Kubota WG1903-E3 Workshop Manual
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Kubota WG1903-E3 Workshop Manual

Kubota WG1903-E3 Workshop Manual

Gasoline, lpg, natural gas engine
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WORKSHOP MANUAL
GASOLINE,LPG,
NATURAL GAS ENGINE
WG1903-E3,
WG2503-E3
KiSC issued 05, 2019 A

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Summary of Contents for Kubota WG1903-E3

  • Page 1 WORKSHOP MANUAL GASOLINE,LPG, NATURAL GAS ENGINE WG1903-E3, WG2503-E3 KiSC issued 05, 2019 A...
  • Page 2 TO THE READER This Workshop Manual tells the servicing personnel about the mechanism, servicing and maintenance of the WG1903-E3 and WG2503-E3. It contains 4 parts: "Information", "General", "Mechanism" and "Servicing".  Information This section contains information below. • Safety First •...

  • Page 3: Additional Information

    ADDITIONAL INFORMATION In this workshop manual, the engine models are divided into two groups as follows and used. Group name Engine model Standard model WG1903-G-E3 WG1903-N-E3 WG1903-GL-E3 WG2503-G-E3 WG2503-L-E3 WG2503-N-E3 WG2503-GL-E3 WG2503-LN-E3 LM model WG1903-L-E3LM WG2503-GL-E3LM KiSC issued 05, 2019 A...
  • Page 4 Record of Revisions For pdf, use search function {Search word} to find all the revised locations. Last digit Month of Reference of the Main Revised Point and Corrective Measures {Search word} Revision Page Code No. 2014.04 6. WIRING DIAGRAM changed –...
  • Page 5 INFORMATION KiSC issued 05, 2019 A...

  • Page 6: Table Of Contents

    INFORMATION CONTENTS 1. SAFETY FIRST ..........................I-1 2. SPECIFICATIONS.......................... I-4 3. IMPORTANT ITEMS OF EXHAUST EMISSION REGULATION..........I-11 [1] THREE-WAY CATALYST ...................... I-12 [2] VAPORIZER AND LOCK OFF VALVE................... I-12 [3] LENGTH OF THE VAPOR HOSE ..................I-12 [4] IMPORTANT NOTICE ......................I-12 [5] EMISSION-RELATED INSTALLATION INSTRUCTIONS............

  • Page 7: Safety First

    INFORMATION WG1903-E3, WG2503-E3, WSM 1. SAFETY FIRST SAFETY FIRST • This symbol, the industry's "Safety Alert Symbol", is used throughout this manual and on labels on the machine itself to warn of the possibility of personal injury. Read these instructions carefully.
  • Page 8 INFORMATION WG1903-E3, WG2503-E3, WSM OPERATE SAFELY • Do not use the machine after you consume alcohol or medication or when you are tired. • Put on applicable clothing and safety equipment. • Use applicable tools only. Do not use alternative tools or parts.
  • Page 9 INFORMATION WG1903-E3, WG2503-E3, WSM DISCARD FLUIDS CORRECTLY • Do not discard fluids on the ground, down the drain, into a stream, pond, or lake. Obey related environmental protection regulations when you discard oil, fuel, coolant, electrolyte and other dangerous waste.

  • Page 10: Specifications

    *The specification described above is of the standard engine of each model. *Conversion Formula: HP = 0.746 kW, PS = 0.7355 kW *KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS • Commercial Propane gas only. • Equivalent to Propanes H-D-5 of GPA* standards.
  • Page 11 *The specification described above is of the standard engine of each model. *Conversion Formula: HP = 0.746 kW, PS = 0.7355 kW *KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS • Commercial Propane gas only. • Equivalent to Propanes H-D-5 of GPA* standards.
  • Page 12 *The specification described above is of the standard engine of each model. *Conversion Formula: HP = 0.746 kW, PS = 0.7355 kW *KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS • Commercial Propane gas only. • Equivalent to Propanes H-D-5 of GPA* standards.
  • Page 13 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-N-E3 Model Natural gas fuel Number of Cylinder Type Vertical, water cooled, 4-cycle natural gas engine Bore × Stroke 88.0 × 102.4 mm (3.46 × 4.031 in.) Total Displacement 2.491 L (152.0 cu.in.) SAE Gross Intermittent 42.4 kW (56.9 HP) / 2700 min...
  • Page 14 *The specification described above is of the standard engine of each model. *Conversion Formula: HP = 0.746 kW, PS = 0.7355 kW *KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS • Commercial Propane gas only. • Equivalent to Propanes H-D-5 of GPA* standards.
  • Page 15 *The specification described above is of the standard engine of each model. *Conversion Formula: HP = 0.746 kW, PS = 0.7355 kW *KUBOTA RECOMMENDED LPG FUEL SPECIFICATIONS • Commercial Propane gas only. • Equivalent to Propanes H-D-5 of GPA* standards.
  • Page 16 ECU. This is necessary due to the specific variation of the calorific value of available fuel at each well location. The operable limits of Wobbe Index*1 value fuel for the Kubota large spark ignited (LSI) engines when used in wellhead applications is: 40.66 to 61.17 MJ/m (1090 to 1640 BTU/ft *2).

  • Page 17: Important Items Of Exhaust Emission Regulation

    INFORMATION WG1903-E3, WG2503-E3, WSM 3. IMPORTANT ITEMS OF EXHAUST EMISSION REGULATION WG1903 and WG2503 are available and unavailable in those countries. North kW, Disp. Model Type Europe Japan America 19 < P, 1.0 < L WG1903-E3, WG2503-E3 Available Available Non-available Current and future emission regulations.

  • Page 18: Three-Way Catalyst

    Vaporizer requires a normally-closed electrically controlled fuel lock off valve that is close coupled to the vaporizer and off when ignition switch is off or when the engine is not running normally (supplied from KUBOTA). In operation without a lock off upstream the vaporizer will flow fuel with the engine off. The vaporizer is not a fuel shut-off safety device.

  • Page 19: Engine Control Unit (Ecu

    INFORMATION WG1903-E3, WG2503-E3, WSM (6) Engine Control Unit (ECU) Installation must use all 4 of the vibration mounts. ECU header pins must be horizontal or point downward. 9Y1210914INI0013US0 (7) Vehicle Interface Connectors Vehicle interface connectors shall be connected with your wire harness.

