Page 1 WORKSHOP MANUAL ZERO TURN MOWER ZD321,ZD326,ZD331 KiSC issued 04, 2007 A...
Page 2 The right is reserved to make changes in all information at any time without notice. Due to covering many models of this manual, information or picture being used have not been specified as one model. December 2006 © KUBOTA Corporation 2006 KiSC issued 04, 2007 A...
Page 3 ZD321, ZD326, ZD331, 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 warn of the possibility of personal injury. Read these instructions carefully. It is essential that you read the instructions and safety regulations before you attempt to repair or use this unit.
Page 4 ZD321, ZD326, ZD331, 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 ZD321, ZD326, ZD331, WSM SAFETY INSTRUCTIONS VENTILATE WORK AREA • If the engine must be running to do some 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 ZD321, ZD326, ZD331, WSM SAFETY INSTRUCTIONS SAFETY DECALS The following safety decals are installed on the machine. If a decal becomes damaged, illegible or is not on the machine, replace it. The decal part number is listed in the parts list. KiSC issued 04, 2007 A...
Page 7 ZD321, ZD326, ZD331, WSM SAFETY INSTRUCTIONS KiSC issued 04, 2007 A...
Page 8 ZD321, ZD326, ZD331, WSM SAFETY INSTRUCTIONS KiSC issued 04, 2007 A...
Page 9 ZD321, ZD326, ZD331, WSM SAFETY INSTRUCTIONS KiSC issued 04, 2007 A...
Page 10 ZD321, ZD326, ZD331, WSM SPECIFICATIONS SPECIFICATIONS Model ZD321N ZD321 ZD326S ZD326P ZD331P ZD331LP Model D782-E2-ZD D1005-E2-ZD-2 D1305-E3-ZD Maximum engine power 15.7 kW (21 HP) 19.4 kW (26 HP) 23.1 kW (31 HP) (Gross) Type Liquid-cooled Number of cylinders 67 x 73.6 mm 76 x 73.6 mm 78 x 88.0 mm Bore and stroke...
Page 11 1 speed (2538 rpm at 3000 Revolution 1 speed (2530 rpm at 3200 engine rpm) engine rpm) Drive system Shaft drive, KUBOTA 10 tooth in involute spline Clutch type Wet multi discs PTO brake Wet single disc NOTE: Specifications and design subject to change without notice.
Page 12 ZD321, ZD326, ZD331, WSM DIMENSIONS DIMENSIONS KiSC issued 04, 2007 A...
Page 13 GENERAL KiSC issued 04, 2007 A...
Page 14: Table Of Contents
GENERAL CONTENTS 1. IDENTIFICATION..................... G-1 2. GENERAL PRECAUTIONS ................G-2 3. HANDLING PRECAUTIONS FOR ELECTRICAL PARTS AND WIRING .. G-3 [1] WIRING...................... G-3 [2] BATTERY....................G-5 [3] FUSE......................G-5 [4] CONNECTOR .................... G-5 [5] HANDLING OF CIRCUIT TESTER............G-6 4. LUBRICANTS, FUEL AND COOLANT ............G-7 5.
Page 15: Identification
ZD321, ZD326, ZD331, WSM G GENERAL 1. IDENTIFICATION When contacting your local KUBOTA distributor, always specify engine serial number (3), machine serial number (2), mower serial number (4) and hour meter reading. (1) Machine Identification Plate (4) Mower Serial Number...
Page 16: General Precautions
Screws, bolts and nuts should be installed 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 17: Handling Precautions For Electrical Parts And Wiring
ZD321, ZD326, ZD331, WSM G GENERAL 3. HANDLING PRECAUTIONS FOR ELECTRICAL PARTS AND WIRING To ensure safety and prevent damage to the machine and surrounding equipment, heed the following precautions in handling electrical parts and wiring. IMPORTANT • Check electrical wiring damage loosened...
Page 18 ZD321, ZD326, ZD331, WSM G GENERAL • Securely clamp, being careful not to damage wiring. (1) Clamp (3) Clamp • Wind Clamp Spirally (4) Welding Dent (2) Wire Harness W1011458 • Clamp wiring so that there is no twist, unnecessary sag, or excessive tension, except for movable part, where sag be required.
Page 19: Battery
ZD321, ZD326, ZD331, WSM G GENERAL [2] BATTERY • Take care not to confuse positive and negative terminal posts. • When removing battery cables, disconnect negative cable first. When installing battery cables, check for polarity and connect positive cable first. •...
Page 20: Handling Of Circuit Tester
ZD321, ZD326, ZD331, WSM G GENERAL • Use sandpaper to remove rust from terminals. • Repair deformed terminal. Make certain there is no terminal being exposed or displaced. (1) Exposed Terminal (3) Sandpaper (2) Bend Terminal (4) Rust W1012346 • Make certain that there is no female connector being too open. (A) Correct (B) Incorrect W1012430...
Page 21: Lubricants, Fuel And Coolant
• * Oil amount when the oil level is the upper of the oil level gauge. • ** KUBOTA original transmission hydraulic fluid. IMPORTANT • To prevent serious damage to hydraulic system, use only KUBOTA genuine fluid or its equivalent. KiSC issued 04, 2007 A...
Page 22 ZD321, ZD326, ZD331, WSM G GENERAL Greasing, oiling (Machine) Place No. of greasing point Capacity Type of grease Motion control lever pivot bushing and contact position Center pin SAE multi-purpose type grease King pin Until grease overflows NLG1-2 or NLG1-1 Front wheel (GC-LB) Front lift arm...
Page 23: Tightening Torques
ZD321, ZD326, ZD331, WSM G GENERAL 5. TIGHTENING TORQUES [1] GENERAL USE SCREWS, BOLTS AND NUTS Screws, bolts, and nuts whose tightening torques are not specified in this Workshop Manual should be tightened according to the table below. Indication on top of No-grade or 4T bolt SCr435,...
Page 24: Metric Screws, Bolts And Nuts
ZD321, ZD326, ZD331, WSM G GENERAL [3] METRIC SCREWS, BOLTS AND NUTS Property class 8.8 Property class 10.9 Grade Unit Nominal N·m kgf·m lbf·ft N·m kgf·m lbf·ft Diameter 24 to 27 2.4 to 2.8 18 to 20 30 to 34 3.0 to 3.5 22 to 25 48 to 55...
Page 25: Maintenance Check List
ZD321, ZD326, ZD331, WSM G GENERAL 6. MAINTENANCE CHECK LIST Service interval Period Refe- rence After 100 150 200 250 300 350 400 450 500 550 600 Items page since every Engine oil Change G-17 100 Hr every Engine oil filter Replace G-17 200 Hr...
Page 26 *1 This maintenance should be done daily more often in dusty condition than in normal conditions. Suggested cleaning interval is every 100 hours in normal conditions. *2 These items should be serviced by an authorized KUBOTA Dealer, unless the owner has the proper tools and is mechanically proficient.
Page 27: Check And Maintenance
ZD321, ZD326, ZD331, WSM G GENERAL 7. CHECK AND MAINTENANCE CAUTION • Be sure to check and service the machine on a flat place with engine shut off, the parking brake on and chock the wheels. [1] DAILY CHECK To prevent trouble from occurring, it is important to know the condition of the machine. Check the following items before starting.
Page 28 ZD321, ZD326, ZD331, WSM G GENERAL Checking Tire Pressure WARNING To avoid personal injury: • Do not attempt to mount a tire on a rim. This should be done by a qualified person with the proper equipment. • Always maintain the correct tire pressure. Inflation pressure in front tires rises quickly when using compressed air.
Page 29 ZD321, ZD326, ZD331, WSM G GENERAL Checking Coolant Level CAUTION To avoid personal injury: • 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. Check the coolant level daily both the radiator and the recovery tank before staring engine.
Page 30 ZD321, ZD326, ZD331, WSM G GENERAL Checking and Cleaning Radiator to Prevent Overheating CAUTION To avoid personal injury: • Be sure to stop the engine and remove the key before cleaning. IMPORTANT • The air intake area must be clear of debris to prevent the engine from overheating.
Page 31: Check Points Of Initial 50 Hours
IMPORTANT • To prevent serious damage to the engine, element of recommended type must be used. Use only a genuine KUBOTA filter or its equivalent. (1) Engine Oil Filter Cartridge W1030949 KiSC issued 04, 2007 A G-17...
Page 32 Add fluid to proper level. Check for oil leaks around filter gasket. IMPORTANT • To prevent serious damage or premature failure to the hydraulic system, use only a KUBOTA genuine filter. (1) HST Transmission Oil Filter Cartridge W1031068...
