Onan T260G Page 1 Service Manual Download

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ONAN T260G ENGINE SERVICE MANUAL

Table of Contents – Page 1 of 2

SAFETY PRECAUTIONS

GENERAL

PROTECT AGAINST MOVING PARTS

BATTERIES

FUEL SYSTEM

EXHAUST SYSTEM

EXHAUST GAS IS DEADLY!

COOLING SYSTEM

KEEP THE UNIT AND SURROUNDING AREA CLEAN

INTRODUCTION

EXHAUST GAS IS DEADLY!

GENERAL INFORMATION

INTRODUCTION

ENGINE MODEL REFERENCE

SPECIFICATIONS

DIMENSIONS AND CLEARANCES

ASSEMBLY TORQUES

ENGINE TROUBLESHOOTING

OIL SYSTEM

FUEL SYSTEM

PULSATING-DIAPHRAGM FUEL PUMP

AIR CLEANER

DASHPOT ADJUSTMENT

GOVERNOR ADJUSTMENT

IGNITION AND BATTERY CHARGING

BREAKER POINT IGNITION SYSTEM

IGNITION TIMING

ELECTRONIC IGNITION SYSTEM

IGNITION TIMING

BREAKER POINT AND ELECTRONIC IGNITION COILS

SPARK PLUGS

BATTERY INSPECTION

BATTERY JUMP STARTING

FLYWHEEL ALTERNATOR

ALTERNATOR OUTPUT TEST

STARTING SYSTEM

ELECTRIC STARTER

Summary of Contents for T260G

Page 1: ...AND CLEARANCES ASSEMBLY TORQUES ENGINE TROUBLESHOOTING OIL SYSTEM CRANKCASE OIL OIL FILTER CHANGE CRANKCASE BREATHER PRESSURE LUBRICATION FUEL SYSTEM CARBURETOR CARBURETOR OVERHAUL PULSATING DIAPHRAGM FUEL PUMP AIR CLEANER DASHPOT ADJUSTMENT GOVERNOR ADJUSTMENT IGNITION AND BATTERY CHARGING BREAKER POINT IGNITION SYSTEM IGNITION TIMING ELECTRONIC IGNITION SYSTEM IGNITION TIMING BREAKER POINT AND E...

Page 2: ...NDING FLYWHEEL GEAR COVER GOVERNOR CUP TIMING GEARS PISTONS AND CONNECTING RODS CYLINDER BLOCK CRANKSHAFT BEARINGS CRANKSHAFT ENDPLAY CHECKING CONNECTING ROD BEARING CLEARANCE OIL SEALS PISTON ASSEMBLY INSTALLATION OF PISTON IN CYLINDER CYLINDER HEADS CYLINDER HEAD STUD TEST AND REPLACEMENT PROCEDURE ALIGNING BLOWER WHEEL VENTURI AND CHAFF SCREEN ...

Page 3: ...Service Manual Engine ...

Page 4: ...unning DO NOT smoke or use an open flame in the vicinity of the engine or fueltank Internal combustion enginefuels are highly flammable Fuel lines must be of steel piping adequatelysecured and free from leaks Pipingat the engineshouldbe approvedflexible line Donotusecopper piping for flexible lines as copper will work harden and become brittle enough to break Be sure all fuel supplies have a posit...

Page 5: ...sgas Carbonmonoxide is poisonous and can cause unconsciousness and death Symptoms of carbon monoxide poisoning can include Dizziness Throbbingin Temples Nausea Muscular Twitching Headache Vomiting Weakness and Sleepiness Inability to Think Coherently IF YOUOR ANYONE ELSE EXPERIENCE ANYOF THESE SYMPTOMS GET OUT INTOTHEFRESHAIRIMMEDIATELY If symptoms persist seek medical attention Shut down the unit...

Page 6: ...he wiring diagram on the last page of the manual shows howtheelectricalcomponents are inter connected A parts catalog availableat the dealer level contains detailed exploded views of each assembly and the individual piece part numbers and their proper names for orderingreplacement parts Useonly Genuine Onan replacement parts to ensure qualityandthe best possible repair and overhaul results When or...