  • Page 20: Performance Curves

    INFORMATION WG1903-E3, WG2503-E3, WSM 4. PERFORMANCE CURVES WG1903-G/N/GL (1) Brake Horsepower (4) Torque (6) Gross Intermittent Brake (a) Gasoline Use (2) Engine Speed (5) Gross Intermittent Torque Horsepower (b) LP Gas Use (3) Specific Fuel Consumption (7) Gross Intermittent Specific...
  • Page 21 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-L-E3LM (1) Brake Horsepower (4) Torque (6) Gross Intermittent Brake (a) LP Gas Use (2) Engine Speed (5) Gross Intermittent Torque Horsepower (3) Specific Fuel Consumption (7) Gross Intermittent Specific Fuel Consumption 9Y1210914INI0033US0 I-15 KiSC issued 05, 2019 A...
  • Page 22 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-G/L/N/GL-E3 (1) Brake Horsepower (4) Torque (6) Gross Intermittent Brake (a) Gasoline Use (2) Engine Speed (5) Gross Intermittent Torque Horsepower (b) LP Gas Use (3) Specific Fuel Consumption (7) Gross Intermittent Specific (c) Natural Gas Use...

  • Page 23: Dimensions

    INFORMATION WG1903-E3, WG2503-E3, WSM 5. DIMENSIONS WG1903-G-E3 9Y1210914INI0034US0 I-17 KiSC issued 05, 2019 A...
  • Page 24 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-GL-E3 9Y1210914INI0035US0 I-18 KiSC issued 05, 2019 A...
  • Page 25 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-L-E3LM 9Y1210914INI0036US0 I-19 KiSC issued 05, 2019 A...
  • Page 26 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-N-E3 9Y1210914INI0037US0 I-20 KiSC issued 05, 2019 A...
  • Page 27 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-GL 9Y1210914INI0019US0 I-21 KiSC issued 05, 2019 A...
  • Page 28 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-G 9Y1210914INI0026US0 I-22 KiSC issued 05, 2019 A...
  • Page 29 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-L/N 9Y1210914INI0027US0 I-23 KiSC issued 05, 2019 A...

  • Page 30: Wiring Diagram

    INFORMATION WG1903-E3, WG2503-E3, WSM 6. WIRING DIAGRAM WG1903-G I-24 KiSC issued 05, 2019 A...
  • Page 31 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-GL I-25 KiSC issued 05, 2019 A...
  • Page 32 INFORMATION WG1903-E3, WG2503-E3, WSM WG1903-L, WG1903-N I-26 KiSC issued 05, 2019 A...
  • Page 33 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-G-E3 I-27 KiSC issued 05, 2019 A...
  • Page 34 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-L, WG2503-N I-28 KiSC issued 05, 2019 A...
  • Page 35 INFORMATION WG1903-E3, WG2503-E3, WSM WG2503-GL-E3 I-29 KiSC issued 05, 2019 A...
  • Page 36 GENERAL KiSC issued 05, 2019 A...
  • Page 37 GENERAL CONTENTS 1. ENGINE IDENTIFICATION ......................G-1 [1] ENGINE MODEL NAME, CODE NUMBER AND ENGINE SERIAL NUMBER ...... G-1 [2] E3 ENGINE ..........................G-3 [3] CYLINDER NUMBER ......................G-3 [4] CONVERTER ......................... G-4 2. GENERAL PRECAUTIONS......................G-5 3. MAINTENANCE CHECK LIST ..................... G-6 4.

  • Page 38: Engine Identification

    GENERAL WG1903-E3, WG2503-E3, WSM 1. ENGINE IDENTIFICATION [1] ENGINE MODEL NAME, CODE NUMBER AND ENGINE SERIAL NUMBER You must identify the engine model name and serial number before you start a job. When you get in touch with the manufacturer, always tell your engine model name and serial number.
  • Page 39 GENERAL WG1903-E3, WG2503-E3, WSM (Continued) Production Month and Lot Number Month Engine Lot Number January A0001 ~ A9999 B0001 ~ February C0001 ~ C9999 D0001 ~ March E0001 ~ E9999 F0001 ~ April G0001 ~ G9999 H0001 ~ J0001 ~ J9999...

  • Page 40: E3 Engine

    Non-Road Emission regulations depends on the engine displacement and output classification. Over the past several years, KUBOTA has been supplying SI engines that comply with regulations in the respective countries affected by Non-Road Emission regulations. For KUBOTA Engines, E3 will be the designation that identifies engine models affected by the next emission phase (See the table below).

  • Page 41: Converter

    GENERAL WG1903-E3, WG2503-E3, WSM [4] CONVERTER KUBOTA provides the converter as the catalyst parts. The parts number and the manufacturing date are marked on surfaces of the catalyst parts as the catalyst identification. IMPORTANT • To trace of the converter, put down the catalyst identification and engine identification when new service converter is installed.

  • Page 42: General Precautions

    You must install the screws, bolts and nuts in their initial position to prevent the reassembly errors. • When it is necessary to use special tools, use KUBOTA special tools. Refer to the drawings when you make special tools that you do not use frequently.

  • Page 43: Maintenance Check List

    GENERAL WG1903-E3, WG2503-E3, WSM 3. MAINTENANCE CHECK LIST To make sure that the engine operates safely for a long time, refer to the table below to do regular inspections. (The schedule applies to an engine in use under normal conditions.)

  • Page 44: Check And Maintenance

    GENERAL WG1903-E3, WG2503-E3, WSM 4. CHECK AND MAINTENANCE [1] DAILY CHECK POINTS Check of Engine Oil Level 1. Make the engine level. 2. Pull out the dipstick (1) and clean it. Put in and pull it out again. Make sure that the oil level is between the 2 notches.
  • Page 45 GENERAL WG1903-E3, WG2503-E3, WSM Check of Coolant Level and Replenishment CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen the cap slightly to release unwanted pressure before you remove the cap fully. 1. Without recovery tank: Remove the radiator cap (1) and make sure that the coolant level is immediately below the port.
  • Page 46 GENERAL WG1903-E3, WG2503-E3, WSM Check of Air Cleaner Element (If necessary) 1. Remove the dust cup in the air cleaner. 2. Examine the dust in the dust cup and the element. (When reassembling) • Install the air cleaner dust cup with "TOP" indicated on the rear of the cup.
  • Page 47 GENERAL WG1903-E3, WG2503-E3, WSM Check of Fan Belt (for Standard Model) 1. Check if the fan belt is worn out and sunk in the pulley groove, and if it is, replace it. 2. Push the belt halfway between the fan drive pulley and alternator pulley at a specified force 98 N (10 kgf, 22 lbf) to measure the deflection (1).

  • Page 48: Check Points Of Initial 50 Hours

    5. Fill the engine oil until the specified level. IMPORTANT • To prevent serious damage to the engine, use only KUBOTA genuine filters or its equivalent. (1) Oil Filter Cartridge 9Y1210914GEG0012US0 G-11...

  • Page 49: Check Points Of Every 50 Hours

    GENERAL WG1903-E3, WG2503-E3, WSM [3] CHECK POINTS OF EVERY 50 HOURS CAUTION • Stop the engine before you do the check and replace below. • Make sure to check the fuel line periodically. The fuel line is subject to wear and aging, fuel may leak out onto the running engine, causing a fire.

