Kubota WG972-E2 Workshop Manual
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Kubota WG972-E2 Workshop Manual

Gasoline, lpg engine
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WORKSHOP MANUAL
GASOLINE,LPG ENGINE
WG972-E2,DF972-E2
KiSC issued 01, 2006 A

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Summary of Contents for Kubota WG972-E2

  • Page 1 WORKSHOP MANUAL GASOLINE,LPG ENGINE WG972-E2,DF972-E2 KiSC issued 01, 2006 A...
  • Page 2 TO THE READER This Workshop Manual has been prepared to provide servicing personnel with information on the mechanism, service and maintenance of KUBOTA Gasoline / LPG Fuel Engine WG972-E2 and DF972-E2. It is divided into three parts, "General", "Mechanism" and "Servicing".
  • Page 3 WG972-E2, DF972-E2, WSM SAFETY INSTRUCTIONS SAFETY INSTRUCTIONS SAFETY FIRST This symbol, the industry’s “Safety Alert Symbol”, is used throughout this manual and on labels on the machine itself to warm of the possibility of personal injury. Read these instructions carefully.
  • Page 4 WG972-E2, DF972-E2, WSM SAFETY INSTRUCTIONS SAFETY STARTING • Do not start the engine by shorting across starter terminals or bypassing the safety start switch. • Do not alter or remove any part of machine safety system. • Before starting the engine, make sure that all shift levers are in neutral positions or in disengaged positions.
  • Page 5 WG972-E2, DF972-E2, WSM SAFETY INSTRUCTIONS VENTILATE WORK AREA • If the engine must be running to do same work, make sure the area is well ventilated. Never run the engine in a closed area. The exhaust gas contains poisonous carbon monoxide.
  • Page 6 ■ To conform with U.S. EPA and CARB SOREs (Small Off Road Engines) emission regulations, the WG972-E2 / DF972-E2 engine must observe below items. 1. INLET AND EXHAUST SYSTEM The WG972-E2 / DF972-E2 engine must use the below air cleaner and inlet pipe, and exhaust back pressure of the muffler must be within the below values. Part Part No.
  • Page 7 WG972-E2, DF972-E2, WSM IMPORTANT ITEMS OF EXHAUST EMISSION REGULATION 4. KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS (DF972-E2) · Commercial Propane gas only. · Equivalent to Propanes H-D-5 of GPA* standards. (vol %) Others 90 % 2.5 % – *GPA means Gas Processors Association (U.S.A.) W1028533 5.
  • Page 8 WG972-E2, DF972-E2, WSM SPECIFICATIONS SPECIFICATIONS Model WG972-E2 DF972-E2 Number of Cylinder Vertical, water cooled, 4-cycle Vertical, water cooled, 4-cycle Dual Fuel (Gasoline / LPG) engine Type Gasoline engine Gasoline fuel LPG fuel Bore × Stroke 74.5 x 73.6 mm (2.93 x 2.90 in.)
  • Page 9 WG972-E2, DF972-E2, WSM SPECIFICATIONS KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS · Commercial Propane gas only. · Equivalent to Propanes H-D-5 of GPA* standards. (vol %) Others 90 % 2.5 % – *GPA means Gas Processors Association (U.S.A.) W1032351 KiSC issued 01, 2006 A...
  • Page 10 WG972-E2, DF972-E2, WSM PERFORMANCE CURVES PERFORMANCE CURVES (1) Brake Horsepower (5) Net Intermittent Torque (8) Net Continuous Brake a : Gasoline Use (2) Engine Speed (6) Net Continuous Torque Horsepower b : LP Gas Use (3) Specific Fuel Consumption (7) Net Intermittent Brake...
  • Page 11 WG972-E2, DF972-E2, WSM DIMENSIONS DIMENSIONS KiSC issued 01, 2006 A...
  • Page 12 WG972-E2, DF972-E2, WSM DIMENSIONS Electronic Governor Model KiSC issued 01, 2006 A...
  • Page 13 WG972-E2, DF972-E2, WSM WIRING DIAGRAM WIRING DIAGRAM Color of Wiring B ..Black BY ..Black / Yellow GW ..Green / White LW..Blue / White R ..Red Y ..Yellow BOr ..Black / Red Br ..Brown Gr..

  • Page 14: Table Of Contents

    GENERAL CONTENTS 1. ENGINE IDENTIFICATION ................G-1 [1] MODEL NAME AND ENGINE SERIAL NUMBER ........ G-1 [2] CYLINDER NUMBER ................G-3 2. GENERAL PRECAUTIONS ................G-4 3. MAINTENANCE CHECK LIST ............... G-5 4. CHECK AND MAINTENANCE ............... G-6 [1] DAILY CHECK POINTS................G-6 [2] CHECK POINTS OF INITIAL 50 HOURS ..........