Page 33: Check Point Of Initial 100 Hours
ZD321, ZD326, ZD331, WSM G GENERAL [3] CHECK POINT OF INITIAL 100 HOURS Adjusting Front Axle Pivot 1. Lift up and securely block the front of the machine. 2. Measure the clearance (A) between the front axle (4) and front axle support (3).
Page 34: Check Point Of Initial 400 Hours
ZD321, ZD326, ZD331, WSM G GENERAL [4] CHECK POINT OF INITIAL 400 HOURS Changing Transmission Fluid and Rear Axle Gear Case Oil (RH and LH) CAUTION To avoid personal injury: • Be sure to stop the engine and remove the key before changing or checking the oil.
Page 35: Check Points Of Every 50 Hours
ZD321, ZD326, ZD331, WSM G GENERAL [5] CHECK POINTS OF EVERY 50 HOURS Checking Safety Device CAUTION To avoid personal injury: • Do not allow anyone near the machine while testing. • If the machine does not pass one of the following tests, do not operate the machine.
Page 36 ZD321, ZD326, ZD331, WSM G GENERAL Test 6 (OPERATOR ON THE SEAT) 1. Start the engine. 2. Do not set the parking brake. 3. Shift the PTO lever (4) to “DISENGAGE” (OFF) position. 4. Grasp the motion control levers (2) and move then inward from “NEUTRAL LOCK”...
Page 37 ZD321, ZD326, ZD331, WSM G GENERAL Greasing 1. Apply a grease to the following position as figures. CAUTION To avoid personal injury: • Be sure to stop the engine and remove the key before greasing. (1) King Pin (LH · RH) (4) Motion Control Lever Pivot Bushing (2) Center Pin (LH ·...
Page 38 ZD321, ZD326, ZD331, WSM G GENERAL Greasing (Continued) 1. Apply a grease to the following position as figures. CAUTION To avoid personal injury: • Be sure to stop the engine and remove the key before greasing. (1) Seat Adjuster [A] ZD321 (2) Throttle Cable (Oil) [B] ZD326, ZD331 W1035206...
Page 39: Check Points Of Every 100 Hours
ZD321, ZD326, ZD331, WSM G GENERAL Checking Gear Box Oil Level CAUTION To avoid personal injury: • Always stop the engine and remove the key before checking oil. 1. Park the machine on a flat surface and lower the mower to the ground.
Page 40 ZD321, ZD326, ZD331, WSM G GENERAL Battery Charging DANGER To avoid serious injury or death: • When the battery is being activated, hydrogen and oxygen gases in the battery are extremely explosive. Keep open sparks and flames away from the battery at all times, especially when charging the battery.
Page 41 ZD321, ZD326, ZD331, WSM G GENERAL Checking Fuel Lines and Fuel Filter CAUTION • Be sure to stop the engine and remove the key when attempting to make the following checks and changes. • Never fail to check the fuel lines periodically. The fuel lines are subject to wear and age.
Page 42 ZD321, ZD326, ZD331, WSM G GENERAL Checking Parking Brake CAUTION To avoid personal injury: • Park the machine on a hard and level surface. • Stop the engine and chock the wheels before checking or adjusting. IMPORTANT • Wrong adjustment may cause machine damage. Check brake spring 1.
Page 43: Check Points Of Every 150 Hours
ZD321, ZD326, ZD331, WSM G GENERAL Check on the slope 1. Place the machine on a 17° ramp. 2. Apply the parking brake. 3. Place the motion control levers in “NEUTRAL LOCK” position and shut off the engine. 4. Check that the machine does not move. NOTE •...
Page 44 ZD321, ZD326, ZD331, WSM G GENERAL Checking Hydraulic Hose CAUTION To avoid personal injury: • Be sure to stop the engine and remove the key before checking and replacing hydraulic hose. • Allow transmission case to cool down sufficiently; oil can be hot and may cause burns.
Page 45: Check Point Of Every 400 Hours
ZD321, ZD326, ZD331, WSM G GENERAL [9] CHECK POINT OF EVERY 400 HOURS Replacing Fuel Filter 1. See page G-27. W1040109 Replacing Transmission Oil Filter Cartridge 1. See page G-18. W1061793 Changing Transmission Fluid and Rear Axle Gear Case Oil (RH and LH) 1.
Page 46 ZD321, ZD326, ZD331, WSM G GENERAL Flushing Cooling System and Changing Coolant 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. 1.
Page 47 ZD321, ZD326, ZD331, WSM G GENERAL Flushing Cooling System and Changing Coolant (Continued) Anti-Freeze If coolant freezes, the cylinders and radiator can be damaged. It is necessary, if the ambient temperature falls below 0 °C (32 °F), to remove coolant mix it with anti-freeze and full the radiator with 1.
Page 48: Check Point Of Every 2 Years
ZD321, ZD326, ZD331, WSM G GENERAL [11] CHECK POINT OF EVERY 2 YEARS Replacing Hydraulic Hose 1. Replace the hose. Refer to “Checking Hydraulic Hose”. (See page G-30.) W1067327 Replacing Radiator Hose 1. Replace the hoses and clamps. Refer to “Checking Radiator Hose and Hose Clamp”. (See page G-29.) W1067436 Replacing Fuel Lines...
Page 49: Others
ZD321, ZD326, ZD331, WSM G GENERAL [12] OTHERS Replacing Fuses 1. The electrical system is protected from potential damage by fuses. A blown fuse indicates that there is an overload or short somewhere in the electrical system. 2. If any of the fuses should blow, replace with a new one of the same capacity.
Page 50 ZD321, ZD326, ZD331, WSM G GENERAL Checking Mower Blade and Replacing Mower Blade 1. Check the cutting edge of mower blade. 2. Sharpen the cutting edges, if the mower blades are as shown in figure (2). 3. Replace the mower blades, if they are as shown in figure (3). NOTE •...
Page 51: Special Tools
ZD321, ZD326, ZD331, WSM G GENERAL 8. SPECIAL TOOLS [1] SPECIAL TOOLS FOR ENGINE Special Use Puller Set Code No.: 07916-09032 Application: Use exclusively for pulling out bearing, gears and other parts with ease. W10520950 Piston Ring Compressor Code No.: 07909-32111 Application: Use exclusively for pushing in the piston with piston rings into the cylinder.
Page 52 ZD321, ZD326, ZD331, WSM G GENERAL Oil Pressure Tester Code No.: 07916-32032 Application: Use to measure lubricating oil pressure. (1) Gauge (5) Adaptor 2 (2) Cable (6) Adaptor 3 (3) Threaded Joint (7) Adaptor 4 (4) Adaptor 1 (8) Adaptor 5 W10243180 Valve Seat Cutter Code No.:...
Page 53 ZD321, ZD326, ZD331, WSM G GENERAL Nozzle Tester Code No.: 07909-31361 Application: Use to check the fuel injection pressure and spray pattern of nozzle. Measuring: 0 to 50 MPa range (0 to 500 kgf/cm , 0 to 7000 psi) W10246530 Plastigage Code No.: 07909-30241...
Page 54 ZD321, ZD326, ZD331, WSM G GENERAL NOTE • The following special tools are not provided, so make them referring to the figure. Valve Guide Replacing Tool Application: Use to press out and press fit the valve guide. D782-E2-ZD 20 mm dia. (0.79 in. dia.) 9.96 to 9.98 mm dia.
Page 55 ZD321, ZD326, ZD331, WSM G GENERAL Injection Pump Pressure Tester Application: Use to check fuel tightness of injection pumps. Pressure gauge full scale : More than 29.4 MPa (300 kgf/cm , 4267 psi) Copper gasket Flange (Material : Steel) Hex. nut 27 mm (1.06 in.) across the plat Injection Pipe PF 1/2 5 mm (0.20 in.)
Page 56 ZD321, ZD326, ZD331, WSM G GENERAL Flywheel Stopper Application: Use to loosen and tighten the flywheel screw. 200 mm (7.87 in.) 20 mm (0.79 in.) 30 mm (1.18 in.) 8 mm (0.31 in.) 10 mm dia. (0.39 in. dia.) W12365478 Crankshaft Bearing 1 Replacing Tool Application: Use to press out and press fit the crankshaft bearing 1.