  • Page 50: Check Points Of Every 100 Hours

    GENERAL WG1903-E3, WG2503-E3, WSM [4] CHECK POINTS OF EVERY 100 HOURS Cleaning of Air Cleaner Element 1. Remove the air cleaner element. 2. Use clean dry compressed air on the inner side of the element. The pressure of compressed air must be less than 210 kPa (2.1 kgf/cm...

  • Page 51: Check Points Of Every 200 Hours

    5. Fill the engine oil until the specified level. IMPORTANT • To prevent serious damage to the engine, use only KUBOTA genuine filters or its equivalent. (1) Oil Filter Cartridge 9Y1210914GEG0022US0 Check of LPG / Natural Gas Tank Setting Condition 1.

  • Page 52: Check Points Of Every 500 Hours

    GENERAL WG1903-E3, WG2503-E3, WSM Check of Radiator Hoses and Clamp Bands 1. Make sure that the radiator hoses connections are correct for every 200 hours of operation or every 6 months, whichever comes first. 2. If the clamp is loose, apply oil to the threads and tighten it again correctly.
  • Page 53 GENERAL WG1903-E3, WG2503-E3, WSM Check of LPG / Natural Gas Lock Off Valve 1. Start the engine. 2. Make sure that an operation sound of solenoid is heard from the LPG / natural gas lock off valve (1). 3. Make sure that there is no fuel leakage from the LPG / natural gas lock off valve (1).

  • Page 54: Check Points Of Every 2000 Hours

    GENERAL WG1903-E3, WG2503-E3, WSM [8] CHECK POINTS OF EVERY 2000 HOURS Replacement of Spark Plug 1. Disconnect the ignition coil. 2. Remove the spark plug. 3. Replace the new spark plug. 4. Tighten the spark plug with a plug wrench.

  • Page 55: Check Points Of Every 1 Year

    GENERAL WG1903-E3, WG2503-E3, WSM [10] CHECK POINTS OF EVERY 1 YEAR Replacement of Air Cleaner Element 1. Remove the dust cup from the air cleaner. 2. After cleaning the dust cup, remove the air cleaner element. 3. Replace the new air cleaner element.
  • Page 56 GENERAL WG1903-E3, WG2503-E3, WSM Cleaning of Water Jacket and Radiator Interior CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen the cap slightly to release unwanted pressure before you remove the cap fully. 1. Stop the engine and let the coolant temperature decreases.
  • Page 57 GENERAL WG1903-E3, WG2503-E3, WSM Anti-freeze • There are 2 types of anti-freeze available: use the permanent type (PT) for this engine. • When you add anti-freeze for the first time, flush the water jacket and radiator interior with clean, soft water several times.

  • Page 58: Check Points Of Every 2 Years

    GENERAL WG1903-E3, WG2503-E3, WSM [11] CHECK POINTS OF EVERY 2 YEARS Replacement of Intake Air Line 1. Replace the intake hose and the clamps between the air cleaner and the electronic throttle body or gas mixer. 9Y1210914GEG0035US0 Replacement of Breather Hose 1.
  • Page 59 GENERAL WG1903-E3, WG2503-E3, WSM Replacement of Radiator Hoses and Clamp Bands CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen the cap to the stop to release unwanted pressure before you remove the cap fully.
  • Page 60 GENERAL WG1903-E3, WG2503-E3, WSM Change of Radiator Coolant (L.L.C.) CAUTION • Do not remove the radiator cap when the engine is hot. Then loosen the cap slightly to release unwanted pressure before you remove the cap fully. 1. Stop the engine and let the coolant temperature decreases.
  • Page 61 GENERAL WG1903-E3, WG2503-E3, WSM (Continued)  Anti-freeze • There are 2 types of anti-freeze available: use the permanent type (PT) for this engine. • When you add anti-freeze for the first time, flush the water jacket and radiator interior with clean, soft water several times.

  • Page 62: Special Tools

    GENERAL WG1903-E3, WG2503-E3, WSM 5. SPECIAL TOOLS Compression Tester Code No. • 07909-30251 Application • To measure the gasoline/LPG/natural gas engine compression and to make a decision for a large overhaul if necessary. 9Y1210914GEG0043US0 Oil Pressure Tester Code No. • 07916-32032 Application •...
  • Page 63 GENERAL WG1903-E3, WG2503-E3, WSM Bushing Replacing Tools Application • To press out and press fit the bushing. 1) For small end bushing 162 mm (6.38 in.) 35 mm (1.4 in.) 27 mm (1.1 in.) 35 mm dia. (1.4 in. dia.) 27.90 to 27.95 mm dia.
  • Page 64 GENERAL WG1903-E3, WG2503-E3, WSM Crankshaft Bearing 1 Replacing Tool Application • To press out and press fit the crankshaft bearing 1. [1] Extracting tool 135 mm (5.31 in.) 72 mm (2.8 in.) 40 mm radius (1.6 in. radius) 10 mm (0.39 in.) 20 mm (0.79 in.)
  • Page 65 GENERAL WG1903-E3, WG2503-E3, WSM Auxiliary Socket for Fixing Crankshaft Sleeve Application • To fix the crankshaft sleeve of the diesel engine. 80.0 mm (3.15 in.) 60.10 to 60.30 mm (2.367 to 2.374 in.) 80.0 mm dia. (3.15 in. dia.) 85.0 mm dia. (3.35 in. dia.) 60.10 to 60.30 mm dia.
  • Page 66 GENERAL WG1903-E3, WG2503-E3, WSM (Continued) Application • To fix the crankshaft sleeve of the diesel engine. 42.0 mm (1.65 in.) 30.50 to 30.60 mm (1.201 to 1.204 in.) 23.0 mm (0.906 in.) 20.0 mm (0.787 in.) 2.0 mm (0.079 in.) 31.911 to 31.950 mm dia.
  • Page 67 GENERAL WG1903-E3, WG2503-E3, WSM Bearing Case Cover Oil Seal Replacing Tool Application • To install bearing case cover oil seal. 42 mm dia. (1.7 in. dia.) 129 mm dia. (5.08 in. dia.) 32.000 to 32.025 mm dia. (1.2599 to 1.2608 in. dia.) 31.950 to 31.975 mm dia.
  • Page 68 ENGINE KiSC issued 05, 2019 A...
  • Page 69 MECHANISM CONTENTS 1. ENGINE BODY........................... 1-M1 [1] CRANKCASE ........................1-M1 [2] PCV VALVE.......................... 1-M1 [3] HALF-FLOATING HEAD COVER ..................1-M1 [4] POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM ..........1-M2 [5] CYLINDER HEAD ........................ 1-M2 [6] CRANKSHAFT ........................1-M2 [7] PISTON AND PISTON RING ....................1-M3 [8] CONNECTING ROD ......................
  • Page 70 (1) General ......................... 1-M24 (2) IC Regulator Built-in Type Alternator ................1-M24 [3] ENGINE CONTROL UNIT (ECU) ..................1-M27 [4] ENGINE COOLANT TEMPERATURE SENSOR ............... 1-M27 [5] TEMPERATURE AND MANIFOLD ABSOLUTE PRESSURE SENSOR (TMAP SENSOR) ........................... 1-M28 [6] CRANKSHAFT POSITION SENSOR ................. 1-M28 [7] CAMSHAFT POSITION SENSOR..................