Page 7: ... 1 Rated Speed Maximum RPM 3600 Power at BHP 24 Rated Speed k w 1 7 9 Oil Filter Full Flow Oil Capacity Without Qt 2 5 Filter 2 4 Oil Capacity Qt 3 0 Filter Change litre 2 8 Crankshaft Rotation viewed from flywheel lockwise Governor ble Speed Mechanical Valve Clearance Cold Intake in 005 mm 0 1 3 Exhaust in 013 Spark Plug in 025 0 64 Breaker PointGap Static Spec A E in 020 Full Separation and Engi...

Page 8: ...7 BeginSpec F 0 0024 0 061 0 0042 0 107 Connecting Rod Journal Diameter 1 6252 41 28 1 6260 41 30 Crankshaft End Play 0 005 0 13 0 009 0 23 and rod bolts properly torqued 1 7505 44 46 1 7510 44 48 Connecting Rod SideClearance 0 0020 0 051 0 0160 0 406 Piston Pin Bushing Bore Without bearing 0 8115 20 61 0 8125 20 64 Finished bore 0 7504 19 06 0 7508 19 07 AluminumRod 0 0020 0 051 0 0033 0 084 Iron...

Page 9: ...rancein Bore VALVE SPRINGS INTAKEAND EXHAUST Valve Spring Free Length Approx Valve Spring Length Valve Open Valve Closed Spring Load 1 375inch Valve Closed Spring Load 1 125inch Valve Open MINIMUM MAXIMUM Inches mm Inches mm 0 0070 0 1 78 0 0090 0 229 0 7502 19 055 0 7506 19 065 0 080 2 032 0 081 2 057 0 080 2 032 0 081 2 057 0 188 4 775 0 189 4 801 0 0001 0 003 0 0005 0 01 3 0 0002 0 005 0 0008 0...

Page 10: ...mm GEAR BACKLASH Timing Gear Spec A E BeginSpec F spec A E BeginSpec F Oil Pump Gear GOVERNOR Dashpot to Governor ArmBracket 0 002 0 051 0 003 0 076 0 001 0 025 0 005 0 127 0 002 0 051 0 005 0 127 0 001 0 025 0 008 0 203 0 040 1 02 0 060 1 52 3 3 ...

Page 11: ...Rod Bolt SpecA E Begin Spec F Flywheel Capscrew Starting Mounting Bracket to Oil Base Screws Begin Spec F TABLE 1 TORQUE SPECIFICATION DESCRIPTION F1 Lb Nm Gear CaseCover Oil Pump 14 Valve Cover Exhaust Manifold Mounting 11 13 15 18 Intake Manifold Mounting 19 Screws 14 16 19 22 Screws 17 25 28 34 38 Begin Spec F Other 1 4 4 Cylinder Block Studs 23 Spec A E 14 16 1 9 22 and Nuts 27 29 37 39 Other ...

Page 12: ...Engine Troubleshooting I IGNITIONSYSTEM FUEL SYSTEM INTERNAL ENGINE COOLING SYSTEM AIR COOLED THROTTLE AND GOVERNOR M 1686 1 5 1 ...

Page 13: ... consumption Crankcase pressure can blow out hot oil and cause serious burns Do NOT WARNING check oil while the engine is operating Hot crankcase oil can cause burns if it is spilled or splashed on skin Keep fingers and hands clear when removing the oil drain plug and wear protective clothing ALWAYS REPLACE LEAKAGE MAY OCCUR TIGHTLY OR OIL FIGURE 1 CRANKCASE OIL FILL CAUTIONDo not overfill crankca...

Page 14: ...CAP AND VALVE HOSE CLAMP FIGURE 3 CRANKCASE BREATHER Clean or replacecrankcase breatherbaffleperiodically Besurebafflematerial doesn t comeapartandwork into the manifold To disassemble remove breather hose from cap and valve assembly Remove cap and valve assembly and wash in a suitablesolvent Replace cap andvalveifballs do not move freely Pull baffle out and washin solvent To allow free operation ...