Page 57: Special Tools For Machine
ZD321, ZD326, ZD331, WSM G GENERAL [2] SPECIAL TOOLS FOR MACHINE Relief Valve Pressure Tester Code No.: 07916-50045 Application: This allows easy measurement of relief set pressure. (1) Gauge (07916-50322) (6) Adaptor C (PS3/8) (07916-50371) (2) Cable (07916-50331) (7) Adaptor D (PT1/8) (07916-50381) (3) Threaded Joint (07916-50401) (8) Adaptor E (PS3/8) (07916-50392) (4) Threaded Joint (07916-50341)
Page 58: Implement Limitations
KUBOTA. Use with implements which are not sold or approved by KUBOTA and which exceed the maximum specifications listed below, or which are otherwise unfit for use with the KUBOTA Tractor may result in malfunctions or failures of the tractor, damage to other property and injury to the operator or others. [Any malfunctions or failures of the tractor resulting from use with improper implements are not covered by the warranty.]...
Page 59 ENGINE KiSC issued 04, 2007 A...
Page 60 SERVICING CONTENTS 1. TROUBLESHOOTING ..................1-S1 2. SERVICING SPECIFICATIONS ..............1-S5 [1] D782-E2-ZD ....................1-S5 [2] D1005-E2-ZD, D1305-E3-ZD..............1-S11 3. TIGHTENING TORQUES ................1-S18 4. CHECKING, DISASSEMBLING AND SERVICING........1-S20 [1] CHECKING AND ADJUSTING .............1-S20 (1) Engine Body..................1-S20 (2) Lubricating System ................1-S22 (3) Cooling System.................1-S22 (4) Fuel System ..................1-S25 [2] SEPARATING ENGINE .................1-S29 [3] DISASSEMBLING AND ASSEMBLING..........1-S32 (1) Cylinder Head and Valve ..............1-S32...
Page 61: Troubleshooting
ZD321, ZD326, ZD331, WSM ENGINE 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page Engine Does Not No fuel Replenish fuel Start Air in the fuel system Vent air G-36 Water in the fuel system Change fuel and – repair or replace fuel system Fuel pipe clogged Clean or replace...
Page 62 ZD321, ZD326, ZD331, WSM ENGINE Reference Symptom Probable Cause Solution Page Engine Revolution Is Fuel filter clogged or dirty Replace G-30 Not Smooth Air cleaner clogged Clean or replace G-24 Fuel leak due to loose injection pipe retaining nut Tighten retaining nut 1-S32 Injection pump malfunctioning Replace...
Page 63 ZD321, ZD326, ZD331, WSM ENGINE Reference Symptom Probable Cause Solution Page Deficient Output Incorrect injection timing Adjust 1-S25, 37, Engine’s moving parts seem to be seizing Repair or replace – Injection pump malfunctioning Replace 1-S37, 42 Deficient nozzle injection Replace nozzle 1-S33 Compression leak Check the...
Page 64 ZD321, ZD326, ZD331, WSM ENGINE Reference Symptom Probable Cause Solution Page High Oil Pressure Different type of oil Use specified type of Relief valve defective Replace – Engine Overheated Engine oil insufficient Replenish Fan belt broken or elongated Replace or adjust G-27 Coolant insufficient Replenish...
Page 65: Servicing Specifications
ZD321, ZD326, ZD331, WSM ENGINE 2. SERVICING SPECIFICATIONS [1] D782-E2-ZD ENGINE BODY Item Factory Specification Allowable Limit Valve Clearance (Cold) 0.145 to 0.185 mm – 0.00571 to 0.00728 in. Compression Pressure 2.84 to 3.24 MPa 2.26 MPa 29.0 to 33.0 kgf/cm 23.0 kgf/cm 413 to 469 psi 327 psi...
Page 66 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Rocker Arm Shaft to Rocker Arm Oil Clearance 0.016 to 0.045 mm 0.15 mm 0.00063 to 0.00177 in. 0.0059 in. Rocker Arm Shaft O.D. 10.473 to 10.484 mm –...
Page 67 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Idle Gear Shaft to Idle Gear Bushing Oil Clearance 0.020 to 0.084 mm 0.10 mm 0.00079 to 0.00331 in. 0.0039 in. Idle Gear Shaft O.D. 19.967 to 19.980 mm –...
Page 68 ZD321, ZD326, ZD331, WSM 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 – 1.33697 to 1.33760 in. Crankpin Bearing I.D.
Page 69 ZD321, ZD326, ZD331, WSM 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 28 to 64 psi 21 psi...
Page 70 ZD321, ZD326, ZD331, WSM ENGINE FUEL SYSTEM Item Factory Specification Allowable Limit Injection Pump Injection Timing 0.28 to 0.31 rad – (3200 min (rpm)) (16 to 18°) before T.D.C. Pump Element Fuel Tightness – 13.73 MPa 140 kgf/cm 1991 psi Delivery Valve Fuel Tightness 10 seconds...
Page 71: D1005-E2-Zd, D1305-E3-Zd
ZD321, ZD326, ZD331, WSM ENGINE [2] D1005-E2-ZD, D1305-E3-ZD ENGINE BODY Item Factory Specification Allowable Limit Valve Clearance (Cold) 0.145 to 0.185 mm – 0.00571 to 0.00728 in. Compression Pressure 3.73 to 4.11 MPa 2.26 MPa 38.0 to 42.0 kgf/cm 23.0 kgf/cm 541 to 597 psi 327 psi Difference among Cylinders...
Page 72 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Rocker Arm Shaft to Rocker Arm Clearance 0.016 to 0.045 mm 0.10 mm 0.00063 to 0.0017 in. 0.0039 in. Rocker Arm Shaft O.D. 11.973 to 11.984 mm –...
Page 73 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Idle Gear Shaft to Gear Bushing Idle Gear 1 Clearance 0.020 to 0.054 mm 0.10 mm 0.00079 to 0.0021 in. 0.0039 in. Idle Gear Bushing I.D. 26.000 to 26.021 mm –...
Page 74 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Piston Ring Gap Top Ring 0.30 to 0.45 mm 1.25 mm 0.012 to 0.017 in. 0.0492 in. Second Ring 0.30 to 0.45 mm 1.25 mm 0.012 to 0.017 in. 0.0492 in.
Page 75 ZD321, ZD326, ZD331, WSM ENGINE ENGINE BODY (Continued) Item Factory Specification Allowable Limit Crankshaft to Crankshaft Bearing 2 Oil Clearance 0.034 to 0.095 mm 0.20 mm [D1005-E2-ZD] 0.0014 to 0.0037 in. 0.0079 in. Crankshaft Journal O.D. 47.934 to 47.950 mm –...
Page 76 ZD321, ZD326, ZD331, WSM ENGINE LUBRICATING SYSTEM Item Factory Specification Allowable Limit Engine Oil Pressure At Idle Speed More than 49 kPa – 0.50 kgf/cm 7.1 psi At Rated Speed 197 to 441 kPa 147 kPa 2.00 to 4.50 kgf/cm 1.50 kgf/cm 28.5 to 64.0 psi 21.3 psi...
Page 77 ZD321, ZD326, ZD331, WSM ENGINE FUEL SYSTEM Item Factory Specification Allowable Limit Injection Pump Injection Timing 0.30 to 0.33 rad – (17 to 19°) before T.D.C. Pump Element Fuel Tightness – 13.73 MPa 140.0 kgf/cm 1991 psi Delivery Valve Fuel Tightness 10 seconds 5 seconds 13.73 →...
Page 78: Tightening Torques
ZD321, ZD326, ZD331, WSM ENGINE 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts : See page G-9.) [D782-E2-ZD] Item Size x Pitch N·m kgf·m lbf·ft *Cylinder head cover screw M6 x 1...
Page 79 ZD321, ZD326, ZD331, WSM ENGINE [D1005-E2-ZD, D1305-E3-ZD] Item Size x Pitch N·m kgf·m lbf·ft Cylinder head cover screw M7 x 1.0 7 to 8 0.7 to 0.9 5 to 6 (D1005-E2-ZD) Cylinder head cover screw M6 x 1.0 9.81 to 11.2 1.00 to 1.15 7.23 to 8.31 *Cylinder head screw...
Page 80: Checking, Disassembling And Servicing
ZD321, ZD326, ZD331, WSM 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 glow plugs (or nozzles).
Page 81 ZD321, ZD326, ZD331, WSM ENGINE Valve Clearance IMPORTANT • Valve clearance must be checked and adjusted when engine is cold. 1. Remove the cylinder head cover and the glow plugs. 2. Align the “1TC” mark (1) on the flywheel and alignment mark so that the No.
Page 82: Lubricating System
ZD321, ZD326, ZD331, WSM 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. 3.
Page 83 ZD321, ZD326, ZD331, WSM 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. 4.