  • Page 71: Engine Body

    ENGINE WG1903-E3, WG2503-E3, WSM 1. ENGINE BODY [1] CRANKCASE The engine has a high durability tunnel-type crankcase in which the crank bearing component is a constructed body. Furthermore, liner less type, allow effective cooling, less distortion, and greater wear resistance. The noise level is reduced to a minimum because each cylinder has its own chamber.

  • Page 72: Positive Crankcase Ventilation (Pcv) System

    ENGINE WG1903-E3, WG2503-E3, WSM [4] POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM During normal compression stroke, a small amount of gases in the combustion chamber escapes past the piston. Approximately 70 % of these blowby gases are unburned fuel (HC) that can dilute and contaminate the engine oil, cause corrosion to critical parts, and contribute to sludge build up.

  • Page 73: Piston And Piston Ring

    ENGINE WG1903-E3, WG2503-E3, WSM [7] PISTON AND PISTON RING Piston and Piston Ring The piston has a slightly oval shape when cold (in consideration of thermal expansion) and a concave head. Top Ring: The top ring is of plain barrel face type. The barrel...

  • Page 74: Rocker Arm Assembly

    ENGINE WG1903-E3, WG2503-E3, WSM [10] ROCKER ARM ASSEMBLY The rocker arm assembly includes the rocker arms (2) and adjusting screws (1), the end of which rests on the push rods, rocker arm brackets (4) and rocker arm shaft (3). rocker...

  • Page 75: Tappet Assembly (For Lm Model)

    ENGINE WG1903-E3, WG2503-E3, WSM [12] TAPPET ASSEMBLY (FOR LM MODEL) The tappet assembly is made up of a tappet and hydraulic lash adjuster (HLA). The tappet assembly converts cam rotation into linear reciprocating motion and receives cam force on the surface.

  • Page 76: Lubricating System

    • Full pressure feed type • Pressure feed and splash type KUBOTA engines have lubricating system of full pressure feed type. This system consists of an oil strainer (11), oil pump (12), relief valve (10), oil filter cartridge (9) and oil pressure switch (2).

  • Page 77: Oil Pump

    ENGINE WG1903-E3, WG2503-E3, WSM [2] OIL PUMP This oil pump has an inner rotor (1) and an outer rotor (2). The inner rotor (1), which is driven by crankshaft, rotates the outer rotor (2) in the same direction. The inner rotor (1) has one less lobe than the outer rotor (2), and they are eccentrically engaged with each other.

  • Page 78: Oil Cooler

    ENGINE WG1903-E3, WG2503-E3, WSM [5] OIL COOLER The engine is equipped with a water-cooled oil cooler to keep the temperature of the oil from rising while the engine is running and provide it with proper lubrication. The oil flows on the inside of the cooler plate and is cooled by the coolant flowing on the outside of the plate.

  • Page 79: Cooling System

    ENGINE WG1903-E3, WG2503-E3, WSM 3. COOLING SYSTEM [1] GENERAL (1) Radiator (2) Water Pump (3) Cooling Fan (4) Thermostat (5) Cylinder Head (6) Cylinder Block The cooling system consists of a radiator (1), a centrifugal water pump (2), a cooling fan (3) and a thermostat (4).

  • Page 80: Water Pump

    ENGINE WG1903-E3, WG2503-E3, WSM [2] WATER PUMP The water pump is driven by the crankshaft and a V belt. The rotating impeller (4) in the water pump sucks the coolant from the radiator and sends it into the water jacket in the cylinder block.

  • Page 81: Bottom Bypass System

    ENGINE WG1903-E3, WG2503-E3, WSM [4] BOTTOM BYPASS SYSTEM In addition to improving the cooling performance of the radiator by utilizing a bottom bypass system, the mechanism utilizes a 3-stage thermostat valve that reduces thermal shock considerably compared to previous radiators.

  • Page 82: Radiator Cap

    ENGINE WG1903-E3, WG2503-E3, WSM [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 in the radiator increases above the specified pressure, the pressure valve (1) opens to reduce the internal pressure.

  • Page 83: Fuel System

    ENGINE WG1903-E3, WG2503-E3, WSM 4. FUEL SYSTEM [1] GENERAL (1) Delivery Pipe (8) Vapor Hose* [A] Gasoline Fuel (c) Gaseous Propane or Natural (2) Fuel Pressure Manifold (FPM) (9) Vaporizer (DSR) [B] LPG / Natural Gas Fuel Gas Line* (3) Fuel Pump...

  • Page 84: Fuel Filter

    Outlet 9Y1210914ENM0056US0 [3] ELECTRONIC THROTTLE BODY (ETB) The Kubota fuel systems utilize Drive By Wire (DBW), to control engine speed, in this type of application. There is no direct connection between the operator pedal, and the throttle shaft. Speed and load...

  • Page 85: Fuel Pump

    ENGINE WG1903-E3, WG2503-E3, WSM [4] FUEL PUMP The gasoline system will use an external electric gasoline fuel pump. The pump will be mounted in the chassis of the vehicle, or equipment near the fuel tank. Gasoline rated fuel hose and securing devices supplied by the OEM, will be used to transfer the pumped fuel to the Gasoline Fuel Pressure Manifold assembly.

  • Page 86: Injectors And Delivery Pipe

    ENGINE WG1903-E3, WG2503-E3, WSM [6] INJECTORS AND DELIVERY PIPE The gasoline fuel delivery system, uses a delivery pipe (1) mounted with injectors (2), for each cylinder. The Engine Control Unit (ECU) will use the gasoline fuel delivery calibrations, to pulse width modulate each injector (2), to deliver the correct amount of gasoline, for optimized performance and emission control.

  • Page 87: Vaporizer (Dual Stage Regulator)

    ENGINE WG1903-E3, WG2503-E3, WSM [7] VAPORIZER (DUAL STAGE REGULATOR) When evaporating by primary chamber of vaporizer liquid propane or natural gas needs the evaporation heat. This vaporizer installs the water jacket, throws the coolant of engine, heats primary chamber, promotes evaporation.

  • Page 88: Lock Off Valve

    ENGINE WG1903-E3, WG2503-E3, WSM [8] LOCK OFF VALVE Vaporizer requires a normally-closed electrically controlled fuel lock off valve that is close coupled to the vaporizer and off when ignition switch is off or when the engine is not running normally. In operation without a lock off upstream the vaporizer will flow fuel with the engine off.

