Generac Power Systems GTH760 Service Manual Download Page 61

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12-1

GeNerAl INForMATIoN

It is recommended that new piston rings be installed when-

ever 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.

Figure 12-1. Remove Rings

Figure 12-2. Remove Piston Pin Locks

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 12-3. 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

material from the end of the ring 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.

SeCTIoN 12: PISToN, rINGS & CoNNeCTING rod INSPeCTIoN & ASSeMblY

Summary of Contents for GTH760

Page 1: ...Generac Power Systems Inc P O Box 297 Whitewater WI 53190 Part No 0F6923 Printed in USA Revision C 08 13 08 ...

Page 2: ... of and advise the service trade of all conceivable procedures or methods by which a service might be per formed 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...

Page 3: ...ications 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 wate...

Page 4: ... operate safely efficiently and reliably only if it is properly operated and maintained Many accidents are caused by fail ing 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 procedu...

Page 5: ...uipment 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 With out 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 sp...

Page 6: ...nter 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 s...

Page 7: ...uel volatility tailored 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 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...

Page 8: ...ghtly 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 for 30 seconds and stop engine Recheck oil level and add if required Restart engine and check for oil leaks DRAIN Figure 1 4 Oil Drain FILTER Figure 1 5 Oil Filter Cleaning Intake Screen Grass particles chaff o...

Page 9: ... 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 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 clean ing Instr...

Page 10: ... 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 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 Check Ignition Engine Running If engin...

Page 11: ... 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...

Page 12: ...uently what appears to be a problem with engine opera tion such as hard starting vibration etc may be the fault of the equipment powered 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 eng...

Page 13: ...lts 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 receptacle in meter 2 Insert BLACK test lead into the COM receptacle in meter 3 Rotate selector to Diode Test position 4 Insert RED test lead clip into connector A Fig...

Page 14: ...ug leads 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 Remove ignition coil screws and lift of ignition coil s See Figure 2 5 Note The flywheel does not need to be removed to service ignition except to check the flywheel key Figure 2 5 Removing Ignition coil Install Ignition coils 1...

Page 15: ...m the 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 Remove flywheel nut and washer Figure 2 8 4 Reinstall flywheel nut Turn nut down flush with top of threads 5 Install flywheel puller 6 Tighten puller screws equally until flywheel loosens Figure 2 9 Figure 2 8 Removing Flywheel Nut Caution Flywheel...

Page 16: ...haft 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 Flywheel And 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 ...

Page 17: ...tical 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 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...

Page 18: ... 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 nuts on the four studs and torque to 5 4 Nm 48 in lbs 4 Connect the fuel line and clamp 5 Using a pliers reassemble the balljoint on the carburetor 6 Connect the breather tube 7 Conn...

Page 19: ...e lever against idle stop screw 11 Adjust 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 speed position adjust the high speed screw to obtain the desired engine speed Do not exceed 4000 RPM Fuel Pump The fuel pump supplied with the engines is a pulse type pump It uses crankcase vacuum pulses drawn from the valve ...

Page 20: ...d on a normal propane cylinder with a tube that is attached to the valve and extends to the bottom of the storage tank Because of pressure in the tank liquid propane is forced 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 elec...

Page 21: ...ricant DO NOT RE USE O RINGS For improving the functional features and lifetime of the sole noid it is recommend that the gaskets and filter be replaced after about two years of operation RESEVOIR BOLT COIL BOLT COIL SPOOL SEALING GASKET SEALING GASKET SEALING GASKET SEALING GASKET Figure 3 12 LPG Solenoid Valve Torque and Lubrication Points NOTE For correct solenoid valve fitting it is essential ...

Page 22: ...rews 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 lif...

Page 23: ...rifice 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 Roc...

Page 24: ...p indenta tion 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 3 23 Figure 3 21 Install Secondary Valve Spring Lever and Pivot Pin Figure 3 22 Make Sure Secondary Lev...

Page 25: ...e 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 17 Install secondary cover and align the cover and diaphragm notches Carefully sta...

Page 26: ...e 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 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 present go ba...

Page 27: ...LP TANKS PRESSURE RELIEF VALVE SOLENOID SHUT OFF ENGINE TO CARBURETOR VAPORIZOR ON DEMAND REGULATOR NOTE ALL FUEL LINES ARE REQUIRED TO BE BRAIDED STAINLESS STEEL COVERED ITEMS INSIDE DASHED LINE ARE OEM SUPPLIED ITEMS OUTSIDE DASHED LINE ARE GENERAC SUPPLIED Figure 3 32 Typical LP Liquid System 3 ...

Page 28: ...3 12 Notes ...