Page 84 ZD321, ZD326, ZD331, WSM ENGINE Thermostat Valve Opening Temperature 1. Suspend the thermostat in the water by a string with its end inserted between the valve and seat. 2. Heating the water gradually, read the temperature when the valve opens and leaves the string. 3.
Page 85: Fuel System
ZD321, ZD326, ZD331, WSM ENGINE (4) Fuel System Injection Timing 1. Remove the injection pipes. 2. Remove the engine stop solenoid. 3. Turn the flywheel counterclockwise (viewed from flywheel side) until the fuel fills up to the hole of the delivery valve holder (2) for No.
Page 86 5. Set the speed control lever to the maximum speed position. 6. Run the starter to increase the pressure. 7. If the pressure can not reach the allowable limit, replace the pump with new one or repair with a Kubota-authorized pump service shop. 13.73 MPa...
Page 87 ZD321, ZD326, ZD331, WSM ENGINE CAUTION • Check the nozzle injection pressure and condition after confirming that there is nobody standing in the direction the fume goes. If the fume from the nozzle directly contacts the human body, cells may be destroyed and blood poisoning may be caused.
Page 88 ZD321, ZD326, ZD331, WSM ENGINE Nozzle Holder 1. Secure the nozzle retaining nut (7) with a vise. 2. Remove the nozzle holder (1), and take out parts inside. (When reassembling) • Assemble the nozzle in clean fuel oil. • Install the push rod (4), noting its direction. •...
Page 89: Separating Engine
ZD321, ZD326, ZD331, WSM ENGINE [2] SEPARATING ENGINE Draining Engine Oil 1. Park the machine on level ground. 2. Start and warm up the engine for approx. 5 minutes. 3. Place an oil pan underneath the engine. 4. Remove the drain plug (1) to drain oil. 5.
Page 90 ZD321, ZD326, ZD331, WSM ENGINE Draining Coolant CAUTION • Never open the radiator cap while operating or immediately after stopping. Otherwise, hot water will spout out from the radiator. Wait for more than ten minutes to cool the radiator, before opening the cap. 1.
Page 91 ZD321, ZD326, ZD331, WSM ENGINE Fan Shroud, Electric Wiring and Others 1. Disconnect the wiring connectors for engine stop solenoid, glow plug, coolant temperature sensor, engine oil pressure switch and dynamo. 2. Remove the positive cable (9) from starter motor. 3.
Page 92: Disassembling And Assembling
ZD321, ZD326, ZD331, WSM ENGINE Dynamo, Fan Belt and Muffler 1. Remove the radiator hoses (1), (4). 2. Remove the cooling fan (2) and fan pulley. 3. Remove the dynamo (9) and fan belt. 4. Remove the muffler (5). 5. Remove the starter (6). 6.
Page 93 ZD321, ZD326, ZD331, WSM ENGINE Nozzle Holder Assembly and Glow Plug 1. Remove the overflow pipe (1). 2. Remove the nozzle holder assemblies (4). 3. Remove the copper gasket (5) and heat seal (6). 4. Remove the lead (2) from the glow plugs (3). 5.
Page 94 ZD321, ZD326, ZD331, WSM ENGINE Rocker Arm and Push Rod 1. Remove the rocker arm bracket screws. 2. Detach the rocker arm assembly (1). 3. Remove the push rods (2). (When reassembling) • When putting the push rods (2) onto the tappets (3), check to see if their ends are properly engaged with the dimples.
Page 95 ZD321, ZD326, ZD331, WSM ENGINE Cylinder Head and Cylinder Head Gasket 1. Loosen the pipe clamps (1), and remove the water return pipe (2). 2. Remove the cylinder head screw in the order of (n) to (a) and remove the cylinder head. 3.
Page 96: Gear Case And Timing Gears
ZD321, ZD326, ZD331, WSM 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 97 ZD321, ZD326, ZD331, WSM ENGINE Injection Pump and Speed Control Plate (D782-E2-ZD) 1. Remove the socket head screws and nuts, and remove the injection pump (1). 2. Remove the screws and separate the speed control plate (2), taking care not to damage the governor spring (3). 3.
Page 98 ZD321, ZD326, ZD331, WSM ENGINE Gear Case (D782-E2-ZD) 1. Remove the screw (1). 2. Disconnect the start spring (2) in the speed control plate mounting hole. 3. Remove the gear case (3). (When reassembling) • Apply a liquid gasket (Three Bond 1215 or equivalent) to both sides of the gear case gasket (4).
Page 99 ZD321, ZD326, ZD331, WSM ENGINE Idle Gear (D782-E2-ZD) 1. Remove the external snap ring (3), the collar (2) and the idle gear (1). 2. Remove the idle gear shaft mounting screws (4). 3. Remove the idle gear shaft (5) (if necessary). (When reassembling) •...
Page 100 ZD321, ZD326, ZD331, WSM ENGINE Fuel Camshaft (D782-E2-ZD) 1. Remove the retaining plate (6). 2. Remove the fork lever holder mounting screws (8), then draw out the injection pump gear (1) and fuel camshaft (7) with the governor fork assembly. (When reassembling) •...
Page 101 ZD321, ZD326, ZD331, WSM ENGINE Gear Case (D1005-E2-ZD) 1. Remove the gear case. (When reassembling) • Grease thinly to the oil seal, and install it, ensuring the lip does not come off. (1) Gear Case A : Bolt Length = 45 mm (1.8 in.) B : Bolt Length = 50 mm (2.0 in.) C : Bolt Length = 55 mm (2.2 in.) D : Bolt Length = 65 mm (2.6 in.)
Page 102 ZD321, ZD326, ZD331, WSM ENGINE Speed Control Plate (D1005-E2-ZD, D1305-E3-ZD) 1. Remove the engine stop solenoid. 2. Remove the speed control plate (1). (When reassembling) • Apply a liquid gasket (Three Bond 1215 or equivalent) to both sides of the solenoid cover gasket and control plate gasket. •...
Page 103 ZD321, ZD326, ZD331, WSM ENGINE Cam Gear, Idle Gear 1 and Governor Gear (D1005-E2-ZD, D1305-E3-ZD) 1. Remove the idle gear 1 (4). 2. Remove the fuel camshaft stopper (7). 3. Draw out the injection pump gear (1) with fuel camshaft (8). 4.
Page 104: Piston And Connecting Rod
ZD321, ZD326, ZD331, WSM ENGINE (3) Piston and Connecting Rod Oil Pan and Oil Strainer (D782-E2-ZD, D1005-E2-ZD) 1. Remove the oil pan mounting screws (5). 2. Remove the oil pan (4). 3. Remove the oil strainer (3). (When reassembling) • After cleaning the oil strainer, check to see that the filter mesh in clean, and install it.
Page 105 ZD321, ZD326, ZD331, WSM ENGINE Pistons 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. 3.
Page 106 ZD321, ZD326, ZD331, WSM ENGINE Piston Ring and Connecting Rod 1. Remove the piston rings using a piston ring tool. 2. Remove the piston pin (7), and separate the connecting rod (6) from the piston (5). (When reassembling) • When installing the ring, assemble the rings so that the manufacturer’s mark (12) near the gap faces the top of the piston.
Page 107: Flywheel And Crankshaft
ZD321, ZD326, ZD331, WSM ENGINE (4) Flywheel and Crankshaft Flywheel 1. Secure the flywheel to keep it from turning, using a flywheel stopper. 2. Remove all flywheel screws (1) and then remove the flywheel (2). (When reassembling) • Align the “1TC” mark (a) on the outer surface of the flywheel horizontally with the alignment mark.
Page 108 ZD321, ZD326, ZD331, WSM ENGINE Bearing Case Cover 1. Remove the bearing case cover mounting screws. 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 109 ZD321, ZD326, ZD331, WSM ENGINE Crankshaft Assembly (D782-E2-ZD) 1. Remove the main bearing case screw 2 (1). 2. Turn the crankshaft to set the crank pin of the third cylinder to the bottom dead center. Then draw out the crankshaft until the crank pin of the second cylinder comes to the center of the third cylinder.
Page 110 ZD321, ZD326, ZD331, WSM ENGINE Crankshaft Assembly (D1305-E3-ZD) 1. Remove the main bearing case screw 2. 2. Turn the crankshaft to set the crankpin of the third cylinder to the A. Then draw out the crankshaft until the crankpin of the second cylinder comes to the center of the third cylinder.
Page 111 ZD321, ZD326, ZD331, WSM 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). 2. Remove the main bearing case assembly 2 (2) and the main bearing case assembly (3) as above.
Page 112: Servicing
ZD321, ZD326, ZD331, WSM ENGINE [4] SERVICING (1) Cylinder Head and Valves 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.
