Generac Power Systems GTH1000 Service Manual Download Page 74

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Generac Power Systems, Inc.

S45 W29290 Hwy. 59

Waukesha, WI 53189

1-888-GENERAC

(1-888-436-3722)

generac.com

Part No. 0F6923 Printed in USA Rev. D 10/24/12

Specifications are subject to change without notice

No reproduction allowed in any form without prior written consent from Generac Power Systems, Inc.

Summary of Contents for GTH1000

Page 1: ...ENGINE SERVICE MANUAL A I R C O O L E D E N G I N E S OHVI V Twin Engine MODELS GTH760 990 1000 GTV760 990 1000...

Page 2: ...f and advise the service trade of all conceivable procedures or methods by which a service might be performed nor of any pos sible hazards and or results of each procedure or method We have not undert...

Page 3: ...PISTON RINGS AND CONNECTING ROD INSPECTION AND ASSEMBLY SECTION 13 ENGINE ASSEMBLY SECTION 14 SPECIFICATIONS 1 TABLE OF CONTENTS ATTENTION Generac Power Systems does not approve or authorize the use...

Page 4: ...the engine The engine can operate safely effi ciently and reliably only if it is properly operated and maintained Many accidents are caused by failing to follow simple and funda mental rules or precau...

Page 5: ...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...

Page 6: ...r 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 C IGNITION AND POWE...

Page 7: ...ailored for the season in which the engine will be operated LUBRICATION Oil has four purposes It cools cleans seals and lubricates During normal operation small particles of metal from the cylinder wa...

Page 8: ...ilter 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 farther Figure 1 5 Start and run engine at idle fo...

Page 9: ...ar 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 movi...

Page 10: ...l 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 CHECK IGNITION If spark does not occur look for Shorted ignitio...

Page 11: ...RESSION 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 o...

Page 12: ...at 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 pro...

Page 13: ...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 receptacle in mete...

Page 14: ...ith 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 Note The flywheel doe...

Page 15: ...flywheel see Figure 2 9 FLYWHEEL REMOVE FLYWHEEL 1 Remove two screws that attach fan and fan retainer to flywheel 2 Remove fan retainer and fan 3 Loosen flywheel nut until it is flush with end of cran...

Page 16: ...d crankshaft taper removing all oil dirt or grease 1 Insert flywheel key into crankshaft 2 Align keyways and assemble flywheel to crankshaft Figure 2 11 Torquing Flywheel Nut Figure 2 12 Installing Fl...

Page 17: ...3 2 Vertical Shaft Carburetor 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 t...

Page 18: ...off 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...

Page 19: ...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 13 With the speed control in the high spe...

Page 20: ...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...

Page 21: ...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 filte...

Page 22: ...ws 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 w...

Page 23: ...ifice 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 regulato...

Page 24: ...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...

Page 25: ...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...

Page 26: ...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 b Connect LP line s reconnect batte...

Page 27: ...bricate all moving parts when reassembling GOVERNOR REMOVAL AND INSTALLATION 1 Leverage gear assembly and governor spool off of governor shaft GOVERNOR GEAR ASSEMBLY GOVERNOR SPOOL OIL PASSAGE O RING...

Page 28: ...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...

Page 29: ...osition 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 CLINCHING SCREW ID L E W O T...

Page 30: ...GOVERNOR Figure 4 8 Dynamic Governor Adjustment Vertical Shaft SPEED CONTROL LEVER ALLEN WRENCH Figure 4 9 Dynamic Governor Adjustment Horizontal Shaft HIGH SPEED SCREW Figure 4 10 Dynamic Governor A...

Page 31: ...ove 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...

Page 32: ...hort 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 Remo...

Page 33: ...e 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...

Page 34: ...13 b Lubricate inner top lip of valve stem seal with oil Figure 5 13 Install Valve Stem Seals 2 Install valves Figure 5 14 Note Lightly coat valve stems with oil before installing valves Be sure lubri...

Page 35: ...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 Figure 5 17 Adjust Valve Clearances 2 Set No 2 cyl...

Page 36: ...Nm 40 in lbs b If engine is equipped with finger screws tighten screws by hand to approximately 1 3 Nm 12 in lbs 8 Assemble air cleaner 9 Make Static and Dynamic Governor adjustments as outlined on P...

Page 37: ...ors e Dirty or worn starter 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 Ba...

Page 38: ...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...

Page 39: ...Manual STARTER CONTACTOR STARTER MOTOR TACHOMETER 12 VOLT BATTERY CLAMP ON AMP METER VISE Figure 6 5 Testing Starter Motor Performance Some equipment manufacturers may use a constant drive pump which...

Page 40: ...itch 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...

