

1. Insert flywheel key into crankshaft.

2. Assemble flywheel to crankshaft.

3. Install washer (cupped side down) and flywheel nut.

4. Torque flywheel nut to 214 Nm (150 ft. lbs.), Figure 13-12.

13-3

SECTION 13: ENGINE ASSEMBLY

a. Torque head bolts in sequence shown (Figure 13-14) to 29.9 Nm

(22 ft. lbs.).

3. Insert push rods into recess in tappets.

Figure 13-12. Torque Flywheel Nut

ADJUST IGNITION COIL AIR GAP

1. Rotate flywheel until magnet is under coil laminations.

2. Place 0.20-.30mm (.008"-.012") thickness, non-magnetic gauge between magnet and coil laminations, Figure 13-13.







CYLINDER HEAD TORQUE SEQUENCE:

A-B-C-D-E-F

Figure 13-14. Cylinder Head Torque







INSTALL ROCKER ARMS

1. Lubricate rocker arms and ball studs with clean engine oil.

2. Assemble ball studs, rocker arms, jam nuts and guide plates (with tabs facing up) to cylinder head, Figure 13-15.

Figure 13-13. Adjust Coil Air Gap

3. Loosen mounting screw so magnet will pull coil down against thickness gauge.

a. Torque screws to 4.75 Nm (40 in. lbs.).

4. Rotate flywheel to remove thickness gauge.

5. Repeat Steps 1 through 4 for second coil.

INSTALL CYLINDER HEADS

1. Install cylinder head with new gasket.

2. Lubricate threads of head bolts with one drop of oil.

a. Make sure that the push rods are in the proper location on the

tappets and the rocker arms.

STUD

ROCKER ARM

GUIDE PLATE (WITH TABS FACING UP)

NUT

Figure 13-15. Install Rocker Arms

13-4

ADJUST VALVE CLEARANCE

1. Set No. 1 cylinder at TDC (Top Dead Center), compression stroke.

a. Adjust rocker arms to specified clearance, Figure 13-16.

Valve Clearance (cold) INTAKE and EXHAUST:

0.076mm, +/- 0.02mm (.003" +/- .001")

b. Torque ball stud jam nuts to 19 Nm (168 in. lbs.).

2. Repeat for No. 2 cylinder.

3. Install valve covers with new gaskets, Figure 13-17

a. Torque bolts to 6.8 Nm (60 in. lbs.).

BALL STUD

SECTION 13: ENGINE ASSEMBLY

VALVE COVER

GASKET

JAM NUT

Figure 13-16. Adjust Valve Clearance

FINGER GUARD

ROTATING SCREEN

INTAKE MANIFOLD

ASSEMBLY OIL COOLER

BLOWER HOUSING

UPPER WRAPPER

LOWER WRAPPER

VALVE COVER

0.076 mm

(0.003") GAUGE

Figure 13-17. Install Valve Covers and Gaskets

GENERAL ASSEMBLY

1. Install cylinder wrappers.

a. Torque M5 screws to 2.8 Nm (25 in. lbs.).

Figure 13-18. Install Blower Housing

13-5

SECTION 13: ENGINE ASSEMBLY

b. Torque M6 screws to 4.5 Nm (40 in. lbs.).

c. Connect ignition ground wire to ignition ground terminal in

backing plate (see Figure 13-19).

d. Connect all remaining wires to their proper locations.

GROUND TERMINAL

Figure 13-19. Ground Terminal

2. Assemble governor lever to governor arm. DO NOT tighten at this time.

3. Install speed adjust assembly (refer to Section 4).

a. Torque screws to 6.0 Nm (53 in. lbs.).

4. Install exhaust.

5. Install fan and retaining ring.

a. Torque screws to 21.7 Nm (192 in. lbs.).

6. Install blower housing.

a. Torque screws to 4.5 Nm (40 in. lbs.).

7. Install rotating screen.

a. Torque screws to 1.9 Nm (17 in. lbs.).

8. Install intake manifold assembly.

a. Torque bolts to 19 Nm (168 in. lbs.).

9. Install finger guard.

a. Tighten screws by hand to approximately 1.3 Nm (12 in-lbs).

10. Connect governor linkage and speed control linkage (refer to Section 4).

11. Install spark plugs.

a. Torque spark plugs to 19 Nm (168 in. lbs.).

ADJUST GOVERNOR

Note: Refer to Section 4, Page 4-3 for Static Governor Adjustment.

WARNING: BEFORE STARTING OR RUNNING ENGINE, static

adjustment of the governor must be completed! Failure to make the static adjustments first could result in engine overspeeding which may result in engine damage, property damage or personal injury.

a. Torque screws to 19 Nm (168 in. lbs.).

13-6

SECTION 14: SPECIFICATIONS

GENERAL SPECIFICATIONS

MODEL GTH & GTV 760 GTH & GTV 990 GTH & GTV 1000

Bore 90 mm (3.54”) 90.00 mm (3.54”) 90.00 mm (3.54”)

Stroke 60 mm (2.36”) 78 mm (3.07”) 78.58 mm (3.09”)

Displacement 763cc 992cc 999cc

OIL CAPACITY GTV 760/990/1000 GTH 760/990/1000

With Oil Filter* 2.3L (2.4 qt) 2.2L (2.3 qt)

Without Oil Filter* 2.0L (2.1 qt) 1.9L (2.0 qt)

* To prevent over filling of the crankcase, add approximately 3/4 of the total volume when refilling and then add as needed to bring the level up to

the full mark.