Page 113 ZD321, ZD326, ZD331, WSM ENGINE 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. 3. Measure the clearance with a thickness gauge. 4.
Page 114 ZD321, ZD326, ZD331, WSM ENGINE Valve Recessing 1. Clean the cylinder head surface, valve face and valve 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 115 ZD321, ZD326, ZD331, WSM ENGINE Replacing Valve Guide (When removing) 1. Press out the used valve guide using a valve guide replacing tool. (See page “SPECIAL TOOLS”.) (When installing) 1. Clean a new valve guide and valve guide bore, and apply engine oil to them.
Page 116 ZD321, ZD326, ZD331, WSM 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 117 ZD321, ZD326, ZD331, WSM 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 valve spring on a surface plate, place a square on the side of the valve spring.
Page 118 ZD321, ZD326, ZD331, WSM ENGINE Oil Clearance between Rocker Arm and Rocker Arm Shaft 1. Measure the rocker arm shaft O.D. with an outside micrometer. 2. Measure the rocker arm I.D. with an inside micrometer, and then calculate the oil clearance. 3.
Page 119 ZD321, ZD326, ZD331, WSM ENGINE Oil Clearance between Tappet and Tappet Guide Bore 1. Measure the tappet O.D. with an outside micrometer. 2. Measure the I.D. of the tappet guide bore with a cylinder gauge, and calculate the oil clearance. 3.
Page 120: Timing Gears, Camshaft And Governor Gear
ZD321, ZD326, ZD331, WSM ENGINE (2) Timing Gears, Camshaft and Governor Gear Timing Gear Backlash 1. Set a dial indicator (lever type) with its tip on the gear tooth. 2. Move the gear to measure the backlash, holding its mating gear. 3.
Page 121 ZD321, ZD326, ZD331, WSM ENGINE Idle Gear and Idle Gear 1 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.
Page 122 ZD321, ZD326, ZD331, WSM ENGINE Cam Height 1. Measure the height of the cam at its highest point with an outside micrometer. 2. If the measurement is less than the allowable limit, replace the camshaft. [D782-E2-ZD] 26.88 mm Factory spec. 1.058 in.
Page 123: Piston And Connecting Rod
ZD321, ZD326, ZD331, WSM ENGINE Oil Clearance between Idle Gear, Idle Gear 1, Idle Gear Shaft and Idle Gear Bushing 1. Measure the idle gear shaft O.D. with an outside micrometer. 2. Measure the idle gear bushing I.D. with an inside micrometer, and calculate the oil clearance.
Page 124 ZD321, ZD326, ZD331, WSM ENGINE Oil Clearance between Piston Pin and Small End Bushing 1. Measure the piston pin O.D. where it contacts the bushing with an outside micrometer. 2. Measure the small end bushing I.D. with an inside micrometer, and calculate the oil clearance.
Page 125 ZD321, ZD326, ZD331, WSM ENGINE Replacing Small End Bushing (When removing) 1. Press out the used bushing using a small end bushing replacing tool. (See page “SPECIAL TOOLS”.) (When installing) 1. Clean a new small end bushing and bore, and apply engine oil to them.
Page 126 ZD321, ZD326, ZD331, WSM ENGINE Piston Ring Gap 1. Insert the piston ring into the lower part of the cylinder (the least worn out part) with a piston. 2. Measure the ring gap with a thickness gauge. 3. If the measurement exceeds the allowable limit, replace the piston ring.
Page 127 ZD321, ZD326, ZD331, WSM ENGINE Clearance between Piston ring and Piston Ring Groove 1. Clean the rings and the ring grooves, and install each ring in its groove. 2. Measure the clearance between the ring and the groove with a feeler gauge or depth gauge.
Page 128: Crankshaft
ZD321, ZD326, ZD331, WSM 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. 3. If the measurement exceeds the allowable limit, replace the thrust bearings.
Page 129 ZD321, ZD326, ZD331, WSM 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 130 ZD321, ZD326, ZD331, WSM ENGINE (Reference) • Undersize dimensions of crankpin [D782-E2-ZD] 0.20 mm 0.40 mm Undersize 0.0079 in. 0.016 in. 2.3 to 2.7 mm radius 2.3 to 2.7 mm radius Dimension A 0.091 to 0.10 in.radius 0.091 to 0.10 in.radius 1.0 to 1.5 mm relief 1.0 to 1.5 mm relief *Dimension B...
Page 131 ZD321, ZD326, ZD331, WSM 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. 3.
Page 132 ZD321, ZD326, ZD331, WSM ENGINE (Reference) • Undersize dimensions of crankshaft journal [D782-E2-ZD] 0.2 mm 0.4 mm Undersize 0.008 in. 0.016 in. 1.8 to 2.2 mm radius 1.8 to 2.2 mm radius Dimension A 0.071 to 0.087 in.radius 0.071 to 0.087 in.radius 1.0 to 1.5 mm relief 1.0 to 1.5 mm relief *Dimension B...
Page 133 ZD321, ZD326, ZD331, WSM 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 baring case screws 1 to the specified torque, and remove the bearing case again.
Page 134 ZD321, ZD326, ZD331, WSM ENGINE [D1305-E3-ZD] 0.034 to 0.103 mm Factory spec. Oil clearance between 0.0014 to 0.00405 in. crankshaft journal and 0.20 mm crankshaft bearing 2 Allowable limit 0.0079 in. Crankshaft journal O.D. 51.921 to 51.940 mm Factory spec. (Intermediate) 2.0442 to 2.0448 in.
Page 135 ZD321, ZD326, ZD331, WSM ENGINE [D1305-E3-ZD] 0.20 mm 0.40 mm Undersize 0.0079 in. 0.016 in. 2.3 to 2.7 mm radius 2.3 to 2.7 mm radius Dimension A 0.091 to 0.10 in. radius 0.091 to 0.10 in. radius 1.0 to 1.5 mm relief 1.0 to 1.5 mm relief *Dimension B 0.040 to 0.059 in.
Page 136: Cylinder
ZD321, ZD326, ZD331, WSM ENGINE (5) Cylinder Cylinder Wear 1. Measure the I.D. of the cylinder at the six positions (see figure) with a cylinder gauge to find the maximum and minimum I.D.’s. 2. Get the difference (Maximum wear) between the maximum and the minimum I.D.’s.
Page 137: Oil Pump (D782-E2-Zd)
ZD321, ZD326, ZD331, WSM ENGINE Correcting Cylinder 1. When the cylinder is worn beyond the allowable limit, bore and hone it to the specified dimension. [D782-E2-ZD] 67.250 to 67.269 mm Factory spec. 2.6477 to 2.6483 in. Cylinder liner I.D. 67.400 mm Allowable limit 2.6535 in.
Page 138: Oil Pump (D1005-E2-Zd, D1305-E3-Zd)
ZD321, ZD326, ZD331, WSM ENGINE Clearance between Outer Rotor and Pump Body 1. Measure the clearance between the outer rotor and the pump body with a thickness gauge. 2. If the clearance exceeds the factory specifications, replace the oil pump rotor assembly. Clearance between 0.070 to 0.15 mm outer rotor and pump...
Page 139 TRANSAXLE KiSC issued 04, 2007 A...
Page 140 MECHANISM CONTENTS 1. STRUCTURE ....................2-M1 2. TRAVELLING SYSTEM ................2-M2 [1] HYDROSTATIC TRANSMISSION ............2-M2 (1) Structure .................... 2-M2 (2) Check Valve and High Pressure Relief Valve ........2-M3 (3) Oil Flow ....................2-M4 (4) Power Trains Operation ..............2-M4 (5) Control Linkage..................
Page 141: Structure
ZD321, ZD326, ZD331, WSM TRANSAXLE 1. STRUCTURE (1) Bevel Gear Section (3) Hydrostatic Transmission (4) Brake Section (5) Final Reduction Gear Section (2) PTO Section Transmission consists of bevel gear section (1) hydrostatic transmission (3), brake section (4), final reduction gear section (5), and PTO section (2).
Page 142: Travelling System
ZD321, ZD326, ZD331, WSM TRANSAXLE 2. TRAVELLING SYSTEM [1] HYDROSTATIC TRANSMISSION (1) Structure (1) Lubricating Orifice (6) Slot Guide (11) Swashplate (16) Cylinder Block (Motor) (2) Pump Shaft (7) Cradle Bearing (12) Piston (Motor) (17) Check Valve Spring (3) Brake Shaft (8T) (8) Cylinder Block (Pump) (13) Needle Bearing (18) Relief Valve Spring...