  • Page 89: Exhaust System

    KUBOTA engines have two kinds of catalytic devices, catalytic muffler and catalytic converter. (1) Catalytic Muffler (2) Catalytic Converter...

  • Page 90: Oxygen Sensor

    ENGINE WG1903-E3, WG2503-E3, WSM [2] OXYGEN SENSOR An Oxygen sensor is an essential element of a feedback control of air-fuel ratio. The sensor has a mechanism in which a zirconia tube, which is a solid electrolyte, is exposed into the exhaust gas and the...

  • Page 91: Electrical System

    ENGINE WG1903-E3, WG2503-E3, WSM 6. ELECTRICAL SYSTEM [1] STARTING SYSTEM (1) General The starting device consists of the starter, starter switch, fuse, battery etc., and the outline of the basic operation is as the followings; 1. Voltage from battery is added to the B terminal of starter switch through the fuse.
  • Page 92 ENGINE WG1903-E3, WG2503-E3, WSM When Pinion Gear Meshes with Ring Gear When the pinion gear (1) comes into mesh with the ring gear (4) on the flywheel and the magnetic switch is closed, a large current flows from the battery (7) directly into the field coil (2) and armature coil, but not through the pull-in coil (6).

  • Page 93: Starter Switch

    As the standard part of KUBOTA engine, the starter switch in below figure is recommended. [Connection Diagram] 9Y1210914ENM0038US0...

  • Page 94: Starter Safety System

    ENGINE WG1903-E3, WG2503-E3, WSM (4) Starter Safety System The ECU can be configured for either auto cranking (crank until starting) or crank limiting (maximum crank time and disabling of starter if frequency and number of tries is too high). 9Y1210914ENM0039US0...
  • Page 95 ENGINE WG1903-E3, WG2503-E3, WSM D2 Type Regulator (1) Alternator Assembly (2) IC Regulator (3) Key Switch IC regulator has a special feature that makes it possible to interrupt field current by using the transistor or IC instead of the contact-point-type regulator.
  • Page 96 ENGINE WG1903-E3, WG2503-E3, WSM Total Wave Rectification In case of the generator for mobile equipment of which purpose is to charge the batteries, alternating current cannot be used as it is. Because of this, it is required to conduct the action called rectification so that the alternating current can be changed to direct current.

  • Page 97: Engine Control Unit (Ecu)

    ENGINE WG1903-E3, WG2503-E3, WSM Surge voltage waveform with any charging cable disconnection. • May be VHmin = 6.5 V in high electric load shedding or unloaded condition with the battery fully charged. (1) Voltage (a) VH max (2) Angle of Rotation (°)

  • Page 98: Temperature And Manifold Absolute Pressure Sensor (Tmap Sensor)

    ENGINE WG1903-E3, WG2503-E3, WSM [5] TEMPERATURE AND MANIFOLD ABSOLUTE PRESSURE SENSOR (TMAP SENSOR) TMAP sensor is mounted in the intake manifold and measures the absolute pressure as well as the temperature of the air / fuel stream. MAP data is used by...

  • Page 99: Knock Sensor

    ENGINE WG1903-E3, WG2503-E3, WSM [8] KNOCK SENSOR The knock sensor is used to detect detonation through mechanical vibration in the engine block and / or cylinder heads and provide feedback for the ignition system to retard spark to reduce knock intensity. In most...
  • Page 100 SERVICING CONTENTS 1. TROUBLESHOOTING.........................1-S1 [1] FOR GENERAL ........................1-S1 [2] FOR GASOLINE FUEL ......................1-S2 [3] FOR LPG / NATURAL GAS FUEL ..................1-S2 2. SERVICING SPECIFICATIONS ....................1-S3 3. TIGHTENING TORQUES......................1-S10 [1] TIGHTENING TORQUES OF SCREWS, BOLTS AND NUTS FOR GENERAL USE..1-S10 [2] TIGHTENING TORQUES OF SCREWS, BOLTS AND NUTS FOR SPECIAL USE...1-S11 4.

  • Page 101: Troubleshooting

    ENGINE WG1903-E3, WG2503-E3, WSM 1. TROUBLESHOOTING [1] FOR GENERAL 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 – Starter malfunctioning Repair or replace...

  • Page 102: For Gasoline Fuel

    ENGINE WG1903-E3, WG2503-E3, WSM Reference Symptom Probable Cause Solution Page Exhaust Flames Damaged ignition coil Replace 1-S22 Damaged spark plug Adjust spark plug or G-13 replace Wires disconnected or damaged wire Reconnect / replace – Bad connection of ignition coil and spark plug Reconnect –...

  • Page 103: Servicing Specifications

    ENGINE WG1903-E3, WG2503-E3, WSM 2. SERVICING SPECIFICATIONS ENGINE BODY Item Factory Specification Allowable Limit Valve Clearance (Cold) (for Standard model) 0.18 to 0.22 mm – 0.0071 to 0.0086 in. Compression Pressure [WG1903] 1.55 MPa 1.24 MPa 15.8 kgf/cm 12.6 kgf/cm...
  • Page 104 ENGINE WG1903-E3, WG2503-E3, WSM Item Factory Specification Allowable Limit Valve Timing (Exhaust Valve) Open 0.70 rad – 40° before B.D.C. Close 0.21 rad – 12° after T.D.C. Valve Spring Free Length 41.7 to 42.2 mm 41.2 mm 1.65 to 1.66 in.
  • Page 105 ENGINE WG1903-E3, WG2503-E3, WSM Item Factory Specification Allowable Limit Camshaft Journal to Crankcase Bore Oil Clearance 0.050 to 0.091 mm 0.15 mm 0.0020 to 0.0035 in. 0.0059 in. • Camshaft Journal O.D. 39.934 to 39.950 mm – 1.5722 to 1.5728 in.
  • Page 106 ENGINE WG1903-E3, WG2503-E3, WSM Item Factory Specification Allowable Limit Crankpin to Crankpin Bearing Oil Clearance 0.025 to 0.087 mm 0.20 mm 0.00099 to 0.0034 in. 0.0079 in. • Crankpin O.D. 46.959 to 46.975 mm – 1.8488 to 1.8494 in. • Crankpin Bearing I.D.
  • Page 107 ENGINE WG1903-E3, WG2503-E3, WSM COOLING SYSTEM Item Factory Specification Allowable Limit Fan Belt Tension 10.0 to 12.0 mm / 98 N – 0.394 to 0.472 in. / 98 N (10 kgf, 22 lbf) Thermostat Opening- 69.5 to 72.5 °C –...
  • Page 108 ENGINE WG1903-E3, WG2503-E3, WSM IGNITION SYSTEM Item Factory Specification Allowable Limit Ignition Timing [WG1903] Gasoline Fuel 0.52 rad (30°) – before T.D.C. / 2700 min (rpm) 0.14 rad (8°) – before T.D.C. / 900 min (rpm) LPG Fuel 0.47 rad (27°) –...
  • Page 109 ENGINE WG1903-E3, WG2503-E3, WSM Item Factory Specification Allowable Limit Spark Plug Plug Gap 0.70 to 0.80 mm – (NGK: IFR6F8DN) 0.028 to 0.031 in. Resistance of Ignition Coil Primary (+) - (−) 0.63 to 0.77 Ω – at 25 °C (77 °F) Secondary Side 7.29 to 8.91 kΩ...