Page 15: ...e The by passvalve located to the right and behind gear cover Figure 5 controlsoilpressurebyallowing excess oil to flow directly backtothe crankcase Normallythevalvebeginstoopenabout 20 psi 138 kPa The valve is non adjustable and normally does not need maintenance Determine if valve is operating normally by inspecting plunger action as follows 1 Remove the 3 8 x 24 x 7 8 capscrewlocated behind gea...

Page 16: ...ADJUSTMENT IDLE FUEL FS 1002 2 Startthe engine and allow it to warm upthoroughly at least10 minutes Someequipmentmanufacturersmay requirehigher throttle stop speed and governor low speed rpm settings Refer to equipmentmanufacturer sOpera tor s Manualfor the correct rpmsettings When rpm settings are not specified by theequipment manu facturer use the rpmsettingslisted inSteps 3 and 5 3 Movethe engi...

Page 17: ...ssembly a thorough cleaning and replacement of worn parts Carburetorrepair parts are available General instructions for overhauling a carburetor are given below Carefully note the position of all parts whileremoving to assure correct placement when reassembling Readthrough all the instructions before beginningforabetterunderstanding of thepro cedures involved Carburetor components areshown in Figu...

Page 18: ... 02 0 02 INCH TANG HERE 0 51 0 51 mm TO ADJUST FLOAT LEVEL ADJUSTMENT 0512 028 FLOAT LEVEL ADJUSTMENT 1 Soak all metal componentsnotreplaced in car buretor cleaner Do not soak non metal floats or other non metal parts Follow the cleaningmanu facturer s recommendations 2 Cleanallcarbonfrom the carburetor bore especially where thethrottle and choke plates seat Be careful not to plug the idle or main...

Page 19: ... carburetor on its side and measurefloat level Figure4 Adjust float level only if necessary Measure float drop the distance fromthe top of carburetor body to top offloat Adjust only if necessary 3 Position gasket on lower carburetor section and install upper carburetor section 4 Install idle adjustment screw throttle stop screw and fixed main jet plug 5 Mount carburetor on intake manifold and inst...

Page 20: ...es specified in TABLE 1 1 Remove the vacuum and fuel lines Inspect the lines for wear cracking or brittleness Replace as necessary 2 To insure correct alignment when reassembling scribe a line across the outer pump parts on each end of the pump 3 Holdingthe pump carefully remove the assembly screws Figure 5 4 Carefully pull apart thepump sections and check forwornordamaged parts Replacewith new pa...

Page 21: ... rings causing excessive blow by DASHPOT ADJUSTMENT On engines equippedwith a dashpot adjust as follows 1 Pull governor arm and linkage awayfrom car buretor until throttle stop contacts throttle stop screw Holding throttle against throttle stop screw adjust dashpot to obtain 0 050 inch 1 27 mm clearance Figure 8 Securedashpotto air cleaner support bracket with hex nut CAUTION I Donot grip dashpot ...

Page 22: ...e9 1 2 3 On Disconnect linkage A fromone of holes C Pushlinkage A and governorarm B asfar back toward carburetor as they will go Holding linkage andgovernor arm toward direc tion of carburetor insertend of linkageinto whichever hole C in governor arm linesup the closest If between two holes insert in next hole out Install clip tosecure rod toarm side pull governor the governor spring is set by the...

Page 23: ... housingto expose timing marks on top of gearcase coverand flywheel Figure 2 FLYWHEEL TIMING TC MARK M 1397 FIGURE 2 TIMING MARKS 6 Adjust point gap by rotating crankshaft clockwise facing flywheel by hand until the points arefully open Setthe point gap using flat feeler gauge at 0 020 inch 0 51 mm by adjusting the socket head screw D inward or outward Figure1 A0 020 inch pointgap isequivalent to ...

Page 24: ...ay from spark plug hole Turn key onand crank engine over for 5 seconds while watching for spark If a spark occurs regularly the problem is not in the ignition system If no spark occurs go to step 3 CAUTION negative terminal Thiswillcause Never putjumper lead to the coil failure of the electronic ignition module 3 Connect a jumperlead directly fromthe positive battery terminal to the positive coil ...

Page 25: ...this point the flywheel timing mark should line up with the proper timing degree see SPEClFlCATlONS mark located on the gearcase timing marks Torecheck timing the flywheel must be rotated another com plete revolution in the clockwise direction Moving the flywheel back and forth across the timing marks will not activate theelectronic ignition control 5 Install spark plugs wires andblower housing BR...

Page 26: ... trouble Make sure battery cablesare in good condition and that contacting surfaces are clean and tightly connected Donotreversebatteryleads Use recommended batterytools when disconnecting leads to avoid mechanical batterydamage can causeseverepersonalinjury Do Ignition of explosivebatterygases not smoke while servicing batteries GRAVITY READING SPECIFIC SHOULDBE 1 260 at 77 F 25 C FIGURE 7 SPECIF...

Page 27: ...y 2 3 4 5 6 Theregulator rectifierhasbuilt inprotectionagainst opencircuitsorshortcircuitsonthe alternator output B terminal Eithercondition willcause the regulator rectifier to shut off andappear as if it isnot functioning Prior to checkingthe regulator rectifier check all wiring between theregulator rectifier B terminaland thebattery positive terminalto assure it isfree of open circuits resistan...

Page 28: ...nectohmmeter testleads towirescoming fromstator Refer to Table 1for resistance specifications If resistance is not as specified replace stator If stator resistance readings areas specified andwindings arenot shorted to ground low AC voltage may be due to loss of magnetism If so blower wheelassembly 2 Examine all wires for loose corroded broken must be replaced Check for magnetism with steel connec...

Page 29: ...8 7 ...

Page 30: ...ENGINE WIRING DIAGRAM Solenoid Shift Type Starter 8 8 ...

Page 31: ...er checking these variables startercontinuesto crank slowly starter must be removed and repaired Starter Removal Starter Disassembly Inertia Type Remove through boltsand separateend cap housing and armature Figure 1 2 Disassembledrive assembly anddrive end cap by loosening the self locking stop nut 3 Inspectstarter for damagedor worn parts 4 Repairor replace all damaged or worn parts as needed Sta...

Page 32: ... Applyagenerous film of silicone base grease GE Versilube 322 L to the shaft threads 4 Remove rear bracket and frame assembly 6 Torque stop nutto a value of 20to 25 ft lbs 27 to 34 Nm 5 Carefully remove armature and lever from front bracket Notedirection of lever and retainer 7 Torque through boltsto a value Of 4 5to 6 ft lbs 6to 8 Nm 6 Remove the two brush mounting screws and remove the rear brac...

Page 33: ... STOPPER 4 Lubrication When starter motor isassembled apply grease to each of thefollowingpoints Recom mended grade Multemp PS No 2 Armature shaft spline Both bushings Both ends of armature Stopper on armature shaft Piniongear Sliding portion of lever 5 Fit overrunning clutch into lever and install with armature in the front bracket 6 Install leverretainer and spacer Position frame assembly over a...

Page 34: ...NT Inspection and Testing Inspect the starter components formechanicaldefects beforetesting for grounds orshorts TestingArmaturetor Grounds Touch armature shaft or core and the end of each commutator barwith a pair of ohmmeterleads Figure 6 A low ohmmeter reading indicates a grounded armature Replace grounded armature ES 1001 FIGURE 6 TESTINGARMATUREFORGROUNDS Inspecting tor an OpenCircuit in Arma...

Page 35: ...eck for shorts between positive sideof brush holder and brush holder base If there is continuity replace holder assembly Check for free movement of brushes All brushes should move freelyin the brush holders Overrunning Clutch Inspectpinion and splineteeth for wear or damage If pinion gear is worn or damaged inspectflywheel ring gear also Rotatepinion Itshouldturn free when turned in one direction ...

Page 36: ...he amount of free travel lash between the pinion gear teeth and the ring gear teeth See Figure 12 If lash is too tight causing binding and slow starter operation or if lash isgreater than 0 035 inch 0 889 mm lash must be adjusted 9 6 FLYWHEELRINGGEAR STARTER GEAR FREE TRAVEL WHEN 0 020 0 015 inch 0 51 0 38mm ENGAGED WITH FLYWHEEL GEAR STARTER MOTOR PINION GEAR ES 1003 5 6 7 8 9 FIGURE 12 CHECKINGS...