  • Page 15: Engine Identification

    WG972-E2, DF972-E2, WSM G GENERAL 1. ENGINE IDENTIFICATION [1] MODEL NAME AND ENGINE SERIAL NUMBER When contacting the manufacture, always specify your engine model name and serial number. The engine model and its serial number need to be identified before the engine can be serviced or parts replaced.
  • Page 16 WG972-E2, DF972-E2, WSM G GENERAL • Month of manufacture Engine Serial Number Month 0001 ~ 9999 10000 ~ January A0001 ~ A9999 B0001 ~ February C0001 ~ C9999 D0001 ~ March E0001 ~ E9999 F0001 ~ April G0001 ~ G9999...

  • Page 17: Cylinder Number

    [C] Vaporizer W1025903 [2] CYLINDER NUMBER The cylinder numbers of KUBOTA gasoline / LPG engine are designated as shown in the figure. The sequence of cylinder numbers is given as No.1, No.2 and No.3 starting from the gear case side.

  • Page 18: General Precautions

    Screws, bolts and nuts should be replaced in their original position to prevent reassembly errors. • When special tools are required, use KUBOTA genuine special tools. Special tools which are not frequently used should be made according to the drawings provided.

  • Page 19: Maintenance Check List

    WG972-E2, DF972-E2, WSM G GENERAL 3. MAINTENANCE CHECK LIST To maintain long-lasting and safe engine performance, make it a rule to carry out regular inspections by following the table below. (The schedule applies to an engine in use under normal conditions.)

  • Page 20: Check And Maintenance

    WG972-E2, DF972-E2, WSM G GENERAL 4. CHECK AND MAINTENANCE [1] DAILY CHECK POINTS Checking Engine Oil Level 1. Level the engine. 2. To check the oil level, draw out the dipstick (1), wipe it clean, reinsert it, and draw it out again.
  • Page 21 WG972-E2, DF972-E2, WSM G GENERAL Checking and Replenish Coolant 1. Without recovery tank : Remove the radiator cap (1) and check to see that the coolant level is just below the port. With recovery tank (2) : Check to see that the coolant level lies between FULL (A) and LOW (B).

  • Page 22: Check Points Of Initial 50 Hours

    WG972-E2, DF972-E2, WSM G GENERAL Checking Air Cleaner Element (If necessary) 1. To clean the element, use clean dry compressed air on the inside of the element. Air pressure at the nozzle must be under 205 kPa (2.1 kgf/cm 30 psi).

  • Page 23: Check Points Of Every 50 Hours

    WG972-E2, DF972-E2, WSM G GENERAL Replacing Oil Filter Cartridge CAUTION • Be sure to stop the engine before changing filter cartridge. 1. Remove the oil filter cartridge (1) with the filter wrench. 2. Apply a slight coart of oil onto the new cartridge gasket.

  • Page 24: Check Points Of Every 100 Hours

    WG972-E2, DF972-E2, WSM G GENERAL Checking Fuel Leakage (LPG Fuel Line) (DF972-E2) ■ IMPORTANT • Never test for gas leaks with a FLAME. ■ NOTE • Check for fuel leakage by using soapy water or gas-detector, if leakage is found, correct leakage.
  • Page 25 WG972-E2, DF972-E2, WSM G GENERAL Checking and Cleaning Fuel Filter (Gasoline Line) 1. Check the fuel filter. 2. If the fuel filter is dirty, clean it or replace it. CAUTION • Stop the engine when attempting to check and clean the fuel filter.

  • Page 26: Check Points Of Every 200 Hours

    WG972-E2, DF972-E2, WSM G GENERAL [5] CHECK POINTS OF EVERY 200 HOURS Changing Engine Oil CAUTION • Be sure to stop engine before changing engine oil. 1. Start and warm up the engine for approx. 5 minutes. 2. Place an oil pan underneath the engine.
  • Page 27 WG972-E2, DF972-E2, WSM G GENERAL Checking Radiator Hoses and Clamp Bands 1. Check to see if the radiator hoses are properly fixed every 200 hours of operation or every six months, whichever comes first. 2. If the clamp is loose, apply oil to the threads and retighten it securely.

  • Page 28: Check Points Of Every 1000 Hours

    WG972-E2, DF972-E2, WSM G GENERAL [6] CHECK POINTS OF EVERY 1000 HOURS Replacing the Spark Plug 1. Disconnect the spark plug cap (1). 2. Remove the spark plug. 3. Replace the new spark plug. 19.6 to 24.5 N·m Tightening torque Spark plug 2.0 to 2.5 kgf·m...
  • Page 29 WG972-E2, DF972-E2, WSM G GENERAL Adjusting the Valve Clearance ■ IMPORTANT • The valve clearance must be checked and adjusted when engine is cold. 1. Remove the cylinder head cover (1) and the spark plugs. 2. Align the “1TC” mark (2) on the flywheel and alignment mark (3) on the rear end plate so that the No.

  • Page 30: Check Points Of Every 1 Year

    WG972-E2, DF972-E2, WSM G GENERAL Checking and Relapping the Valve Seats 1. Coat the valve face lightly with prussian blue and put the valve on its seat to check the contact. 2. If the valve does not seat all the way around the valve seat or the valve contact is less than 70 %, correct the valve seating as follows.
  • Page 31 WG972-E2, DF972-E2, WSM G GENERAL Cleaning Water Jacket and Radiator Interior CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen cap slightly to the stop to relieve any excess pressure before removing cap completely.
  • Page 32 WG972-E2, DF972-E2, WSM G GENERAL Anti-Freeze • There are two types of anti-freeze available: use the permanent type (PT) for this engine. • Before adding anti-freeze for the first time, clean the radiator interior by pouring fresh, soft water and draining it a few times.