Page 41: ...6 5 SECTION 6 ELECTRIC STARTER 6 FEMALE PACKARD CONNECTOR FUSE Figure 6 8 Vertical Shaft Figure 6 9 FEMALE PACKARD CONNECTOR FUSE Figure 6 10 Horizontal Shaft Figure 6 11...

Page 42: ...OID WHITE 4 LOW OIL PRESSURE SWITCH BROWN 5 OPEN 1 2 3 4 5 LEGEND 1 LOW OIL PRESSURE SWITCH BROWN 2 IGNITION KILL TERMINAL YELLOW 3 OPEN 4 CARBURETOR FUEL SOLENOID WHITE 5 STARTER SOLENIOD ORANGE WIRE...

Page 43: ...IL PRESSURE SP SPARK PLUG SM STARTER MOTOR IC IGNITION COIL SUPPLIED BY CUSTOMER WHITE WHITE AC OUTPUT AC OUTPUT DC OUTPUT FS FS FUEL SHUTOFF SOLENOID CONNECT TO IGNITION GROUND WIRE TO GROUND IGNITIO...

Page 44: ...NOTES 6 8...

Page 45: ...wires as shown in Figure 7 1 Meter test clip leads may be attached to either AC output terminal 5 With the engine running at 3600 RPM output should be no less than 26 Volts AC 6 If no or low output i...

Page 46: ...g is greater than when the engine is stopped the charging system is working CHARGING SYSTEM REGULATOR VOLTAGE BATTERY STATOR SUPPLIED BY B STARTER STUD CUSTOMER WHITE WHITE AC AC B Figure 7 3 Basic Ch...

Page 47: ...ote 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 sta...

Page 48: ...ilter 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 e...

Page 49: ...e lubrication system see Figure 8 6 PRESSURE RELIEF VALVES When a constant displacement pump is used a relief valve is neces sary to relieve the build up of pressure in the system Relief valves are ne...

Page 50: ...LIEF VALVE 60 psi COMMON PRESSURE RELIEF VALVE 40 psi CAP RELIEF BALL RELIEF SPRING The components of both pressure relief valves are identical The difference in pressure is determined by the depth of...

Page 51: ...re 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 preve...

Page 52: ...over sump Figure 9 4 Remove Crankshaft Note Clean all surfaces of gasket material Remove oil seals and thoroughly clean components in solvent Organize components keeping parts which are assemblies tog...

Page 53: ...tch 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...

Page 54: ...mportant that the entire cylinder and crankcase be thor oughly cleaned after honing First wash the cylinder and crankcase carefully in a commercial solvent or kerosene Then thoroughly wash cylinder an...

Page 55: ...oil seal and press it in until it is 1 5mm 1 16 below the mounting surface CHECK CAMSHAFT BEARINGS Use a telescoping gauge and caliper to check camshaft bearings If camshaft bearings are worn crankca...

Page 56: ...LINDER CRANKCASE COVER 10 4 CLAMP THIS END IN VISE MATERIAL WOOD 25 4mm 1 x 216mm 8 5 x 254mm 10 0 12mm 0 473 TYP 17mm 0 67 16 5mm 0 65 183 5mm 7 224 10 5mm 0 413 216mm 8 504 254mm 10 0 Figure 10 10 H...

Page 57: ...aft reject sizes in Section 14 FLYWHEEL KEY OIL GALLERY OIL GALLERIES CRANKPIN PTO JOURNAL MAGNETO JOURNAL TIMING GEAR Figure 11 1 Check Crankshaft CHECK CAMSHAFT Inspect gear teeth lobes and journals...

Page 58: ...NOTES...

Page 59: ...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 show...

Page 60: ...PISTON PIN BEARING Figure 12 7 Check Rod Bearings ASSEMBLE PISTON AND CONNECTING ROD Lubricate parts with engine oil and assemble 1 piston and connect ing rod Figure 12 8 1 Notch or casting mark on t...

Page 61: ...er a Install lower oil scraper ring a Install upper oil scraper ring 2 Install center compression ring with dimple up 3 Install top compression ring with dimple up CASTING MARK MUST FACE FLYWHEEL SIDE...

Page 62: ...NOTES...

Page 63: ...ve 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...

Page 64: ...SAGE O RING 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...

Page 65: ...ew 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 Important Make sure wires are routed over coil m...

Page 66: ...d coil INSTALL CYLINDER HEADS 1 Install cylinder head with new gasket 2 Lubricate threads of head bolts with one drop of oil a Torque head bolts in sequence shown Figure 13 14 to 29 9 Nm 22 ft lbs 3 I...

Page 67: ...rance 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 Fig...

Page 68: ...n 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...

Page 69: ...s 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 Cove...

Page 70: ...9 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...

Page 71: ...NOTES...

Page 72: ...NOTES...

Page 73: ......

Page 74: ...C 1 888 436 3722 generac com 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...

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