Page 143: Check Valve And High Pressure Relief Valve
ZD321, ZD326, ZD331, WSM TRANSAXLE (2) Check Valve and High Pressure Relief Valve The check and high-pressure relief valve consists of pressure poppet (2), check valve seat (1), relief valve spring (3), spring guide (4) and check valve spring (5). The valve is used to prevent an overload that would happen at a quick start, sudden stop or even during usual running.
Page 144: Oil Flow
ZD321, ZD326, ZD331, WSM TRANSAXLE (3) Oil Flow (1) Transmission Case (5) Regulator Valve (9) Cylinder Block (Pump) (13) Cylinder Block (Motor) (2) Hydraulic Pump (6) PTO Clutch (10) Lubricating Orifice (14) Check and High Pressure (3) Oil Filter Cartridge (7) Oil Cooler (11) Swashplate Relief Valve...
Page 145: Power Trains Operation
ZD321, ZD326, ZD331, WSM TRANSAXLE (4) Power Trains Operation (1) Check and High Pressure (4) Oil Cooler (7) Neutral Orifice (10) Pump Relief Valve (5) Motor (8) Check Valve (11) Suction Oil Filter (2) Oil Filter (6) Lubricating Orifice (9) High Pressure Relief Valve (12) Hydraulic Pump (3) Regulator Valve (Charge Relief Valve)
Page 146: Control Linkage
ZD321, ZD326, ZD331, WSM TRANSAXLE (5) Control Linkage (1) Motion Control Lever (3) Speed Limit Spring (4) Speed Control Rod (5) Trunnion Arm (2) Speed Shaft The motion control lever (1) and the trunnion shaft of variable swashplate are linked with the speed shaft (2), speed control rod (4) and the trunnion arm (5).
Page 147: Final Reduction Gear Section
ZD321, ZD326, ZD331, WSM TRANSAXLE (6) Final Reduction Gear Section As for this machine, power is transmitted from the 8T gear on the brake shaft (1) to the rear axle (4) through 53T gear (3), 17T or 19T gear shaft (2) and 49T or 51T gear (5).
Page 148: Pto System
ZD321, ZD326, ZD331, WSM TRANSAXLE (7) PTO System PTO Clutch and Valve (1) PTO Valve Lever (8) 35T Gear (17) Center Case, Front Cover C : From Hydraulic Pump (2) Regulator Valve (9) Hydraulic Pump (18) PTO Shaft D : From Hydraulic Pump to (3) PTO Brake Plate (10) Center Case, Rear Cover (19) Oil Filter Cartridge...
Page 149 ZD321, ZD326, ZD331, WSM TRANSAXLE PTO Clutch “Engaged” (1) PTO Clutch Valve (2) Poppet (3) Center Case, Front Cover (4) Brake Pressure Plate (5) Center Case (6) Center Case, Rear Cover (7) Clutch Gear (8) Spring (9) Clutch Piston (10) Brake Disc (11) Clutch Spline Boss (12) Clutch Shaft (PTO Shaft) (A) From Hydraulic Pump...
Page 150 ZD321, ZD326, ZD331, WSM TRANSAXLE PTO Clutch “Disengaged” (1) PTO Clutch Valve (2) Poppet (3) Center Case, Front Cover (4) Brake Pressure Plate (5) Center Case (6) Center Case, Rear Cover (7) Clutch Gear (8) Spring (9) Clutch Piston (10) Brake Disc (11) Clutch Spline Boss (12) Clutch Shaft (PTO Shaft) (A) From Hydraulic Pump...
Page 151: Parking Brake
ZD321, ZD326, ZD331, WSM TRANSAXLE (8) Parking Brake (1) Brake Pedal (5) Brake Rod (8) Brake Spring (11) Brake Disk (2) Parking Lock Pedal (6) Brake Assembly (9) Ball (12) Brake Plate (3) Brake Pedal Return Spring (7) Brake Arm (10) Actuator (13) HST Motor Shaft (Brake) (4) Brake Shaft...
Page 152 SERVICING CONTENTS 1. TROUBLESHOOTING ..................2-S1 2. SERVICING SPECIFICATIONS ..............2-S3 3. TIGHTENING TORQUES ................2-S4 4. CHECKING AND ADJUSTING ..............2-S5 5. DISASSEMBLING AND ASSEMBLING ............2-S14 [1] SEPARATING TRANSAXLE ASSEMBLY ..........2-S14 [2] DISASSEMBLING TRANSAXLE CENTER CASE.......2-S19 [3] DISASSEMBLING PTO CLUTCH SHAFT ASSEMBLY......2-S21 [4] DISASSEMBLING HYDROSTATIC TRANSMISSION AND REAR AXLE GEAR CASE ASSEMBLY............2-S26 [5] DISASSEMBLING REAR AXLE GEAR CASE........2-S31 6.
Page 153: Troubleshooting
ZD321, ZD326, ZD331, WSM TRANSAXLE 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page Vehicle Will Not Stop Improper neutral adjustment Adjust neutral 2-S6 in Neutral Position Improper speed control rod adjustment Adjust 2-S6 Vehicle Jerky and Transmission oil insufficient Replenish 2-S14 Noisy When Starting Air entering from suction pipe...
Page 154 ZD321, ZD326, ZD331, WSM TRANSAXLE TRAVELLING GEAR SHIFT SECTION Reference Symptom Probable Cause Solution Page Noise from Transmission oil insufficient Refill 2-S14 Transmission Gear worn or broken Replace – Bearings worn Replace – W1013580 PTO SECTION PTO Clutch Slip Operating pressure is low Check –...
Page 155: Servicing Specifications
ZD321, ZD326, ZD331, WSM TRANSAXLE 2. SERVICING SPECIFICATIONS Item Factory Specification Allowable Limit Regulator Valve Setting pressure 0.75 to 0.95 MPa – (HST Charge Relief Valve) [at engine speed 7.7 to 9.6 kgf/cm ZD321, ZD326 : 110 to 130 psi 3200 min (rpm) ZD331 :...
Page 156: Tightening Torques
ZD321, ZD326, ZD331, WSM TRANSAXLE 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts : See page G-9.) Item N·m kgf·m lbf·ft Motion control lever mounting bolt and nut 18 to 20 1.8 to 2.1 13 to 15...
Page 157: Checking And Adjusting
ZD321, ZD326, ZD331, WSM TRANSAXLE 4. CHECKING AND ADJUSTING Checking Neutral 1. Park machine safely. 2. Set the motion control levers are in the NEUTRAL position. 3. Move the PTO lever to OFF position and apply the parking brake. 4. With the operator on the seat and start the engine. 5.
Page 158 ZD321, ZD326, ZD331, WSM TRANSAXLE Adjusting Neutral CAUTION To avoid personal injury: • Park the machine on a hard and level surface. • If it is necessary to run engine in an enclosed area, use a gas tight exhaust pipe extension to remove the fumes. •...
Page 159 ZD321, ZD326, ZD331, WSM TRANSAXLE Checking Motion Control Lever Neutral Position CAUTION To avoid personal injury: • Park the machine on a hard and level surface. • If it is necessary to run engine in an enclosed area, use a gas tight exhaust pipe extension to remove the fumes.
Page 160 ZD321, ZD326, ZD331, WSM TRANSAXLE Adjusting Maximum Speed CAUTION To avoid personal injury: • Park the machine on a hard and level surface. • If it is necessary to run engine in an enclosed area, use a gas tight exhaust pipe extension to remove the fumes. •...
Page 161 ZD321, ZD326, ZD331, WSM TRANSAXLE Checking Motion Control Lever Alignment CAUTION • When checking, park the tractor on flat ground, apply the parking brake. 1. Check the gap (A) and space (B) between the motion control levers, at the maximum forward position. If positions of the motion control levers are unequal, an adjustment is necessary.
Page 162 ZD321, ZD326, ZD331, WSM TRANSAXLE Checking Hydrostatic Transmission CAUTION • When checking, park the machine on flat ground, apply the parking brake. • Sit on operator’s seat for checking. 1. After worming up the machine, apply the parking brake and set the stop wood (chock) to the rear wheels.
Page 163 ZD321, ZD326, ZD331, WSM TRANSAXLE PTO Clutch Operating Pressure (Hydrostatic Transmission Charge Pressure) CAUTION • When checking, park the tractor on flat ground, apply the parking brake. 1. Remove the plug (1), then install the adaptor (2) cable and pressure gauge. 2.
Page 164 ZD321, ZD326, ZD331, WSM TRANSAXLE Checking and Adjusting Parking Brake CAUTION • Park the machine on a firm and level surface. • Stop the engine and chock the wheels before checking or adjusting. IMPORTANT • Wrong adjustment may cause machine damage. Check brake spring 1.