Page 29: ... 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 GEAR ASSEMBLY GOVERNOR SPOOL OIL PASSAGE O RING Figure 4 1 Governor Gear Assembly and Spool 2 Remove any remaining p...

Page 30: ...e The lower bushing is a slip fit and the upper bush ing is pressed in 4 Slide the thrust washer part way onto the new governor arm 5 Insert the governor arm in the lower bushing holder and slide it part way in 6 Install lower e clip on the arm and slide the thrust washer down to it 7 Slip the lower bushing part way on to the arm 8 Slide the arm in until the thrust washer is tight 9 Slide the lowe...

Page 31: ...sition 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 CLINCHING SCREW ID L E W O T Figure 4 5 Static Governor Adjustment GOVERNOR ARM GOVERNOR LEVER CLINCHING BOLT Figure 4 6 Static Governor Adjustment Later Version Figure 4 7 Dynamic Governor Adjustmen...

Page 32: ...d 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 Adjustment Horizontal Shaft 4 4 ...

Page 33: ...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 The valve push rods are aluminum Mark push rods for identification to prevent interchanging 1 2 5 7 6...

Page 34: ...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 com pressor 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 4 Remove Cylinder Head Figure 5 5...

Page 35: ...e guides 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 ...

Page 36: ...ew 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 Figure 5 13 Install Valve Stem Seals 2 Install valves Figure 5 14 Note Lightly coat valve stems with oil or Spectra Lube Red before installing valves Be sure lubricant is not on valve face seat or end of valve stem EXHAUST VALVE INTAKE VALVE Figure 5 ...

Page 37: ...arance 1 Set No 1 cylinder at TDC compression stroke a Adjust rocker arms and check clearance Figure 5 17 Figure 5 17 Adjust Valve Clearances Valve Clearance cold Intake and Exhaust 0 076 mm 003 b Torque jam nut to 19 Nm 168 in lbs 2 Repeat for No 2 cylinder 3 Install valve covers with new gaskets a Torque screws to 6 8 Nm 60 in lbs Reassemble 1 Install cylinder wrappers a Torque M5 screws to 2 8 ...

Page 38: ...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 8 Assemble air cleaner 9 Make Static and Dynamic Governor adjustments as out lined on Page 4 3 1 2 5 7 6 3 4 1 2 3 4 5 6 7 8 8 VALVE COVER LOWER WRAPPER UPPER WRAPPER BLOWER HOUSING OIL COOLER INTAKE MANIFOLD ASSEMBLY ROTATING SCREEN FINGER GUARD Figure 5 18 General Assembly ...

Page 39: ...ators 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 Battery too small 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 starte...

Page 40: ...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 dr...

Page 41: ...inimum pinion speed of 3250 rpm See Figure 6 5 STARTER CONTACTOR STARTER MOTOR TACHOMETER 12 VOLT BATTERY CLAMP ON AMP METER VISE Figure 6 5 Testing Starter Motor Performance Engine oil viscosity too heavy see engine manufacturer s Operators 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 th...

Page 42: ... With ignition switch OFF press starter button If ignition switch and starter 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 ...

Page 43: ...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 44: ...NOID 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 HARNESS PACKARD CONNECTOR 2973422 1 2 3 4 5 WIRE HARNESS PACKARD CONNECTOR 2977048 LEGEND 1 IGNITION KILL TERMINAL YELLOW 2 BATTERY CHARGER RED 3 LOW OIL PRESSURE SWITCH BROWN 4 CARBURETOR FUEL SOLE...

Page 45: ...UEL SHUTOFF SOLENOID 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 TO GROUND IGNITION SUPPLY 12V TO CRANK ENGINE SUPPLY 12V TO ALLOW FUEL FLOW IC SP SUPPLIED BY 30 AMP FUSE CUSTOMER BLACK CONNECT TO IGNITION GROUND WIRE TO GROUND IGNITION ON HIGH...

Page 46: ...NOTES 6 8 ...

Page 47: ...wn 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 20 Amp System 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 chargin...

Page 48: ... 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 Charging System Schematic Note With the engine running the battery voltage should be at least 13 Volts Batteries Note See Section 6 for battery size and cable selection information Figure 7 4 20 Amp Alternator Section 7...

Page 49: ...ure 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 NOTE Some differences may exist between low oil pres sure systems Refer to the electrical schemat...

Page 50: ...ange 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 the oil comp...

Page 51: ... 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 Generac uses two relief valves a Cold Start and a Common valve When the oil is cold and the engine is started the oil p...

Page 52: ...Section 8 Lubrication System 8 4 Figure 8 8 Typical V twin Engine Oil Flow Vertical Shaft Engine Shown ...

Page 53: ... 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 cyl inder 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 interchan...