  • Page 33: Check Points Of Every 2 Years

    WG972-E2, DF972-E2, WSM G GENERAL [8] CHECK POINTS OF EVERY 2 YEARS Replacing the Intake Hose and Clamps Replace the intake hose and the clamps between the air cleaner and the carburetor. W10411400 Replacing the Fuel Hose and the Clamps (LPG Line) Replace the fuel hose and the clamps (LPG line).
  • Page 34 WG972-E2, DF972-E2, WSM G GENERAL Checking Primary Chamber (Vaporizer for LPG Fuel) ■ IMPORTANT • When checking the fuel system after completely consuming the fuel in piping. • Treat a seal tape or liquid gasket when install each connector. 1. Run the engine until is warmed up.
  • Page 35 WG972-E2, DF972-E2, WSM G GENERAL Replacing Radiator Hoses and Clamp Bands CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen cap slightly to the stop to relieve any excess pressure before removing cap completely.

  • Page 36: Special Tools

    WG972-E2, DF972-E2, WSM G GENERAL 5. SPECIAL TOOLS Timing Light Application : Use to adjust the ignition timing. W1024318 Compression Tester Code No : 07909-30251 Application : Use to measure gasoline engine compression and diagnose the engine for a major overhaul.
  • Page 37 WG972-E2, DF972-E2, WSM G GENERAL Valve Guide Replacing Tool Application: Use to press out and press fit the valve guide. 200 mm (7.87 in.) 80 mm (3.15 in.) 40 mm (1.58 in.) 20 mm dia. (0.79 in dia.) 9.96 to 9.98 mm dia. (0.3921 to 0.3929 in. dia.) 5.5 to 5.7 mm dia.
  • Page 38 WG972-E2, DF972-E2, WSM G GENERAL Crankshaft Bearing 1 Replacing Tool Application: Use to press out and press fit the crankshaft bearing 1. [Press Out] 135 mm (5.31 in.) 72 mm (2.83 in.) 40 mm radius (1.57 in. radius) 10 mm (0.39 in.) 22 mm (0.87 in.)
  • Page 39 WG972-E2, DF972-E2, WSM G GENERAL Electronic Governor Service Tool ■ NOTE • Many applications are delivered pre-configured, calibrated, and tuned. These units do not require the use of the Service Tool. The Service Tool software is used to troubleshoot the electronic governor.
  • Page 40 [6] RADIATOR CAP ..................M-13 [7] VAPORIZER (DF972-E2)................ M-13 5. FUEL SYSTEM ..................... M-14 [1] GENERAL ....................M-14 [2] CARBURETOR (WG972-E2)..............M-15 [3] DF CARBURETOR (DF972-E2) ............M-16 [4] VAPORIZER (DF972-E2)................ M-17 [5] GOVERNOR .................... M-20 [6] INLET MANIFOLD .................. M-21 [7] FUEL FILTER (FOR GASOLINE LINE) ..........

  • Page 41: Feature

    1. FEATURE In 2003, Kubota added two new compact diesel engines, Z602 and D902, to its SUPER MINI Series. WG/DF972 is two dual fuel (gasoline / LP Gas) type engine that is solidly on this world acclaimed diesel engine series.

  • Page 42: Engine Body

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 2. ENGINE BODY [1] CYLINDER BLOCK The engine has a high durability tunnel-type cylinder block in which the crank bearing component is a constructed body. Furthermore, liner less type, allow effective cooling, less...

  • Page 43: Cylinder Head

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [3] CYLINDER HEAD ■ Intake and Exhaust Port The cross-flow type intake / exhaust ports, which lower the heat conduction from the exhaust port to the intake port. The low heat conduction keeps the intake air from being heated and expanded by the exhaust gas.

  • Page 44: Piston And Piston Ring

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [5] PISTON AND PISTON RING ■ Piston Expansion Control Piston: The thermal expansion is suppressed to the minimum by the adoption of the strut (5). The piston head has the combustion chamber (1) with the concave of bathtub shaped type.

  • Page 45: Oil Pan

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [6] OIL PAN The oil pan is expanded under the gear case. Therefore, the height of the engine can be lowered more than so far while securing a necessary amount of oil. (1) Gear Case...

  • Page 46: Fuel Camshaft

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [9] FUEL CAMSHAFT The camshaft (10) is equipped with steel ball (2) to control the governor.. Power can be taken out from this shaft. (Side PTO). (1) Injection Pump Gear (7) Stopper (2) Steel Ball...

  • Page 47: Flywheel

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [12] FLYWHEEL The flywheel (2) is connected with the crankshaft (1), it stores the rotaing force in the combustion stroke as inertial energy to rotate the crankshaft smoothly. The flywheel periphery is provided with marks showing fuel injection timing and top dead center.