Page 165 ZD321, ZD326, ZD331, WSM TRANSAXLE Checking Parking Brake on the Slope 1. Place the machine on a 17 ° ramp A. 2. Apply the parking brake. 3. Place the motion control levers in “NEUTRAL LOCK” position and shut off the engine. 4.
Page 166: Disassembling And Assembling
ZD321, ZD326, ZD331, WSM TRANSAXLE 5. DISASSEMBLING AND ASSEMBLING [1] SEPARATING TRANSAXLE ASSEMBLY Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. • Allow transmission case to cool down sufficiently; oil can be hot and may cause burns.
Page 167 ZD321, ZD326, ZD331, WSM TRANSAXLE Battery CAUTION • When disconnecting the battery cables, disconnect the negative cable from the battery first. When connecting, connect the positive cable to the battery first. 1. Remove the battery cover (1). 2. Disconnect the negative cable (3) from the battery. 3.
Page 168 ZD321, ZD326, ZD331, WSM TRANSAXLE Upper Frame, Oil Cooler and Others 1. Disconnect the return hose (1) and fuel hose (2). 2. Remove the stopper (13) and remove the oil cooler (3). 3. Remove the throttle cable (5). 4. Remove the rod (4). 5.
Page 169 ZD321, ZD326, ZD331, WSM TRANSAXLE Bonnet, Fuel Hose, Wiring Harness and Others 1. Remove the bonnet (1). 2. Remove the engine stopper (3). 3. Disconnect the wiring harness (2) from engine body. 4. Disconnect the fuel hose (4). (1) Bonnet (3) Engine Stopper (2) Wiring Harness (4) Fuel Hose...
Page 170 ZD321, ZD326, ZD331, WSM TRANSAXLE ROPS, Rear Wheel and Others 1. Remove the oil cooler pipes (2). 2. Remove the ROPS upper, and remove the ROPS lower (LH) (1) and ROPS lower (RH) (3). 3. Remove the universal joint (4) from the transaxle. 4.
Page 171: Disassembling Transaxle Center Case
ZD321, ZD326, ZD331, WSM TRANSAXLE [2] DISASSEMBLING TRANSAXLE CENTER CASE Center Case Rear Cover 1. Remove the oil filter cartridge (1). 2. Remove the delivery pipe (3). 3. REmove the center case rear cover (4). NOTE • Remember to remove the hex. socket head screw hidden behind the filter cartridge (1) •...
Page 172 ZD321, ZD326, ZD331, WSM TRANSAXLE Regulator Valve (HST Charge Pressure Relief Valve) 1. Remove the plug (3). 2. Remove the spring (2) and poppet (1). (1) Poppet (3) Plug (2) Spring W1029406 PTO Clutch Lever 1. Remove the lever stopper and remove the PTO clutch lever (2). (When reassembling) •...
Page 173: Disassembling Pto Clutch Shaft Assembly
ZD321, ZD326, ZD331, WSM TRANSAXLE [3] DISASSEMBLING PTO CLUTCH SHAFT ASSEMBLY Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. • Allow transmission case to cool down sufficiently; oil can be hot and may cause burns.
Page 174 ZD321, ZD326, ZD331, WSM TRANSAXLE Draining Coolant CAUTION • Never open the radiator cap while operating or immediately after stopping. Otherwise, hot water will spout out from the radiator. Wait for more than ten minutes to cool the radiator, before opening the cap. 1.
Page 175 ZD321, ZD326, ZD331, WSM TRANSAXLE Bonnet, Fuel Hose, Wiring Harness and Others 1. Remove the snap pin and bonnet mounting screw, then remove the bonnet (3). 2. Disconnect the wiring connectors for engine stop solenoid, glow plug, coolant temperature sensor, engine oil pressure switch and dynamo.
Page 176 ZD321, ZD326, ZD331, WSM TRANSAXLE Oil Cooler, Radiator, Universal Joint and Others 1. Remove the bonnet cover (1) and ROPS connecting plate. 2. Remove the oil cooler (2). 3. Remove the radiator (3). 4. Remove the ROPS connecting plate under (4). 5.
Page 177 ZD321, ZD326, ZD331, WSM TRANSAXLE Center Case Rear Cover and PTO Clutch Shaft Assembly 1. Disconnect the delivery pipe (1). 2. Remove the center case rear cover (2). 3. Remove the pump shaft assembly (5). 4. Remove the PTO clutch shaft assembly (4). NOTE •...
Page 178: Disassembling Hydrostatic Transmission And Rear Axle Gear Case Assembly
ZD321, ZD326, ZD331, WSM TRANSAXLE [4] DISASSEMBLING HYDROSTATIC TRANSMISSION AND REAR AXLE GEAR CASE ASSEMBLY Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. •...
Page 179 ZD321, ZD326, ZD331, WSM TRANSAXLE Battery CAUTION • When disconnecting the battery cables, disconnect the negative cable from the battery first. When connecting, connect the positive cable to the battery first. 1. Remove the battery cover (1). 2. Disconnect the negative cable (3) from the battery. 3.
Page 180 ZD321, ZD326, ZD331, WSM TRANSAXLE Parking Brake Rod 1. Remove the parking brake rods (1). (When reassembling) NOTE • Replace the cotter pin (2) with new one. • After assembling the parking brake rods, be sure check the parking brake spring length and play. If the measurement is not within the factory specifications, adjust the spring length and play.
Page 181 ZD321, ZD326, ZD331, WSM TRANSAXLE Center Section (Port Block) 1. Separate the center section (1) and the hydrostatic transmission housing. NOTE • Take care not to damage the surface of cylinder blocks pistons and center section. 40 to 44 N·m Center section mounting Tightening torque 4.0 to 4.5 kgf·m...
Page 182 ZD321, ZD326, ZD331, WSM TRANSAXLE Swashplate 1. Remove the swashplate (1) from the housing. (1) Swashplate W1035905 Slot Guide and Cradle Bearing 1. Remove the slot guide (2) from the trunnion arm (1). 2. Remove the cradle bearing (3) from the housing. (1) Trunnion Arm (3) Cradle Bearing (2) Slot Guide...
Page 183: Disassembling Rear Axle Gear Case
ZD321, ZD326, ZD331, WSM TRANSAXLE [5] DISASSEMBLING REAR AXLE GEAR CASE Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. • Allow transmission case to cool down sufficiently; oil can be hot and may cause burns.
Page 184 ZD321, ZD326, ZD331, WSM TRANSAXLE Battery CAUTION • When disconnecting the battery cables, disconnect the negative cable from the battery first. When connecting, connect the positive cable to the battery first. 1. Remove the battery cover (1). 2. Disconnect the negative cable (3) from the battery. 3.
Page 185 ZD321, ZD326, ZD331, WSM TRANSAXLE Parking Brake Rod 1. Remove the parking brake rods (1). (When reassembling) NOTE • Replace the cotter pin (2) with new one. • After assembling the parking brake rods, be sure check the parking brake spring length and play. If the measurement is not within the factory specifications, adjust the spring length and play.
Page 186 ZD321, ZD326, ZD331, WSM TRANSAXLE Rear Axle 1. Remove the brake shaft (HST motor shaft) (5). 2. Remove the external snap ring (3) and remove the ball bearing (2) with puller. 3. Remove the final reduction gear (1) and gear shaft (4). 4.
Page 187: Servicing
ZD321, ZD326, ZD331, WSM TRANSAXLE 6. SERVICING [1] HYDROSTATIC TRANSMISSION Center Section 1. Check the surface (1) of center section for scratches or wear. If deep scratch or excessive wear is found, replace the hydrostatic transmission assembly. (1) Surface W1038177 Check and High Pressure Relief Valve 1.
Page 188 ZD321, ZD326, ZD331, WSM TRANSAXLE Pump Shaft 1. Check the bearing surface (3) and the ball bearing (2). 2. If the shaft is rough or grooved, replace it. 3. If the ball bearing is worn, replace it. (1) Pump Shaft (3) Bearing Surface (2) Ball Bearing W1038908...
Page 189: Transmission Case
ZD321, ZD326, ZD331, WSM TRANSAXLE [2] TRANSMISSION CASE Checking Bearing 1. Hold the inner race, and push and pull the outer race in all directions to check for wear and roughness. 2. Apply transmission fluid to the bearing, and hold the inner race. Then, turn the outer race to check rotation.