Page 54: ...t 7 Remove oil pump from crankcase cover Note Clean all surfaces of gasket material Remove oil seals and thoroughly clean components in solvent Organize components keeping parts which are assem blies together Figure 9 5 Remove Oil Pump Vertical Shaft Engine PICK UP SCREEN OIL PUMP Figure 9 6 Remove Oil Pump Horizontal Shaft Engine Section 9 Engine Disassembly 9 2 ...

Page 55: ...h 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 Figure 10 2 Check Cylinder Bore TOP CENTER BOTTOM Figure 10 3 Measure at Six Points Cylinder Finish Cross Hatch It is recommended that the cylinder bores be recondi tioned...

Page 56: ...MPORTANT 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 Honing grit is highly abrasive and wi...

Page 57: ...mm 1 16 below the mounting surface Check Camshaft Bearings Use a telescoping gauge and caliper to check camshaft bear ings If camshaft bearings are worn crankcase or crankcase cover must be replaced For vertical shaft engines the gerotor cover must be replaced See Figure 10 8 TELESCOPING GAUGE Figure 10 8 Checking PTO Side Camshaft Bearing TELESCOPING GAUGE Figure 10 9 Checking Magneto Side Camsha...

Page 58: ...linder Crankcase Cover 10 4 CLAMP THIS END IN VISE MATERIAL WOOD 25 4mm 1 x 216mm 8 5 x 254mm 10 0 Ø12mm 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 Honing Fixture ...

Page 59: ...shaft 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 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 MAGNETO JOURNAL INTAKE LOBES EXHAUST LOBES PTO JOURNAL ...

Page 60: ...Notes ...

Page 61: ... 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 gau...

Page 62: ...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 piston must be on flywheel side 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 en...

Page 63: ...wer oil scraper ring a Install upper oil scraper ring 2 Install center compression ring with chamfer up 3 Install top compression ring Note Top compression ring may be installed with either side up CASTING MARK MUST FACE FLYWHEEL SIDE NUMBER MUST FACE PTO SIDE Figure 12 9 Assemble 2 Rod And Piston TOP COMPRESSION RING EITHER SIDE UP CENTER COMPRESSION RING DIMPLE MUST FACE UP OIL RING EXPANDER AND...

Page 64: ...Notes ...

Page 65: ...ove 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 fly wheel side Figure 13 3 a Push piston down by hand or with the handle of a hammer until connecting rod is seated on crankpin 4 Assemble connecting rod cap to rod with match marks aligned Figure 13 4 a Torque screws to 24 4 Nm ...

Page 66: ...igure 13 5 Installing Camshaft OIL PASSAGE O RING Figure 13 6 Crankcase Oil Passage O ring INSTALL Oil Pump 1 Lubricate gerotor and set in place 2 Install oil pump cover 3 Torque screws to 12 2 Nm 108 in lbs See Figure 13 7 Figure 13 7 Installing Oil Pump INSTALL Crankcase cover Lubricate PTO seal and cam gear bearing 1 Rotate governor shaft so that the paddle rests against the oil pump pick up Fi...

Page 67: ...d Push coil as far back as possible and tighten one screw to hold coil in place 5 Repeat for second coil Note The side shown in Figure 13 11 must face up on both coils or the engine will not function properly 6 Install ground wire onto tab terminal on ignition coils Important Make sure wires are routed over coil mount ing posts and under breather tube GROUND WIRE ROUTING Figure 13 11 Install Coils...

Page 68: ...L 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 Insert push rods into recess in tappets A B C D E F TORQUE SEQUENCE FOR HEADS C A B D Figure 13 14 Install Cylinder Head Install Rocker Arms 1 Lubricate rocker arms and ball studs with clean engine oil 2 Assemble b...

Page 69: ...rms and check clearance Figure 13 16 Valve Clearance cold INTAKE and EXHAUST 0 076mm 003 b Torque ball studs and 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 Figure 13 16 Adjust Valve Clearance VALVE COVER GASKET Figure 13 17 Install Valve Covers and Gaskets General Assembly 1 Install cylinder shield...

Page 70: ...reen 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 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 10 Connect governor linkage and speed control linkage refer to Section 4 11 Install spa...

Page 71: ...wheel 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 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 Common Specifications Ignitio...

Page 72: ...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 19 959 19 98 mm 7858 7866 19 93 mm 784 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 39 06 39 07 mm 1 5378 1 5382 39 09 mm 1 539 Piston Pin Beari...

Page 73: ...Notes ...

Page 74: ...Notes ...

Page 75: ......

Page 76: ...Generac Power Systems Inc P O Box 297 Whitewater WI 53190 Part No 0F6923 Printed in USA Revision C 08 13 08 ...

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