  • Page 48: Lubricating System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 3. LUBRICATING SYSTEM [1] GENERAL The lubricating system consists of an oil strainer, an oil pump, a relief valve, an oil filter cartridge and an oil pressure switch. The oil pump sucks the lubricating oil in the oil pan through the strainer and sends it to the oil filter cartridge, where the oil is further filtered.

  • Page 49: Oil Pump

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [2] OIL PUMP The oil pump is a trochoid pump, whose rotors have trochoid lobes. The inner rotor (3) has 4 lobes and the outer rotor (4) has 5 lobes, and they are eccentrically engaged with each other.

  • Page 50: Oil Pressure Switch

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [5] OIL PRESSURE SWITCH The oil pressure switch is mounted on the cylinder block and is led to the lubricating oil passage. When the oil pressure falls below the specified value, the oil pressure warning lamp lights.

  • Page 51: Cooling System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 4. COOLING SYSTEM [1] GENERAL The cooling system consists of a radiator (1), a centrifugal water pump (4), a suction fan (2) and a thermostat (3). The coolant is cooled through the radiator core, and the fan behind the radiator pulls the cooling air through the core to improve cooling.

  • Page 52: Thermostat

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [4] THERMOSTAT The thermostat is of the wax pellet type. The thermostat controls the flow of the coolant to the radiator to keep the proper temperature. The case (1), which serves as a valve seat (1), has a spindle inserted in the pellet (3) which is installed to the valve (2).

  • Page 53: Radiator Cap

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [6] RADIATOR CAP The pressure type radiator cap prevents differences in pressure between the inside and the outside of the radiator from deforming the radiator. When the coolant temperature rises and the pressure...

  • Page 54: Fuel System

    The fuel is fed from the fuel tank (1) through the fuel filter (3) to the carburetor (6) by the fuel feed pump (4). DF972-E2: This fuel system has 2 ways. Gasoline fuel is the same as WG972-E2. For LPG fuel, the liquid fuel stored in the LPG tank (4) is sent to vaporizer (10) by pressure in the gaseous phase in the tank through the fuel filter (12) and shut off valve (11).

  • Page 55: Carburetor (Wg972-E2

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [2] CARBURETOR (WG972-E2) (1) Choke Lever (2) Venturi (3) Throttle Shaft (4) Main Air Jet (5) Throttle Valve (6) Main Nozzle (7) Bleeder Hole (8) Float Chamber Gasket (9) Float (10) Float Chamber...

  • Page 56: Df Carburetor (Df972-E2

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [3] DF CARBURETOR (DF972-E2) ■ NOTE • DF Carburetor operates the same as a gasoline carburetor in gasoline fuel. With the fuel select switch (8) in the "GASOLINE" position (D) and the main switch in the "ON" position, the battery current flows to the gasoline cut off solenoid (6).

  • Page 57: Vaporizer (Df972-E2

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [4] VAPORIZER (DF972-E2) Vaporizer is a device which converts the liquid fuel into the gaseous fuel and the following structures and functions are possessed. ■ Primary Chamber liquid fuel decompressed (the first decompression) and it is evaporated.
  • Page 58 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ■ Secondary Chamber The fuel adjusted with primary chamber to the specified pressure enters secondary chamber (5) between secondary valve (1) and the valve seat (2) and is decompressed to the vicinity of the atmospheric pressure almost.
  • Page 59 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ■ Vacuum Lock Chamber 1) Operation when engine stops Because pressure on the vacuum lock chamber (3) side and the secondary chamber (4) side is equal, vacuum lock diaphragm (5) is pushed to the second chamber side by the tension of vacuum lock diaphragm spring (2).

  • Page 60: Governor

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [5] GOVERNOR The engine is equipped with a centrifugal ball mechanical governor which activates the throttle in response to engine speed. When the engine is carrying a load and running at rated speed, the speed will drop if the load is increased even slightly.

  • Page 61: Inlet Manifold

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [6] INLET MANIFOLD Part of coolant heated in the water jacket is channeled to the inlet manifold, where the hot coolant heats the fuel-air mixture for better carburetion. Heating effect is particularly good when the engine is running at low speeds and with light load is cold weather, thus improving fuel economy and acceleration.

  • Page 62: Ignition System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 6. IGNITION SYSTEM [1] DEGITAL IGNITION SYSTEM ■ General The function of an ignition system is to provide the electrical spark that ignites the air/fuel mixture in the cylinder at precisely the correct time.

  • Page 63: Electrical System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 7. ELECTRICAL SYSTEM [1] STARTING SYSTEM ■ Staeter The starter is the electromagnetic drive type. DC, Series-wound, Electromagnetic Type of motor drive Nominal output Nominal output 1.0 kW 30 seconds (Do not rotate continuously Nominal output for longer periods.)