COMMON SPECIFICATIONS

Ignition Coil Air Gap .008” – .012” (0.20 – 0.30 mm) Crankshaft End Play .002” – .015” (0.05 – 0.40 mm) Spark Plug Gap .040” (1.01 mm) Valve Clearance (Cold)

– Intake .002” – .004” (0.05 – 0.10 mm) – Exhaust .002” – .004” (0.05 – 0.10 mm)

Normal Compression

– GTH/GTV-760 130-160 psi – GTH/GTV-990/1000 160-190 psi

Alternator (to crankcase) Screws 4.75 Nm (40 in. lbs.) Ignition Coil Screws 4.75 Nm (40 in. lbs.) Carburetor Adaptor Mounting Bolts 5.4 Nm (48 in. lbs.) Connecting Rod Bolts 24.4 Nm (216 in. lbs.) Crankcase Cover Bolts 47.5 Nm (35 ft. lbs.) Cylinder Head Bolts 29.9 Nm (22 ft. lbs.) Exhaust Manifold Bolts 19 Nm (168 in. lbs.) Flywheel Nut 214 Nm (150 ft. lbs.) Flywheel Fan Retainer Bolts 21.7 Nm (182 in. lbs.) Governor Lever (clinching screw) 11.3 Nm (100 in. lbs.) Intake Manifold Screws 19 Nm (168 in. lbs.) Oil Pump Cover 12.2 Nm (108 in. lbs.) Rocker Arm Jam Nut 19 Nm (168 in. lbs.) Spark Plug 19 Nm (168 in. lbs.) Starter Motor Bolts 27 Nm (228 in. lbs.) Rocker Cover Screws 6.8 Nm (60 in. lbs.) Blower Housing Screws 4.75 Nm (40 in. lbs.)

TORQUE SPECIFICATIONS

14-1

SECTION 14: SPECIFICATIONS

STANDARD AND REJECT DIMENSIONS

DESCRIPTION STANDARD DIMENSION REJECT DIMENSION

CYLINDER:

Bore 90.00 – 90.025 mm (3.543” – 3.544”) 90.10 mm (3.547”)

Out of Round 0.035 mm (.0015”)

Main Bearing (Mag End) 38.044 – 38.099 mm (1.498” – 1.5”) 38.25 mm (1.506”)

Cam Bearing 20.00 – 20.03mm (.787” – .789”) 20.06 mm (.790”)

CYLINDER HEAD:

Valve Guide 7.005 – 7.020 mm (.2758” – .2764”) 7.06 mm (0.278”)

Valve Stem 6.945 – 6.98 mm (.2734” – .2748”) 6.9 mm (0.272”)

Valve Spring Free Length 38.0 – 36.5 mm (1.49" – 1.43") less than 36.5 mm (1.437")

CRANKCASE COVER:

Main Bearing (PTO End) 42.044 – 42.099 mm (1.6553” – 1.6574”) 42.25 mm (1.663”)

Cam Bearing 18.0 – 18.025 mm (.7087” – .7096”) 18.06 mm (.711”)

CRANKSHAFT:

Crankpin GT1000 41.00 - 40.08 mm (1.614" - 1.577") 40.05 mm (1.576")

Crankpin GT760/990 38.99 – 39.01 mm (1.535” – 1.536”) 38.96 mm (1.534”)

Magneto Journal 38.00 – 38.012 mm (1.496” – 1.4965”) 37.85 mm (1.490”)

PTO Journal 42.00 – 42.012 mm (1.6535” – 1.654”) 41.85 mm (1.648”)

CAMSHAFT:

Magneto Journal

PTO Journal 17.964 – 17.982 mm (.7072” – .708”) 17.93 mm (.705”)

Lobes 31.239 – 31.479 mm (1.2299” – 1.2393”) 31.02 mm (1.221”)

CONNECTING ROD:

Crankpin Bearing GT1000 41.06 - 41.07 mm (1.6165" - 1.6169") 41.09 mm (1.6177")

Crankpin Bearing GT760/990 39.06 – 39.07 mm (1.5378” – 1.5382”) 39.09 mm (1.539”)

Piston Pin Bearing 20.02 – 20.03 mm (.7882” – .7886”) 20.05 mm (.7894”)

PISTON PIN:

Diameter 19.984 – 19.995 mm (.7868” – .7872”) 19.97 mm (.7862”)

Out of Round 0.01 mm (.0005”)

PISTON PIN BEARING (PISTON):

Bore 20.00 – 20.02 mm (.7874” – .7882”) 20.03 mm (.7886”)

Out of Round 0.01 mm (.0005”)

PISTON RINGS:

End Gap – Top & Center 0.25 – 0.5 mm (.0098” – .0197”) 0.75 mm (.0295”)

End Gap – Oil 0.38 – 1.15 mm (.015” – .045”) 1.5 mm (.059”)

Ring Side Clearance – Top & Center 0.04 – 0.09 mm (.0016” – .0035”) 0.10 mm (.004”)

Ring Side Clearance – Oil 0.012 – 0.18 mm (.0005” – .007”) 0.20 mm (.008”)

14-2

NOTES

Part No. 0F6923 Printed in USA Rev. D 10/24/12 ©2012 Generac Power Systems, Inc. All rights reserved. Specifications are subject to change without notice No reproduction allowed in any form without prior written consent from Generac Power Systems, Inc.

Generac Power Systems, Inc.

S45 W29290 Hwy. 59

Waukesha, WI 53189

1-888-GENERAC

(1-888-436-3722)

generac.com

Generac Power Systems GTH760, GTH990, GTV990, GTV1000, GTH1000 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual