ONAN EngineS BG Parts and Service Manual

Service and Parts Manual BG Engine 965-0251 1 1 A75 Printed In USA

Safety Precautions * It is recommendedthat you read your engine manual and become thoroughly acquainted with your equipment before you start the engine. 1 - 1 This symbol is used throughout this manual to warn of possible serious personal injury. - 1 This symbol refers to possible equipment damage. Fuels, electricalequipment, batteries, exhaustgases andmov- ing parts presentpotentialhazardsthat could resultin serious, personalinjury. Take careinfollowing these recommended procedures. Safety Codes 0 All local,state andfederal codes shouldbeconsultedand compliedwith. 0 This engine is not designedor intendedfor usein aircraft. Any such use is at the owner’s sole risk. General Provideappropriatefire extinguishers and install them in convenient locations. Use an extinguisher rated ABC by NFPA. Makesure that allfastenersonthe engineare secureand accurately torqued. Keep guards in position over fans, driving belts, etc. If it is necessary to makeadjustmentswhile the engine is running, useextreme cautionwhen closeto hot exhausts, moving parts, etc. Protect Against Moving Parts 0 Do not wear looseclothing in the vicinity of moving parts, such as PTO shafts, flywheels, blowers, couplings, fans, belts, etc. 0 Keep your hands away from moving parts. Batteries 0 Before starting work on the engine, disconnect batteries to prevent inadvertentstartingof the engine. 0 DO NOT SMOKE while servicing batteries. Lead acid batteries give off a highly explosive hydrogen gas which can be ignitedby flame, electricalarcing or by smoking. 0 Verify battery polarity before connecting battery cables. Connect negative cable last. Fuel System 0 DO NOTfillfuel tanks while engine is running. DO NOTsmokeor use an openflame inthe vicinity of the engine or fuel tank. Internalcombustionengine fuels are highly flammable. Fuel lines must be of steel piping, adequately secured, and free from leaks. Piping at the engine should be ap- provedflexible line. Do not use copper pipingfor flexible lines as copper will work harden and become brittle enough to break. Be sure all fuel supplies have a positiveshutoff valve. Exhaust System Exhaustproducts of any internalcombustionengine are toxic and can cause injury, or death if inhaled. All engine applications, especially those within a confined area, should be equipped with an exhaustsystem to discharge gases to the outside atmosphere. 0 DO NOT use exhaust gases to heat a compartment. 0 Makesure that your exhaust system is free of leaks. En- sure that exhaust manifolds are secure and are not warped by bolts unevenlytorqued. Exhaust Gas Is Deadly! Exhaustgasescontaincarbon monoxide,a poisonousgasthat mightcause unconsciousness anddeath. It is an odorless and colorless gas formed during combustion of hydrocarbonfuels. Symptoms of carbon monoxide poisoning are: 0 Dizziness 0 Vomiting 0 Headache 0 MuscularTwitching 0 Weakness and Sleepiness If you experience any of these symptoms, get out intofresh air immediately, shut downthe unitand do not useuntil it has been inspected. The best protection against carbon monoxide inhalation is proper installation andregular, frequent inspections of the complete exhaustsystem. If you noticea change inthe sound or ap- pearance of exhaust system, shut the unit down immediately andhave it inspectedand repairedat once by a competent mechanic. Cooling System Throbbing in Temples 0 Coolantsunder pressure have a higher boilingpoint than water. DO NOT open a radiator pressure cap when cool- ant temperature is above 212 degrees F (1 00 degrees C) or while engine is running. 0 Makesure that oily rags are not left on or nearthe engine. 0 Remove all unnecessarygreaseand oilfromthe unit. Ac- cumulated grease and oil can cause overheating and subsequent engine damage and present a potential fire hazard. 4 Keep The Unit And Surrounding Area Clean c

TABLE.OF CONTENTS . .TITLE PAGE General Information ............................................. 2 Specifications ................................................... 3 Dimensions and Clearances ....................................... 4 Assembly Torques and Special Tools ............................. 4 Engine Troubleshooting ......................................... 5 Oil System ...................................................... 6 Fuel System ...................................................... 8 Ignition and Battery Charging .................................... 12 Starting System ................................................. 17 Engine Disassembly ............................................. 19 Engine Wiring Diagram .......................................... 31 t 1