  • Page 110: Tightening Torques

    ENGINE WG1903-E3, WG2503-E3, WSM 3. TIGHTENING TORQUES Use a torque wrench to tighten the screws, bolts and nuts to the specified torque. Tighten the screws, bolts and nuts used, such as on the cylinder head in the correct sequence and torque.

  • Page 111: Tightening Torques Of Screws, Bolts And Nuts For Special Use

    ENGINE WG1903-E3, WG2503-E3, WSM [2] TIGHTENING TORQUES OF SCREWS, BOLTS AND NUTS FOR SPECIAL USE NOTE • For the screws, bolts and nuts with the mark "*", apply engine oil to their threads and seats before you tighten. • The alphabet "M" in Dimension × Pitch shows that the screw, bolt or nut dimensions are in the metric system.
  • Page 112 ENGINE WG1903-E3, WG2503-E3, WSM Dimension × Item N·m kgf·m lbf·ft Pitch Lockoff valve fitting union PT 1/4 11.2 to 12.8 1.15 to 1.30 8.26 to 9.44 9Y1210914ENS0006US0 1-S12 KiSC issued 05, 2019 A...

  • Page 113: Checking, Disassembling And Servicing

    ENGINE WG1903-E3, WG2503-E3, WSM 4. CHECKING, DISASSEMBLING AND SERVICING [1] CHECKING AND ADJUSTING (1) Engine Body Compression Pressure 1. Operate the engine for warming-up. 2. Stop the engine. 3. Remove the air cleaner, the muffler and all spark plugs. 4. Set a compression tester with the adaptor to the spark plug hole.
  • Page 114 ENGINE WG1903-E3, WG2503-E3, WSM Adjusting Valve Clearance (for LM model) IMPORTANT • You must examine and adjust the valve clearance when the engine is cold. 1. Remove the head cover. 2. Align the "1TC" mark line (1) on the flywheel and alignment mark (2) on the housing.
  • Page 115 ENGINE WG1903-E3, WG2503-E3, WSM Check of Tappet Assembly 1. Push the hydraulic lash adjuster (HLA) (1) with finger from top. 2. If the HLA (1) does not move, it is OK. If the HLA (1) move, do the work after step.

  • Page 116: Lubricating System

    ENGINE WG1903-E3, WG2503-E3, WSM (2) Lubricating System Engine Oil Pressure 1. Remove the engine oil pressure switch, and set the oil pressure tester. 2. Operate the engine for warming-up. 3. Measure the oil pressure at the idle speed and rated speed.
  • Page 117 ENGINE WG1903-E3, WG2503-E3, WSM Fan Belt Damage and Wear 1. Examine the fan belt for damage. 2. If the fan belt has a damage, replace it. 3. Examine if the fan belt is worn out and sunk in the pulley groove.

  • Page 118: Fuel System

    ENGINE WG1903-E3, WG2503-E3, WSM Opening-temperature of Thermostat Valve 1. Hang the thermostat in the water by a string with its end put between the valve and the seat. 2. Increase the temperature of the water gradually, read the temperature when the valve opens and disconnects the string.
  • Page 119 ENGINE WG1903-E3, WG2503-E3, WSM Resistance of Fuel Pressure Manifold (FPM) 1. Disconnect the connector. 2. Measure the resistance between terminal 1 and terminal 2 with an ohmmeter. 3. If the resistance is not with in the factory specifications, replace Factory Terminal 1 –...
  • Page 120 NOTE • The LPG / natural gas 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. • Vapor hose length must not exceed 700 mm (27.6 in), shorter is generally considered better.

  • Page 121: Ignition System

    ENGINE WG1903-E3, WG2503-E3, WSM (5) Ignition System Resistance of Crankshaft Position Sensor / Camshaft Position Sensor 1. Disconnect the connector. 2. Measure the resistance with an ohmmeter. 3. If the resistance is not with in the factory specifications, replace 1.85 to 2.45 kΩ...
  • Page 122 ENGINE WG1903-E3, WG2503-E3, WSM Spark Plug Gap 1. Remove the spark plug, and remove carbon from the electrode with a wire brush or other tools. 2. Measure the spark plug gap with a feeler gauge, and repair or replace the plug if the measured gap differs from the factory specification.

  • Page 123: Electrical System

    ENGINE WG1903-E3, WG2503-E3, WSM (6) Electrical System CAUTION • To prevent an accidental short circuit, attach the positive cable to the positive terminal before the negative cable is attached to the negative terminal. • Do not remove the battery cap while the engine operates.
  • Page 124 ENGINE WG1903-E3, WG2503-E3, WSM Battery Specific Gravity CAUTION • If battery acid (dilute sulfuric acid) gets on you it could cause blindness or burns, or could cause corrosion of machinery and tools so please be careful when handling. • Wear safety glasses and rubber gloves when performing battery maintenance and inspection (measuring specific gravity, replenishing water, or charging).
  • Page 125 ENGINE WG1903-E3, WG2503-E3, WSM Motor Test CAUTION • Hold the starter to prevent its movement when you do a test on the motor. 1. Disconnect the negative cable from the battery. 2. Disconnect the positive cable from the battery. 3. Disconnect the leads from the starter B terminal.
  • Page 126 ENGINE WG1903-E3, WG2503-E3, WSM Alternator-on Unit Test Before testing • Before the alternator-on unit test, do a check of the list below: – Battery terminal connections – Circuit connection – Fan belt tension – Charge indicator lamp – Fuses on the circuit –...

  • Page 127: Disassembling And Assembling

    ENGINE WG1903-E3, WG2503-E3, WSM [2] DISASSEMBLING AND ASSEMBLING IMPORTANT • When reassembling, replace all of the O-rings and gaskets by new ones. • When disassembling the LPG / natural gas engine after completely consuming the fuel in piping. • In order to reduce the fuel pressure, do not remove the fuel hose at least 3 minutes after stopping the engine.