  • Page 64: Charging System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ■ Key Switch The key switch has 4 positions. The terminal "30" is connected to the battery. It is released at the "STARTER" position and returns to the "ON" position. [START] When the key is turned to the "START" position, through the "ON"...
  • Page 65 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ■ Regulator The regulator performs rectification and voltage regulation. The regulator converts AC into DC which flows through the power consuming circuits and the battery, and also charges the battery. If however, the battery voltage exceeds a certain level.
  • Page 66 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ■ Charging Machanism The charging mechanism is described in four sections: 1. When key switch is "ON". 2. At starting 3. In charging 4. Over-charge protection (1) GEN: Magnet type AC generator (2) LAMP:...
  • Page 67 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 3. In Charging Because BATT terminal voltage just after engine start is lower than setting value (14 to 15 V), or lower than zener level of Z1, current is not supplied to base of Q4 and Q4 is off, as shown in figure (B).

  • Page 68: Solenoid

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [3] SOLENOID When the key switch is turned on, a current flows to the solenoid, which in turn opens the solenoid valve. When the key switch is turned off, the solenoid valve closes, blocking the gasoline main jet (2) / LPG main jet (4).

  • Page 69: Electronic Governor

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 8. ELECTRONIC GOVERNOR Electronic governor combines the electric actuator with integrated speed control software to control the speed of the engine. Electronic governor is a microprocessor-based control that is incorporated into the actuator, creating a single integrated package. This eliminates the need for an additional driver box and speed control box.
  • Page 70 SERVICING CONTENTS 1. TROUBLESHOOTING ..................S-1 [1] FOR GASOLINE FUEL ................S-1 [2] FOR LPG FUEL ..................S-2 [3] FOR ELECTRONIC GOVERNOR ............S-3 2. SERVICING SPECIFICATIONS ..............S-6 3. TIGHTENING TORQUES ................S-12 [1] TIGHTENING TORQUES FOR SPECIAL USE SCREWS, BOLTS AND NUTS....................S-12 [2] TIGHTENING TORQUES FOR GENERAL USE SCREWS, BOLTS AND NUTS....................S-13 4.

  • Page 71: Troubleshooting

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 1. TROUBLESHOOTING [1] FOR GASOLINE FUEL Reference Symptom Probable Cause Solution Page Engine Will Not Turn Engine jammed Check engine to find – Over the problem and repair it Battery discharged Charge –...

  • Page 72: For Lpg Fuel

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Reference Symptom Probable Cause Solution Page Engine Speed Does Incorrect governor adjustment Adjust S-20 Not Increase Defective ignitor Replace S-26 Incorrect carburetor adjustment Adjust S-20 Clogged air cleaner Clean or replace G-16 Defection Output...

  • Page 73: For Electronic Governor

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [3] FOR ELECTRONIC GOVERNOR ■ NOTE • This troubleshooting describe the procedure which does not use the service tool (soft wear). Engine does not start : Step 1 (1) Refer to [Adjust Governor Lever of Electronic Governor]...
  • Page 74 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Engine does not start : Step 2 (1) Refer to the [Air Gap of Engine Speed Sensor for Electronic Governor] (2) Refer to the [Resistance of Engine Speed Sensor for Electronic Governor] KiSC issued 01, 2006 A...
  • Page 75 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Engine unstable (1) Refer to the [Adjust Governor Lever of Electronic Governor] KiSC issued 01, 2006 A...

  • Page 76: Servicing Specifications

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 2. SERVICING SPECIFICATIONS ENGINE BODY Item Factory Specification Allowable Limit Valve Clearance (Cold) 0.145 to 0.185 mm – 0.00571 to 0.00728 in. Compression Pressure – 1.27 MPa 0.88 MPa 13.0 kgf/cm 9.0 kgf/cm...
  • Page 77 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Valve Spring Free Length 31.3 to 31.8 mm 28.4 mm 1.232 to 1.252 in. 1.118 in. Tilt – 1.2 mm 0.047 in. Setting Load / 64.7 N / 27.0 mm...
  • Page 78 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Camshaft Journal to Cylinder Block Bore Oil Clearance 0.050 to 0.091 mm 0.15 mm 0.00197 to 0.00358 in. 0.0059 in. Camshaft Journal O.D. 32.934 to 32.950 mm –...
  • Page 79 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Crankpin to Crankpin Bearing Oil Clearance 0.020 to 0.051 mm 0.15 mm 0.00079 to 0.00201 in. 0.0059 in. Crankpin O.D. 33.959 to 33.975 mm –...
  • Page 80 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE LUBRICATING SYSTEM Item Factory Specification Allowable Limit Engine Oil Pressure At Idle Speed More than 49 kPa – 0.5 kgf/cm 7 psi At Rated Speed 196 to 441 kPa 147 kPa 2.0 to 4.5 kgf/cm 1.5 kgf/cm...
  • Page 81 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE ELECTRICAL SYSTEM Item Factory Specification Allowable Limit Starter Commutator 32.0 mm 31.0 mm (O.D.) 1.260 in. 1.220 in. Difference Less than 0.5 mm 0.4 mm (O.D.) 0.002 in. 0.016 in. Mica 0.5 to 0.8 mm 0.2 mm...

  • Page 82: Tightening Torques

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 3. TIGHTENING TORQUES Screws, bolts and nuts must be tightened to the specified torque using a torque wrench, several screws, bolts and nuts such as those used on the cylinder head must be tightened in proper sequence and the proper torque.

