Generac GTV990/760 V-Twin OHVI Engine Workshop Service Repair Manual

SERVICE MANUAL Manual Part No. 0E2081 Printed in U.S.A P.O. Box 297 • Whitewater, WI • 53190 Phone: (262) 473-5514 Fax: (262) 472-6505 GTV – 990/760 V-TWIN OHVI ENGINE Draft Approved- 04/24/03 chodina@live.co.uk chodina@live.co.uk

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 trou- bleshooting, testing, service and repair procedures recommended by GENERAC ® POWER SYSTEMS, INC. and described in this manual are effective methods of performing such operations. Some of these operations or procedures may require the use of specialized 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. There- fore, 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. chodina@live.co.uk chodina@live.co.uk

RULES FOR SAFE OPERATION DIMENSIONS AND FEATURES 4-CYCLE ENGINE THEORY SECTION 1: GENERAL INFORMATION SECTION 2: IGNITION SECTION 3: CARBURETION SECTION 4: GOVERNOR CONTROLS AND GOVERNOR SECTION 5: CYLINDER HEAD AND VALVES 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 1 TABLE OF CONTENTS A WORD ABOUT SPECIAL TOOLS Many of the procedures depicted in this manual require the use of special tools. Some of the tools required are available as Generac parts and are listed as such in this manual. ATTENTION! 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. Use of these engines in such applications could result in property damage, serious injury (including paralysis), or even death. chodina@live.co.uk chodina@live.co.uk

If you do not understand any portion of this manual, con- tact Generac or your nearest Generac Authorized Service Dealer for starting, operating and servicing procedures. Throughout this publication and on tags and decals affixed to the engine, DANGER, WARNING and CAUTION blocks are used to alert you to special instruction about a particu- lar operation that may be hazardous if performed incorrectly or carelessly. Observe them carefully. These safety warnings cannot eliminate the hazards that they indicate. Strict compliance with the special instructions while performing the service plus “common sense” are major measures to prevent accidents. The following definitions apply to DANGER, WARNING, CAUTION and NOTE blocks found throughout the manual. These safety symbols indicate the following: DANGER: After this heading you can read handling, installing, operating or servicing instructions that, if not strictly complied with, will result in personal injury. WARNING: After this heading you can read handling, installing, operating or servicing instructions that, if not strictly complied with, may result in personal injury. CAUTION: After this heading you can read instructions for handling, installing, operating or servicing the engine that, if not strictly complied with, may result in damage to equipment and/or property. NOTE: After this heading you can read explanatory statements that require special emphasis. These symbols indicate the following: Points out important safety information that, if not followed, could endanger personal safety and/or property of yourself and others.  Potential explosion hazard.  Potential fire hazard.  Potential electrical shock hazard. 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 oper- ated and maintained. Many accidents are caused by failing to follow simple and fundamental rules or precautions. Generac cannot possibly anticipate every possible circum- stance 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 you use a procedure, work method or operating technique Generac does not specifically recommend, you must satisfy yourself that it is safe for you and others. You must also make sure the procedure, work method or operating technique that you choose does not render the engine to be unsafe. DANGER: Do not tamper with the engine gov- erned 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 EXPLO- SIVE. 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. • Add gasoline 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. • Allow at least two (2) feet of clearance on all sides of the engine, even while operating it outdoors, or you could damage the engine. • 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. 2 RULES FOR SAFE OPERATION chodina@live.co.uk chodina@live.co.uk

3 RULES FOR SAFE OPERATION • 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 • 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. • 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. Use of these engines in such applications could result in property damage, serious injury (including paralysis), or even death. • Engine exhaust gases contain DEADLY carbon monoxide gas. This dangerous gas, if breathed in sufficient concen- trations, can cause unconsciousness or even death. Operate this equipment only in the open air where adequate venti- lation is available. • Do not insert any object through the cooling slots of the engine. You could damage the equipment or injure yourself. • 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 over- heats, 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. 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, al wa ys suppl y the complete model n umber and serial n umber 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. The engine exhaust from this product contains chemicals known to the State of California to cause cancer, birth defects, or other repro- ductive harm. WARNING: chodina@live.co.uk chodina@live.co.uk

4 DIMENSIONS AND FEATURES chodina@live.co.uk chodina@live.co.uk

8 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. B COMPRESSION As the piston reaches bottom dead center (BDC), both the intake and exhaust valves are closed. The piston moves upward toward TDC and the fuel-air mixture is compressed. Just before the piston reaches TDC, ignition occurs. C IGNITION AND POWER By the time the piston reaches TDC , combustion is already in progress. The intake and exhaust valves remain closed as the expanding gases of combustion force the piston downward. 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. chodina@live.co.uk chodina@live.co.uk

Generac GTV990/760 V-Twin OHVI Engine Workshop Service Repair Manual

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