  • Page 128: External Components

    ENGINE WG1903-E3, WG2503-E3, WSM (2) External Components Alternator, Starter and Others (for Standard model) 1. Remove the air cleaner and muffler and exhaust manifold (4). 2. Remove the cooling fan (1), fan belt (2), alternator (3) and starter (5). (When reassembling) •...
  • Page 129 ENGINE WG1903-E3, WG2503-E3, WSM Vapor Hose and Coolant Hose CAUTION • Close the LPG / natural gas tank valve. • In order to reduce the fuel pressure, do not remove the fuel hose at least 3 minutes after stopping the engine.

  • Page 130: Cylinder Head, Valves And Oil Pan

    ENGINE WG1903-E3, WG2503-E3, WSM Ignition Coil and Spark Plug 1. Disconnect the ignition coil connector (1). 2. Remove the ignition coil (2). 3. Remove the spark plug (3). (When reassembling) • Tighten the spark plug with a plug wrench. NOTE (When reassembling) •...
  • Page 131 ENGINE WG1903-E3, WG2503-E3, WSM Rocker Arm and Push Rods (for Standard Model) 1. Remove the screws of the rocker arm bracket. 2. Remove the rocker arm assembly (1). 3. Remove the push rods (2). (When reassembling) • When you put the push rods (2) on the tappets (3), make sure that their ends are correctly engaged with the grooves.
  • Page 132 ENGINE WG1903-E3, WG2503-E3, WSM Rocker Arm and Push Rods (for LM Model) 1. Remove the screws of the rocker arm bracket. 2. Remove the rocker arm assembly (2). 3. Remove the push rods (1). (When reassembling) • When installing the push rods (1), mount it securely contact to the HLA (3).
  • Page 133 ENGINE WG1903-E3, WG2503-E3, WSM Cylinder Head 1. Loosen the pipe clamps (2), and remove the water return hose (1). 2. Remove the spark plug. 3. Remove the cylinder head screw in the sequence of (n or r) to (a). 4. Remove the ignition coil flange and flange gasket.
  • Page 134 ENGINE WG1903-E3, WG2503-E3, WSM Tappets / Tappet Assemblies 1. Remove the tappets (1) / tappet assemblies (2) from the crankcase. (When reassembling) • Before you install the tappets (1) / tappet assemblies (2), apply a thin layer of engine oil around them.
  • Page 135 ENGINE WG1903-E3, WG2503-E3, WSM Oil Cooler (If Necessary) 1. Remove the water pipe (1). 2. Remove the oil filter cartridge (2). 3. Remove the oil cooler joint screw (4). 4. Remove the oil cooler (3). (When reassembling) • When mounting the oil cooler (3), take care not to forget mounting the O-ring and not to let it out of position.

  • Page 136: Thermostat

    ENGINE WG1903-E3, WG2503-E3, WSM Oil Pan and Oil Strainer 1. Remove the oil pan mounting screws (2) and oil pan (1). 2. Remove the oil strainer (3) and O-ring (4). (When reassembling) • After you clean the oil strainer (3), make sure that the filter mesh is clean and install it.

  • Page 137: Gear Case And Timing Gears

    ENGINE WG1903-E3, WG2503-E3, WSM Water Pump Assembly (If Necessary) 1. Remove the water pump assembly (1) from the gear case. (When reassembling) • Replace the gasket (2) with a new one. (1) Water Pump Assembly (2) Gasket 9Y1210914ENS0045US0 (5) Gear Case and Timing Gears Fan Drive Pulley 1.
  • Page 138 ENGINE WG1903-E3, WG2503-E3, WSM Crankshaft Oil Slinger 1. Remove the crankshaft collar (5). 2. Remove the O-ring (4). 3. Remove the crankshaft oil slinger (3). 4. Remove the oil pump drive gear (1) and the rotor gear (2). (When reassembling) •...

  • Page 139: Piston And Connecting Rod

    ENGINE WG1903-E3, WG2503-E3, WSM (6) Piston and Connecting Rod Connecting Rod Cap 1. Remove the connecting rod cap (1). (When reassembling) • Align the marks (a) with each other. (Face the marks toward the intake manifold.) • Apply engine oil to the connecting rod screws and lightly screw it in by hand, then tighten it to the specified torque.

  • Page 140: Crankshaft

    ENGINE WG1903-E3, WG2503-E3, WSM Piston Ring and Connecting Rod 1. Remove the piston rings (1), (2), (3) and (4) with a piston ring tool. 2. Remove the piston pin (10) to disconnect the connecting rod (8) from the piston (7).
  • Page 141 ENGINE WG1903-E3, WG2503-E3, WSM Bearing Case Cover 1. Remove the mounting screws of the bearing case cover. First, remove inner screws (5) and then external screws (3). 2. Remove the bearing case cover (6). IMPORTANT • The length of inner screws (5) and external screws (3) are different.
  • Page 142 ENGINE WG1903-E3, WG2503-E3, WSM Crankshaft Assembly (for 3 Cylinders) NOTE • Before you disassemble, measure the side clearance of crankshaft. Measure it when you assemble again. 1. Remove the screw 2 (1) of the main bearing case. 2. Turn the crankshaft to set the crankpin of the third cylinder to the bottom dead center.
  • Page 143 ENGINE WG1903-E3, WG2503-E3, WSM Crankshaft Assembly (for 4 cylinders) NOTE • Before you disassemble, measure the side clearance of crankshaft. Measure it when you assemble again. 1. Remove the screw 2 (1) of the main bearing case. 2. Turn the crankshaft to set the crankpin of the fourth cylinder to the horizontal directions (right or left).
  • Page 144 ENGINE WG1903-E3, WG2503-E3, WSM Main Bearing Case Assembly 1. Remove the screws 1 of the main bearing case (7). Then remove the main bearing case. 2. Remove other main bearing cases as above. (When reassembling) • Clean the oil channel in the main bearing case.

  • Page 145: Starter

    ENGINE WG1903-E3, WG2503-E3, WSM (8) Starter Starter (1) Through Bolt (2) Brush (3) C Terminal Nut (4) Yoke (5) Armature (6) Overrunning Clutch (7) Idle Gear (8) End Frame (9) Brush Holder (10) Magnet Switch Cover (11) Plunger (12) B Terminal Nut (13) Housing 1.

  • Page 146: Alternator

    ENGINE WG1903-E3, WG2503-E3, WSM (9) Alternator Alternator (1) Pulley (2) Drive End Frame (3) Stator (4) Bearing (5) Retainer Plate (6) Rotor (7) Bearing (8) Rear End Frame (9) Rectifier (10) IC Regulator (11) Brush Holder (12) Rear End Cover 1.

  • Page 147: Servicing

    ENGINE WG1903-E3, WG2503-E3, WSM [3] SERVICING (1) Cylinder Head and Valves Top Clearance 1. Remove the cylinder head. 2. With the piston at TDC, use grease to affix three or four plastigauges (1) of a diameter 1.5 mm (0.059 in.) × 5.0 to 7.0 mm (0.20 to 0.27 in.) long to the crown of the piston;...