Page 37: ...llerandring Operation 9 Remove all accessories such as oil filter starter Start engine and checkoil pressure Run for approxi intake manifold fuel lines spark plugs etc mately 15 minutes to bring engine to operating temper 10 Remove breakerpoint box ature Checkfor oil leaks fuel leaks and exhaust leaks 11 Remove oil base oil pump and cylinderheads Adjust carburetor and governor for speed andsensiti...

Page 38: ...d not Figure 1 To correct the valve clearance use a 7 16 inch open end wrench to turn the adjusting screw to obtain the correct clearance The screw is self locking and willstay where it is set A 9 16 inch 14 mm open end wrench is required to hold the tappet while turning the adjusting screw To adjust valves on the righthand cylinder turn engine one complete revolution and again line up mark on the...

Page 39: ...r a seal is providedbehindthe intake valve guides only The smaller diameter of the CAUTION the guide or tappetbores Be careful Driving out old guides can damage not tostrike guide bores with driver or allow guide to strike tappet bores during removal Valve Guide Installation Run a small polishing rod covered with crocus cloth through valve guide holes to clean out carbon andother foreignmaterials ...

Page 40: ...ts theboresmustbemachined for an oversize seat USE NEW VALVE SEAT TO ADJUST PULLER DEPTH PULLER JAWS FIGURE 4 VALVE SEAT REMOVAL C 1104 10 4 Valve Seat Removal Remove carbon and combustion deposits from valveseat Select proper puller size determined by inside diameter of valve seat On some pullers usea new seat as a guide to adjust puller depth Figure 4 Puller jaws must expand into cylinder block ...

Page 41: ...aximum diameter on valve seat seating surface FIGURE 6 VALVE INTERFERENCE ANGLE VT 1021 10 5 Refinish valve facesto a44 angle onavalve refacing machine The first cut from valve face must be a light grinding Check if there is an unevenness of metal being removed If only part of valve s face has been touched check to see if valve is properly seated in machineorif valve is warped worn ordistorted Whe...

Page 42: ...oth side of the governor yoke must rideagainstthe governor cup Turn thegovernor armand shaftclockwise as far as possible and hold in this position until thegear cover is installed flush against the crankcase Be careful not to damage the gear cover oil seal 2 Installa puller bar on the flywheel Figure 8 FLYWHEEL MOUNTING SCREW cs loo0 FIGURE 8 BLOWER WHEEL PULLEY 3 Turn the puller bar bolts in alte...

Page 43: ...d up with the space in the camshaft gear a flyball can slip into the space and cause engine racing and governing problems Figure 10 When installing the governor cup tilt the engine so the gear is up put the flyballs in place Figure lo and install the cup and snapring on thecenter pin The camshaft centerpin extends out3 4inch 19mm from the end of the camshaft This distance providesan in and out tra...

Page 44: ...and rod 5 Mark each piston and rod assembly so they can be returnedtotheir respectivecylinders after overhaul Keep connectingrodbearingcapswith their respective rods 6 Remove the piston rings from the piston with a piston ringspreader Figure 13 Remove the piston pin retainer and push the piston pin out FIGURE 13 REMOVING PISTON RINGS 7 Remove dirt and deposits from the piston surfaces with anappro...

Page 45: ...maintained for satisfactory operation 2 Refer to DIMENSIONS ANDCLEARANCES to determine where to measure piston to be sure the total clearance follows specifications 1 Inspect the pistons for fractures atthe ring lands skirts and pin bosses Check for wear at the ring landsusinga new ringandfeeler gauge Figure 15 Replace the piston when the side clearance of the top compression ring reaches 0 008 in...

Page 46: ...ngine thoroughly inspect block for any condition that wouldmake it unfit for further use This inspection must be madeafter all parts have beenremovedandblockhasbeenthoroughly cleaned and dried 1 Makea thorough check for cracks Minute cracks may be detected by coating the suspected area with a mixture of 25 percent kerosene and 75 percent light motor oil Wipe the part dry and immediately apply a co...

Page 47: ...nd honed to the next oversize A reboringmachineisused when goingto oversize pistons Reboring the Cylinder Rebore and hone engine whenever cylinder bore is worn damaged out of round or if cylinder taper exceeds specifications A worn cylinder bore should be resizedto the smallest standard oversizediameter at which it will clean up The final finish and bore diameters should thenbe obtained by honing ...