  • Page 83: Tightening Torques For General Use Screws, Bolts And Nuts

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [2] TIGHTENING TORQUES FOR GENERAL USE SCREWS, BOLTS AND NUTS When the tightening torques are not specified, tighten the screws, bolts and nuts according to the table below. Grade Standard Screw and Bolt...

  • Page 84: Checking, Disassembling And Servicing

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE 4. CHECKING, DISASSEMBLING AND SERVICING [1] CHECKING AND ADJUSTING (1) Engine Body Compression Pressure 1. Run the engine until it is warmed up. 2. Stop the engine. 3. Remove the air cleaner, the muffler and all spark plugs.
  • Page 85 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Top Clearance 1. Remove the cylinder head. (Do not attempt to remove the cylinder head gasket.) 2. Move the piston up and stick a strip of fuse [1.5 mm dia. (0.059 in. dia.), 5 to 7 mm long (0.197 to 0.276 in. long)] on the piston head at three positions with grease so as to avoid the intake and exhaust valves and the combustion chamber ports.
  • Page 86 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Adjusting the Valve Clearance ■ IMPORTANT • The valve clearance must be checked and adjusted when engine is cold. 1. Remove the cylinder head cover (1) and the spark plugs. 2. Align the “1TC” mark (2) on the flywheel and alignment mark (3) on the rear end plate so that the No.

  • Page 87: Lubricating System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (2) Lubricating System Engine Oil Pressure 1. Remove the engine oil pressure switch, and set an oil pressure tester. 2. Start the engine. After warming up, measure the oil pressure of both idling and rated speeds.
  • Page 88 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Fan Belt Damage and Wear 1. Check the fan belt for damage. 2. If the fan belt is damaged, replace it. 3. Check if the fan belt is worn and sunk in the pulley groove.
  • Page 89 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE CAUTION • When removing the radiator cap, wait at least ten minutes after the engine has stopped and cooled down. Otherwise, hot water may gush out, scalding nearby people. Radiator Cap Air Leakage 1.

  • Page 90: Fuel System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (4) Fuel System Adjusting Governor 1. Loosen the governor lever nut (3). 2. Set the throttle valve to the fully "OPEN" position with the governor lever (1), turn the groove on the governor lever shaft (2) fully clockwise with a screwdriver (to open the governor completely), and then tighten the nut (3) in this position.
  • Page 91 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Carburetor (WG972-E2) Dual Fuel Carburetor (DF972-E2) The carburetor is tamper resistant; the idle mixture screw has been covered by tamper plug after adjustment at the factory. (1) Tamper Resistance W1017786 Replacement of Altitude Compensation Kit (Main Jet and Pilot Jet) 1.
  • Page 92 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE LPG Vaporizer Regulator (DF972-E2) LPG vaporizer regulator is tamper resistant; the main and idle pressure adjustment screws have been covered by tamper caps after adjustment at the factory. (1) Tamper Resistance W10371670 Vaporizer Joints (DF972-E2) 1.
  • Page 93 NOTE • The LPG liquid in joint (fitting) to the vaporizer / regulator is not provided in the KIT by KUBOTA, due to the many different connection requirements by the OEM. The female thread into the vaporizer / regulator is a PT 1/4 METRIC thread.

  • Page 94: Ignition System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (5) Ignition System Timing Light Test 1. Set the timing light to High-tension cord. 2. Close the fuel cocks. 3. Cranking the engine. 4. If the timing light blinks, the spark plug and ignition coil are normal.
  • Page 95 • The described numerical value is the values of KBT parts. • Checking sensor as described in the manual of sensor maker. • The described valve is the data of supply of kubota. Follow the instruction of OEM for parts adopted by OEM. W1019297 Resistance of Engine Speed Sensor for Electronic Governor 1.
  • Page 96 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Resistance of Ignitor 1. Disconnect the connector. 2. Measure the resistance with an ohmmeter. 3. If the resistance is not with in the factory specifications, replace it. W1109304 Ignitor Check Chart Negative Positive 10 to 40 kΩ...

  • Page 97: Electrical System

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (6) Electrical System Motor Test CAUTION • Secure the starter to prevent it from jumping up and down while testing the motor. 1. Disconnect the battery negative cable from the battery. 2. Disconnect the battery positive cable from the battery.
  • Page 98 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Magnet Switch Continuity Test 1. Check the continuity across the C terminal (1) and the B terminal (2) with a circuit tester, pushing in the plunger. 2. If not continuous or if a certain value is indicated, replace the magnet switch.
  • Page 99 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Continuity across Regulator’s Terminals 1. Measure with a circuit tester according to the list below. ■ NOTE • For this test, use only Analog Meter and do not use a high voltage tester such as a MΩ meter.
  • Page 100 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Alternator on Unit Test (Before testing) • Before alternator on unit test, check the battery terminal connections, circuit connection, fan belt tension, charging indicator lamp, fuses on the circuit, and abnormal noise from the alternator.

  • Page 101: Electronic Governor

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (7) Electronic Governor Adjust Governor Lever 1. Loosen the idling speed screw (1). 2. Loosen the governor lever nut (4). 3. Turn the actuator shaft (3) fully counterclockwise. 4. Turn the governor lever (5) fully counterclockwise.