  • Page 148: Valve Recessing

    ENGINE WG1903-E3, WG2503-E3, WSM Cylinder Head Flaw 1. Prepare an air spray red check. 2. Clean the surface of the cylinder head with detergent (2). 3. Apply some red permeative liquid (1) on the cylinder head surface. After you apply, do not touch it for 5 to 10 minutes.
  • Page 149 ENGINE WG1903-E3, WG2503-E3, WSM Valve Lapping 1. Apply the compound equally to the valve lapping surface. 2. Put the valve into the valve guide. Lap the valve on its seat with a valve lapping tool. 3. After you lap the valve, clean away the compound and apply oil, then lap the valve again with oil.
  • Page 150 ENGINE WG1903-E3, WG2503-E3, WSM Replacement of Valve Guide (When removing) 1. Press out the used valve guide with the valve guide replacing tool. (See page "SPECIAL TOOLS".) (When installing) 1. Clean the new valve guide and valve guide bore, and apply engine oil to them.
  • Page 151 ENGINE WG1903-E3, WG2503-E3, WSM Free Length and Tilt of Valve Spring 1. Measure the free length (B) of valve spring with a vernier calipers. 2. If the measurement is less than the allowable limit, replace it. 3. Put the valve spring on a surface plate, and put a square on the side of the valve spring.
  • Page 152 ENGINE WG1903-E3, WG2503-E3, WSM Push Rod Bend 1. Put the push rod on V blocks. 2. Set a dial indicator with its point on the middle of the push rod. 3. Turn the push rod slowly and read the variation on the indicator.

  • Page 153: Timing Gear And Camshaft

    ENGINE WG1903-E3, WG2503-E3, WSM (2) Timing Gear and Camshaft Timing Gear Backlash 1. Set a dial indicator (lever type) with its point on the gear tooth. 2. Hold the mating gear and move the gear to measure the backlash. 3. If the backlash is more than the allowable limit, measure the oil clearance in the journal part of each shaft.
  • Page 154 ENGINE WG1903-E3, WG2503-E3, WSM Cam Height 1. Measure the height of the cam at its highest point with an external micrometer. 2. If the measurement is less than the allowable limit, replace the camshaft. 33.90 mm Factory specification 1.335 in.

  • Page 155: Piston And Connecting Rod

    ENGINE WG1903-E3, WG2503-E3, WSM Replacement of Idle Gear Bushing (When removing) 1. Press out the used idle gear bushing with the replacing tool. (See page "SPECIAL TOOLS".) (When installing) 1. Clean a new idle gear bushing and idle gear bore, and apply engine oil to them.
  • Page 156 ENGINE WG1903-E3, WG2503-E3, WSM Piston Ring Gap 1. Put the piston ring into the lower part of the liner (the least worn out part) with the piston. 2. Measure the ring gap with a feeler gauge. 3. If the ring gap is more than the allowable limit, replace the ring.

  • Page 157: Connecting Rod Alignment

    ENGINE WG1903-E3, WG2503-E3, WSM Connecting Rod Alignment NOTE • Make sure that the oil clearance of the small end bushing is less than the allowable limit. 1. Install the piston pin into the connecting rod. 2. Install the connecting rod on the alignment tool of the connecting rod.
  • Page 158 ENGINE WG1903-E3, WG2503-E3, WSM Oil Clearance between Crankpin and Crankpin Bearing 1. Clean the crankpin and crankpin bearing. 2. Put a strip of plastigauge 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 159 ENGINE WG1903-E3, WG2503-E3, WSM Oil Clearance between Crankshaft Journal and Crankshaft Bearing 1 1. Measure the O.D. of the crankshaft journal with an external micrometer. 2. Measure the I.D. of the crankshaft bearing 1 with an internal micrometer. 3. Calculate the oil clearance.
  • Page 160 ENGINE WG1903-E3, WG2503-E3, WSM Oil Clearance between Crankshaft Journal and Crankshaft Bearing 2 1. Put a strip of plastigauge on the center of the journal. 2. Install the bearing case and tighten the baring case screws 1 to the specified torque, and remove the bearing case again.
  • Page 161 ENGINE WG1903-E3, WG2503-E3, WSM Replacement of Crankshaft Sleeve 1. Remove the used crankshaft sleeve (3). 2. Set the sleeve guide (2) to the crankshaft (5). 3. Set the stopper (1) to the crankshaft (5) (see the figure). 4. Increase the temperature of a new sleeve to between 150 and 200 °C (302 and 392 °F).

  • Page 162: Cylinder

    ENGINE WG1903-E3, WG2503-E3, WSM (5) Cylinder Cylinder Wear 1. Measure the I.D. of the cylinder at the 6 positions (see figure) with a cylinder gauge. 2. Find the maximum and minimum inner diameters. 3. Find the difference between the maximum and the minimum inner diameters.

  • Page 163: Oil Pump

    ENGINE WG1903-E3, WG2503-E3, WSM (6) Oil Pump Rotor Lobe Clearance 1. Measure the clearance between the lobes of the inner rotor and the outer rotor with a feeler gauge. 2. Measure the clearance between the outer rotor and the pump body with a feeler gauge.

  • Page 164: Brush Holder

    ENGINE WG1903-E3, WG2503-E3, WSM Commutator and Mica 1. Examine the contact of the commutator for wear, and grind the commutator with emery paper if it is lightly worn. 2. Measure the commutator O.D. with an external micrometer at some points.

  • Page 165: Armature Coil

    ENGINE WG1903-E3, WG2503-E3, WSM Armature Coil 1. Examine the continuity across the commutator and armature coil core with the resistance range of circuit tester. 2. If electricity flows, replace the armature assembly. 3. Examine the continuity across the segments of the commutator with the resistance range of circuit tester.
  • Page 166 ENGINE WG1903-E3, WG2503-E3, WSM Stator 1. Measure the resistance across each lead of the stator coil with the resistance range of circuit tester. 2. If the measurement is not in the factory specification, replace the stator assembly. 3. Examine the continuity across each stator coil lead and core with the resistance range of circuit tester.
  • Page 167 ENGINE WG1903-E3, WG2503-E3, WSM Rectifier 1. Examine the continuity across each diode of rectifier with the resistance range of circuit tester. 2. The rectifier is correct if the diode in the rectifier conducts electricity only in one direction. 9Y1210914ENS0113US0 IC Regulator 1.
  • Page 168 Editor : Engine Service Department Address 64, Ishizu-Kitamachi, Sakai-Ku, Sakai-City, Osaka, 590-0823, Japan Phone +81- 72-241-1531 +81- 72-245-2928 E-mail : kbt_g.estg-pub@kubota.com Printed in Japan 2019. 05, S, EI, EI, engusa Code No.9Y111-09147 2013. 09, S, EI, EI, engusa KUBOTA Corporation...

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