GENERAL INFORMATION This manual contains proper information for the servicing and overhaul of your Onan engine. Use the PARTS CATALOG in the rear portion of this book to help you with disassemblyand assembly procedures. Flywheel end of engine is considered the front. Left and right sides are determined looking at front of engine. If it is necessary to contact your dealer or the factory about this engine, always supply the complete MODEL and SPEC NUMBER as well as the SERIAL NUMBER shown on the engine nameplate. The engine nameplate is located on left side of blower housing (end opposite oil filter). Refer to the TROUBLESHOOT/NG GUIDE for assistance in locating and correcting troubles which may occur. If a major repair or overhaul becomes necessary, the engine should be carefully checked and necessary repairs made by a competent mechanic. Maintain factory limits and clearances as shown, replacing worn parts when necessary. P ENGINE MODEL REFERENCE Identify your model by referring to the MODEL and SPEC (specification) NO. as shown on the unit nameplate. Always use this number and the engine serial numberwhen making reference toyourengine. How to interpret MODEL and SPEC NO. . Factory code for general identification purposes. Specific Type: S-MANUAL STARTING MS-ELECTRIC STARTING Factory code for optional equipment supplied. Specification (Spec Letter) advances with factory production modification. I WARNING I TO AVOlD POSSIBLE PERSONAL INJURY OR VICE REPRESENTATIVE MUST PERFORM All SE R VICE, EQUIPMENT DAMAGE, AN AUTHORIZED SER- 2

SP ECIF KAT IONS This manual contains SI metric equivalents that follow immediately in parentheses after the U.S. customary units of measure. Engine Manufacturer ..................................................................... Onan Engine Design.. ............................................ Four Cycle, Air-Cooled. Two Cylinder i-lorsepower (3600 rpm) ...................................................................... 78 Displacement (cubic inches) ................................................... 49.8 (816.22 crn ) Bore .......................................................................... 3-114 (82.55 mm] Stroke ............................................................................ 3 (76.20 mm) Compression Ratio ........................................................................ 7.0:l Crankshaft ........................... .:. ................................ Horizontal. Ductile Iron Valves ..................................................................... Mechanical. Poppet Bearings (Main and Rod) ................................................................ Sleeve Oil Capacity with Filter Change .............................................. 4 Pints (1.89 Iiti-es) 011 Capacity Without Filter Change .......................................... 3.5 Pints (1.66 litresi Battery Charging System .................................... 12 Volt. 15 Amp Flywheel Alternator TUNE-UP SPECIFICATIONS Tappets (Cold) Intake.. ......................................................... -008 (0-29 rnm) Exhaust.. ....................................................... -013 (0.33 mm) Spark Plug Gap ............................................................ .025 inch (0.64 rnm) Ignition Timing (Cold. Static Setting) .................................................... 21'BTC Breaker Point Gap (Full Separation and Engine Cold) ........................ .021 inch (0.53 mm) 3

DIMENSIONS AND CLEARANCES All dimensions and clearances given at room temperature at 7OoF . All values in inches unless otherwise specified . Minimum CAMSHAFT AND CRANKSHAFT Crankshaft Main Bearing Journal to Bearing Clearance ......................... 0.0025 *Crankshaft End Play .......................................................... 0.006 Camshaft Bearing to Camshaft ................................................ 0.0015 Camshaft End Play ........................................................... 0.003 'Crankshaft Rod Journal to Rod Bearing ....................................... 0.0020 Connecting Rod End Play ..................................................... 0.002 Timing Gear Backlash ........................................................ 0.002 01; Pump Gear Backlash ...................................................... 0.002 Piston Pin in Piston ........................................................... 0.0002 Piston Pin in Rod ............................................................. 0.0002 'Piston Ring Gap in Cylinder ................................................... 0.010 Piston Clearance in Cylinder-Measured . 10 Below Oil Control' Ring. 90" from Pin .................................................... 004 Crankshaft Main Bearing Journal-Standard Size ............................... 1.9992 Crankshaft Rod Bearing Journal-Standard Size ............................... 1.6252 PISTON AND CYLINDER Cylinder Bore-Standard Size ................................................. 3.249 TAPPETS AND VALVES "Valve Seat Width ............................................................. 1/32 'Valve Face Angle ........................ .................................... 44" 'Valve Seat Angle ............................................................. 45" Valve Stem to Guide-Intake .................................................. 0.0010 Valve Stem to Guide-Exhaust ................................................ 0.0035 Tappet to Cylinder Block Clearance ........................................... 0.0015 Tappet Adjustment (Cold) 'Intake ...................................................................... 0.007 'Exhaust .................................................................... 0.012 I Maxim u rn 0.0038 0.01 2 0.0030 b 0.0033 0.01 6 0.003 0.005 0.0004 0.0007 0.020 .006 3.250 2.0000 1.6260 1/8 44" 45" 0.0025 0.0040 0.0030 0.009 0.014 * . Frequently used overhaul values . ASSEMBLY TORQUES AND SPECIALTOOLS BOLT TORQUE FT.-LB. Gearcase Cover .......................... 8 . 10 Cylinder Head Bolts (Cold) ............... 14 . 16 Rear Bearing Plate Screws ................ 25 . 27 Starter Mounting Bolts .................... 18 . 20 Connecting Rod Bolt ..................... 14 . 16 Flywheel Cap Screw ...................... 35 . 40 Other 5/16" Cylinder Block Stud and Nuts .......................... 8 . 10 Oil Base ................................. 18 . 23 Manifold Mounting Screws ................ 6 . 10 Oil Pump ................................. 7 . 9 The following special tools are available from Onan . For further information see TOOL CATALOG 900- 00 19 . P Valve Seat Driver Valve Guide Driver Oil Guide and Driver Combination Bearing Remover (Main and Cam) Combination Bearing Driver (Main and Cam) Flywheel Puller 4