  • Page 102: Disassembling And Assembling

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [2] DISASSEMBLING AND ASSEMBLING ■ IMPORTANT • When reassembling, replace all of the O-rings and gaskets by new ones. • When disassembling the LPG engine after completely consuming the fuel in piping. (1) Draining Coolant and Engine Oil...

  • Page 103: External Components

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (2) External Components Alternator, Starter and Others 1. Remove the air cleaner and muffler. 2. Remove the cooling fan (1), fan pulley and fan belt (2). 3. Remove the alternator. 4. Remove the starter.
  • Page 104 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Carburetor (Mechanical Governor) 1. Disconnect the connector of LPG solenoid (for DF972) (4) and the connector of gasoline solenoid (3). 2. Disconnect the breather hose (4). 3. Remove the air cleaner flange (2) and air cleaner gasket.
  • Page 105 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Adjust Governor Lever (Electronic Governor) 1. Loosen the idling speed screw (1). 2. Loosen the governor lever nut (4). 3. Turn the actuator shaft (3) fully counterclockwise. 4. Turn the governor lever (5) fully counterclockwise.
  • Page 106 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Actuator (Electronic Governor) 1. Remove the actuator mounting screw (1). 2. Remove the actuator (2). 3. Remove the actuator flange screw (4). 4. Remove the actuator flange (3). 4.9 to 5.4 N·m Tightening torque Actuator mounting screw 0.45 to 0.55 kgf·m...

  • Page 107: Cylinder Head, Valves And Oil Pan

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Ignition Coil and Spark Plug 1. Disconnect the plug cap (1). 2. Disconnect the connector of ignition coil (3). 3. Remove the ignition coil (2). A : for No. 1 cylinder B : for No. 2 cylinder C : for No.
  • Page 108 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Rocker Arm and Push Rod 1. Remove the rocker arm bracket screws (1). 2. Detach the rocker arm assembly (2). 3. Remove the push rods (3). (When reassembling) • When putting the push rods (3) onto the tappets (4), check to see if their ends are properly engaged with the dimples.
  • Page 109 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Valves 1. Remove the valve caps (2). 2. Remove the valve spring collet (3), pushing the valve spring retainer (4) by valve spring replacer (1). 3. Remove the valve spring retainer (4), valve spring (5) and valve stem seal (6).

  • Page 110: Thermostat

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Pan and Oil Strainer 1. Remove the oil pan mounting screws (1). 2. Remove the oil pan (2) by lightly tapping the rim of the pan with a wooden hammer. 3. Remove the oil strainer (3).

  • Page 111: Timing Gear, Camshaft And Fuel Camshaft

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (5) Timing Gear, Camshaft and Fuel Camshaft Speed Control Plate 1. Remove the screws (1) and separate the speed control plate (2). (When reassembling) • Remove the speed control plate (for mechanical governor only) (2) and make sure that the governor lever shaft (3) is correctly set in the governor fork (4).
  • Page 112 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Water Pump Assembly 1. Remove the water pump assembly from the gear case cover. (When reassembling) • Apply a liquid gasket (Three Bond 1215 or equivalent) to both sides of gasket (3). (1) Water Pump Flange...

  • Page 113: Piston And Connecting Rod

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Fuel Camshaft 1. Remove the retaining plate (4). 2. Remove the fork lever holder (for mechanical governor only) mounting screws (6), then draw out the injection pump gear (1) and fuel camshaft (5) with the governor fork assembly.
  • Page 114 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Piston 1. Turn the flywheel and bring the piston to top dead center. 2. Draw out the piston upward by lightly tapping it from the bottom of the crankcase with the grip of a hammer.

  • Page 115: Crankshaft

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Piston Ring and Connecting Rod 1. Remove the piston rings using a piston ring tool. 2. Remove the piston pin (10), and separate the connecting rod (8) from the piston (7). (When reassembling) •...
  • Page 116 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Bearing Case Cover ■ NOTE • Remove the bearing case cover mounting screws. First, remove inside screws (1) and then outside screws (2). 2. Remove the bearing case cover (6). (When reassembling) • Fit the bearing case gasket (3) and the bearing case cover gasket (4) with correct directions.
  • Page 117 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Crankshaft Assembly 1. Remove the main bearing case screw 2 (1). 2. Turn the crankshaft to set the crankpin of the third cylinder to the bottom dead center. Then draw out the crankshaft until the crankpin of the second cylinder comes to the center of the third cylinder.
  • Page 118 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Main Bearing Case Assembly 1. Remove the two main bearing case screws 1 (4), and remove the main bearing case assembly 1 (1), being careful with crankshaft bearing 3 (5) (9). 2. Remove the main bearing case assembly 2 (2) and the main bearing case assembly (3) as above.

  • Page 119: Starter

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (8) Starter (1) Solenoid Switch mounting Nut (2) Starter Drive Housing (3) Drive lever (4) Gasket (5) Solenoid Switch (6) C Terminal Nut (7) Snap Ring (8) Overrunning Clutch (9) Armature (10) Brush Spring...