Page 48: ...top middle and bottomat 90 degree angles 6 Crosshatch formed by the stones should forman included angle of 23 degrees This can be achieved by moving the rotating hone 250to 450 rpm upanddown in cylinder bore about 40 times per minute 7 Clean cylinder bores thoroughly with soap water andclean rags A clean white rag shouldnot becomesoiled on wall after cleaning is complete Do not use a solvent or ga...

Page 49: ... installation Use a press or a suitable driver to remove bearings Support casting to avoid distortion and to avoid damaging the bearing bore during removal and installation If regrinding of crankshaft Journals is necessary the whichdo not require line reaming or lineboring after work should be doneby a reputable machineshop that installation Clean outside of the bearing and bearing 0 010 0 020 and...

Page 50: ...st washer with lock pins before tightening end plate or lock pins will be damaged Engines shipped from the factory have separate thrust CRANKSHAFT ENDPLAY washers and main bearings for both front and rear of bearing with attached thrust washer as shown in usingthetorquerecommendedin ASSEMBLY TORQUES Figure 22 Do notaddanadditionalthrustwashertothis AND SPECIALTOOLS check thecrankshaft end playas f...

Page 51: ...ndths of an inch FRONT GEAR COVER OF GEAR COVER MOUNTINGFACE THISGEAR COVER SURFACE SHOULD BE CLEANED OF ALL OLD SEALINGCOMPOUND BEFOREINSTALLINGS E A L GEAR COVER OIL SEAL FIGU RE 24 MEASURING BEARING CLEARANCE OIL SEALS The bearing plate must be removed to replace the oil seal Figure 25 Drivethe oil seal out from the inside Beforeinstalling seals fill the space betweenlips with a multi purpose g...

Page 52: ...ston assembly and insideofthecylinder Compresstheringswitha ring compressor Figure27 Position the piston and rod assembly in the cylinder block Notched side of connecting rod must face camshaft rod bolts must be off set toward outside of block 4 Tap the piston downinto the bore with the handle end of a hammer until the connecting rod is seated on the journal Figure 27 Installthe bearing cap on the...

Page 53: ...o slide the gasket over the studs without the cylinder head behind it or the gasket may tear 5 Install a flat washer two compression washers and nut on eachof the top six studs see Figure 28 for correct sequence When properly installed only the outside edges of the compressionwash ers will be in contact with each other Install a flat washer and nut on each of the four bottom studs f COMPRESSION WA...

Page 54: ...OVE LINE FOR SECTION 1 STUD TEST LEFT CYLtNDER RIGHT CYLINDER NUMBERS INDICATE CORRECT TIGHTENING SEQUENCE FOR CYLINDER HEAD NUTS FIGURE 30 CYLINDER HEADS 10 18 HEAT TREATED NUTS COMPRESSION WASHERS HARDENED WASHERS HEAD GASKET 6 LONG STUDS TOP 4 SHORT STUDS BOTTOM TORQUE TOP SIX NUTS TORQUE BOTTOM FOUR TO 12 LB FT COLD NUTS TO 15 LB FT FIGURE 31 CYLINDERHEADSTUDS 3 Replacethe nuts and then test t...

Page 55: ...place the small bushing with the large bushing and lock into place Using a1 2 13 tap carefully formthe threads making sure there are full threads the entire lengthof the hole 9 After all drilling and tapping iscompleted remove the special fixture andrepeat the same operation on theother cylinderif necessary 10 Remove the ridge around all new holes using a flat fileor a 45 chamfertool When usinga c...

Page 56: ...ower wheel if these parts are separated without noting their relative positions The holes will match up if the parts are aligned as shown in Figure 34 THROUGH PART DIAMETER SCREW HOLES ALIGN BLOWER WHEEL SCREW HOLES ALIGN THROUGH PART DIAMETER VENTURI CHAFF SCREEN POSITION PARTS WITH ALIGNED SCREW HOLESAT TOP FIGURE 34 BLOWERWHEEL VENTURIANDCHAFF SCREEN ALIGNMENT 10 20 ...

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