ENGINE TROUBLESHOOTING I 5

OIL SYSTEM Do not overfill crankcase. Do not use service DS oil. Do not mix brands norgradesof motor oil. Engine damage could result from mixing non-compatible oils. I CRANKCASE OIL Change crankcase Oil every 50 operating hours and only when engine is warm. (Exception: Drain initial oil fill at 25 operating hours.) To drain, remove the 1/2-inch pipe plug on the rear corner of the oil base. After oil drains, replacethe pipe plug and refill crankcase with 3-1/2 pints (4 pints if changing filter) of a good quality detergent oil. Oil must meet or exceed the API (American Petroleum Institute) designation SEorSEKC. SeeFigures 1 and 2. For temperatures above 30°F, use SAE 30 oil; for temperatures below 3OoF, use 5W30 or 1OW. In extremely dusty conditions or in very cold weather, change oil at least every 25 hours of operation. LWAYS REPLACE IGHTLY OR OIL LEAKAGE MAY OCCUR WARY:NG: 23 Edc'!' REMD'IE O!L CAP NING. O!L WILL @LOW OUT CAUSING POSS BLE INJURY. WH ENGIW iwr+ CAUTION- DO NOT OVERFILL ADD ONE PINT FIGURE 1. CRANKCASE OIL FILL FIGURE 2 OIL DRAlN LOCATION OIL FILTER Change the crankcase oil filter every ?OO hours; change more frequently in extremely dusty conditions. Remove the filter by turning counterclockwise with a filter wrench. Before install- inganewfitter,coatthegasketon thefilterbasewith a light film of new oil. Install.byturning clockwise until a light friction is noted, then turn an additional 1/2 turn. * Crankcase Breather This engine uses a crankcase breather valve for maintaining crankcase vacuum. if the crankcase becomes pressurized as evidenced by oil leaks at the seals, clean baffle pack and valvein asuitablesolvent. See Figure 3. 6

- REED VALVE FIGURE 3. CRANKCASE BREATHER PRESSURE LUBRICATION Pressure lubricated engines use an oil pump to lubricate engine parts. If oil pressure islow,thepump should be checked. To remove the oil pump, it is necessary to detach the intake cup assembly, as illustrated in Figure 4. Check the oil pump thoroughlyfor worn parts. Oil the pump to prime it before reinstalling. Except for gaskets and suction cup, the component parts of the pump are not available individually. Install a new pump assembly if required. b .. . OIL PUMP IN CRANKCASE ON LEFT S UNSCREW OIL PU FROV '?'-l<r -ItP ,T FIGURE 4. OIL PUMP ASSEMBLY If new oil pump gaskets are installed, they should be the same thickness as those removed. A gasket kit with various thickness gaskets is available. OIL BY-PASS VALVE The by-pass valve (located to the right and behind gear cover), controls oil pressure by allowing excess oil to flow directly back to the crankcase. Normally the valve begins to open about 30 psi. The valve is non-adjustable and normally does not need maintenance. To determine if valve is not working correctly,caused by asticky plunger, inspect as follows: 1. Remove the 3/8 x 24 x 1 cap screw located behind 2. Remove spring and plunger with a magnet tool. Clean plunger and spring with a suitable solvent and reinstall. , gear cover and under governor arm. 7

FUEL SYSTEM CARBURETOR CLEANING AND INSPEC- TlON To clean the carburetor, soak all components Check the adjusting needles and nozzle for damage. If float is loaded with fuel or damaged, replace it. The float should fit freely on its pin without binding. the throttle After ;lean Out Carburetor repair and gasket kits are available from your nearest passages with filtered, compressed air. Onan Parts Center. CHOKE FLY I I CHOKE SHAFT AND LEVER AT VALVE NOTE FLOAT AND LEVER ON SOME MODELS ENGINES FUEL PUMP IS MOUNTED DIRECTLY TO CARBURETOR. - SLEEVE ASSEMBLY -dd MA 1% t.gST I N G CARBURETOR BODY 5? IDLE ADJUSTING NEEDLE THROTTLE STOP SCREW THROTTLE SHAFT CARB.URE1 1 \\- FUEL LINE FUEL INLET INLET PLATE ‘FIGURE 5. .EXPLODED VlEW OF CARBURETOR 8

ONAN EngineS BG Parts and Service Manual

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