  • Page 120: Servicing

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE [3] SERVICING (1) Cylinder Head and Valves Cylinder Head Surface Flatness 1. Clean the cylinder head surface. 2. Place a straightedge on the cylinder head’s four sides and two diagonal as shown in the figure.
  • Page 121 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Valve Recessing 1. Clean the cylinder head, the valve face and seat. 2. Insert the valve into the valve guide. 3. Measure the valve recessing with a depth gauge. 4. If the measurement exceeds the allowable limit, replace the valve.
  • Page 122 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Replacing Valve Guide (When removing) 1. Press out the used valve guide using a valve guide replacing tool. (When installing) 1. Clean a new valve guide and valve guide bore, and apply engine oil to them.
  • Page 123 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Correcting Valve and Valve Seat ■ NOTE • Before correcting the valve and seat, check the valve stem and the I.D. of valve guide section, and repair them if necessary. • After correcting the valve seat, be sure to check the valve recessing.
  • Page 124 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Free Length and Tilt of Valve Spring 1. Measure the free length (B) of valve spring with vernier calipers. If the measurement is less than the allowable limit, replace it. 2. Put the spring on a surface plate, place a square on the side of the spring.

  • Page 125: Timing Gear, Camshaft

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Push Rod Alignment 1. Place the push rod on V blocks. 2. Measure the push rod alignment. 3. If the measurement exceeds the allowable limit, replace the push rod. 0.25 mm Push rod alignment Allowable limit 0.0098 in.
  • Page 126 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Idle Gear Side Clearance 1. Set a dial indicator with its tip on the idle gear. 2. Measure the side clearance by moving the idle gear to the front and rear. 3. If the measurement exceeds the allowable limit, replace the idle gear collar.
  • Page 127 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Clearance of Camshaft Journal 1. Measure the camshaft journal O.D. with an outside micrometer. 2. Measure the cylinder block bore I.D. for camshaft with a inside micrometer, and calculate the oil clearance.

  • Page 128: Piston And Connecting Rod

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (3) Piston and Connecting Rod Piston Pin Bore I.D. 1. Measure the piston pin bore I.D. in both the horizontal and vertical directions with a cylinder gauge. 2. If the measurement exceeds the allowable limit, replace the piston.
  • Page 129 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Piston Ring Gap 1. Insert the piston ring into the lower part of the cylinder (the least worn out part) with a piston ring compressor and piston. 2. Measure the ring gap with a feeler gauge.

  • Page 130: Crankshaft

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (4) Crankshaft Crankshaft Side Clearance 1. Set a dial indicator with its tip on the end of the crankshaft. 2. Measure the side clearance by moving the crankshaft to the front and rear.
  • Page 131 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Clearance between Crankpin and Crankpin Bearing 1. Clean the crankpin and crankpin bearing. 2. Put a strip of plastigage on the center of the crankpin. 3. Install the connecting rod cap and tighten the connecting rod screws to the specified torque, and remove the cap again.
  • Page 132 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Clearance between Crankshaft Journal and Crankshaft Bearing 1 1. Measure the O.D. of the crankshaft front journal with an outside micrometer. 2. Measure the I.D. of the crankshaft bearing 1 with an inside micrometer, and calculate the oil clearance.
  • Page 133 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Clearance between Crankshaft Journal and Crankshaft Bearing 2 (Crankshaft Bearing 3) 1. Put a strip of plastigage on the center of the journal. 2. Install the bearing case and tighten the bearing case screws 1 to the specified torque, and remove the bearing case again.

  • Page 134: Cylinder

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Oil Clearance between Crankshaft Journal and Crankshaft Bearing 2 and Crankshaft Bearing 3 (Continued) (Reference) • Undersize crankshaft bearing 2 and 3 Oversize Bearing Code Number Marking Crankshaft bearing 2 02 15694-23930 020 US...

  • Page 135: Oil Pump

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Correcting Cylinder (Oversize) 1. When the cylinder is worn beyond the allowable limit, bore and hone it to the specified dimension. 75.000 to 75.019 mm Factory spec. 2.95276 to 2.95350 in. Cylinder liner I.D.

  • Page 136: Starter

    WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE (7) Starter Overrunning Clutch 1. Inspect the pinion for wear or damage. 2. If there is any defect, replace the overrunning clutch assembly. 3. Check that the pinion turns freely and smoothly in the overrunning direction and does not slip in the cranking direction.
  • Page 137 WG972-E2, DF972-E2, WSM GASOLINE / LPG ENGINE Brush Holder 1. Check the continuity across the brush holder and the holder support with an ohmmeter. 2. If it conducts, replace the brush holder. W1076066 Armature Coil 1. Check the continuity across the commutator and armature coil core with an ohmmeter.
  • Page 138 EDITOR : KUBOTA FARM & INDUSTRIAL MACHINERY SERVICE, LTD. 64, ISHIZU-KITAMACHI, SAKAI-CITY, OSAKA, 590-0823, JAPAN PHONE : ( 81 ) 72-241-1129 : ( 81 ) 72-245-2484 E-mail : ksos-pub@kubota.co.jp Printed in Japan 2006. 01, S, EI, E I , e Code No.97897-02672...

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