Page 190 ZD321, ZD326, ZD331, WSM TRANSAXLE Correcting of Tooth Contact 1. Proper contact - No adjustment. 2. Correcting of the heel contact and shallow contact - It is confirmed whether there is a shim (5). - The 16T or 18T bevel gear (6) can be moved to backward by doing to add the shim (5) when not is.
Page 191: Pto Clutch
ZD321, ZD326, ZD331, WSM TRANSAXLE [3] PTO CLUTCH Checking PTO Clutch Discs 1. Check the surface of the pressure plate (1), PTO clutch discs (2) and PTO clutch plates (3). 2. If excessive wear is found, replace it to a new one. (1) Pressure Plate (3) PTO Clutch Plate (2) PTO Clutch Disc...
Page 192 FRONT AXLE KiSC issued 04, 2007 A...
Page 193 MECHANISM CONTENTS 1. STRUCTURE ....................3-M1 KiSC issued 04, 2007 A...
Page 194 ZD321, ZD326, ZD331, WSM FRONT AXLE 1. STRUCTURE (1) Cap (3) Taper Roller Bearing (5) Center Pin (7) Slotted Nut (2) Taper Roller Bearing (4) Wheel Bracket (6) Front Axle (8) Lift Up Adjuster The front axle is constructed as shown above. The shape of the front axle is relatively simple, and the front axle is supported at its center with the center pin (5), so that steering operation is stable even on uneven grounds in a grass field.
Page 195 SERVICING CONTENTS 1. TROUBLESHOOTING ..................3-S1 2. SERVICING SPECIFICATIONS ..............3-S2 3. TIGHTENING TORQUES ................3-S3 4. CHECKING, DISASSEMBLING AND SERVICING........3-S4 [1] CHECKING AND ADJUSTING ...............3-S4 [2] DISASSEMBLING AND ASSEMBLING..........3-S5 (1) Separating Front Wheel and Wheel Bracket........3-S5 (2) Separating Front Axle Assembly............3-S6 KiSC issued 04, 2007 A...
Page 196: Troubleshooting
ZD321, ZD326, ZD331, WSM FRONT AXLE 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page Front Wheels Clearance between center pin and front axle Replace – Wander to Right or excessive Left Force of the lock nut which tighten the wheel Adjust 3-S5 bracket has become down...
Page 197: Servicing Specifications
ZD321, ZD326, ZD331, WSM FRONT AXLE 2. SERVICING SPECIFICATIONS Item Factory Specification Allowable Limit Front Axle End Play Clearance 0 to 0.2 mm 0.5 mm 0 to 0.008 in. 0.02 in. W1013874 KiSC issued 04, 2007 A 3-S2...
Page 198: Tightening Torques
ZD321, ZD326, ZD331, WSM FRONT AXLE 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts: See page G-9.) Item N·m kgf·m lbf·ft Wheel bolt and lock nut 20 to 25 2.1 to 2.5 15 to 18...
Page 199: Checking, Disassembling And Servicing
ZD321, ZD326, ZD331, WSM FRONT AXLE 4. CHECKING, DISASSEMBLING AND SERVICING [1] CHECKING AND ADJUSTING Adjusting Front Axle Pivot 1. Lift up and securely block the front of the machine. 2. Measure the clearance (A) between the front axle (4) and front axle support (3).
Page 200: Disassembling And Assembling
ZD321, ZD326, ZD331, WSM FRONT AXLE [2] DISASSEMBLING AND ASSEMBLING (1) Separating Front Wheel and Wheel Bracket Remove the Front Wheel 1. Inspect all parts for wear or damage. Replace the parts as needed. (When reassembling) • Apply grease to grease fittings. (See page G-8.) 20 to 25 N·m Front wheel mounting bolt Tightening torque...
Page 201: Separating Front Axle Assembly
ZD321, ZD326, ZD331, WSM FRONT AXLE (2) Separating Front Axle Assembly Battery CAUTION • When disconnecting the battery cables, disconnect the negative cable from the battery first. When connecting, connect the positive cable to the battery first. 1. Remove the battery cover (1). 2.
Page 202 ZD321, ZD326, ZD331, WSM FRONT AXLE Separating Front Axle Assembly 1. Remove the set spring and slotted nut (2). 2. Remove the cotter pin and clevis pin (6). 3. Remove the connecting plate (3). 4. Lift up and secure with jack stands or blocking the front of machine frame.
Page 203 HYDRAULIC SYSTEM KiSC issued 04, 2007 A...
Page 204 MECHANISM CONTENTS 1. HYDRAULIC CIRCUIT .................. 4-M1 2. HYDRAULIC PUMP ..................4-M2 3. HYDRAULIC CONTROL VALVE ..............4-M3 4. LIFT CYLINDER.................... 4-M6 5. MOWER LINKAGE ..................4-M7 KiSC issued 04, 2007 A...
Page 205: Hydraulic Circuit
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 1. HYDRAULIC CIRCUIT (1) PTO Clutch (4) Hydraulic Cylinder (7) Oil Filter (10) Hydraulic Pump (2) PTO Clutch Valve (5) Relief Valve (8) Regulator Valve (11) Oil Filter (3) Hydraulic Control Valve (6) Control Valve (9) Oil Cooler (12) Hydrostatic Transmission Assembly...
Page 206: Hydraulic Pump
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 2. HYDRAULIC PUMP The hydraulic pump is composed of the casing (1), cover (3), side plate (5), and two spur gears (drive gear (4) and driven gear (2)) that are in mesh. Hydraulic pump is driven by the pump drive shaft in the transmission case.
Page 207: Hydraulic Control Valve
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 3. HYDRAULIC CONTROL VALVE hydraulic system composed transmission case (oil tank), cushion oil filter, hydraulic pump, control valve, hydraulic cylinder and etc.. The new series product is provided with a built-in control valve in the case. The oil flows through the oil filter, and then the oil is sent to the control valve by the pump.
Page 208 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Neutral (1) To PTO Clutch and Hydrostatic Transmission (2) C (Cylinder) Port (3) Spool (4) P (Pump) Port (5) Valve Body (6) Relief Valve W1012655 The oil sent from the pump passes through a gap between the spool (3) and the valve body (5), through the regulator valve, and then flows to the PTO valve and HST charge circuit.
Page 209 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Down (1) To PTO Clutch and Hydrostatic Transmission (2) Spool (3) C (Cylinder) Port (4) P (Pump) Port (5) Valve Body (6) Relief Valve A : Drain directly to the Transmission Center Case W1013905 The oil sent from the pump passes through a gap between the spool (2) and the valve body (5), through the regulator valve, and then the oil flows to the PTO valve and HST charge circuit.
Page 210: Lift Cylinder
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 4. LIFT CYLINDER (1) Piston Rod (2) Scraper (3) Packing (4) Cylinder (5) Snap Ring W1014031 The lift cylinder consists of the cylinder (4), piston rod (1) and other parts as shown in the figure above. This cylinder is single acting type.
Page 211: Mower Linkage
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 5. MOWER LINKAGE (1) Cutting Height Adjusting Dial (2) Dial Cam Gear (3) Lift Cylinder (4) Lift Shaft (5) Adjusting Cam (6) Horizon Plate (7) Front Arm W1014267 The lifting of mower is performed by the hydraulic system on the machine. Front arm (7) and lift shaft are linked with horizon plate (6).
Page 212 SERVICING CONTENTS 1. TROUBLESHOOTING ..................4-S1 2. SERVICING SPECIFICATIONS ..............4-S2 3. TIGHTENING TORQUES ................4-S3 4. CHECKING, DISASSEMBLING AND SERVICING........4-S4 [1] HYDRAULIC CONTROL VALVE, PUMP AND CYLINDER ....4-S4 (1) Checking and Adjusting ..............4-S4 (2) Disassembling and Assembling the Hydraulic Control Valve .....4-S5 (3) Disassembling and Assembling the Hydraulic Pump......4-S9 [2] LIFTING LINKAGE.................4-S14 (1) Disassembling and Assembling ............4-S14...
Page 213: Troubleshooting
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page Mower Does Not Rise Control valve malfunctioning Repair or replace 4-S7 Lift cylinder damaged Replace 4-S14 Relief valve spring damaged Replace 4-S7 Relief valve setting pressure too low Adjust 4-S4 Hydraulic pump defective...
Page 214 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 2. SERVICING SPECIFICATIONS Item Factory Specification Allowable Limit Relief Valve (Control Valve) Setting Pressure 5.5 to 7.0 MPa – [at engine speed 56 to 71 kgf/cm ZD321, ZD326 : 800 to 1000 psi 1800 min (rpm) ZD331 : 1600 min...
Page 215 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts : See page G-9.) Item N·m kgf·m lbf·ft Center case front cover mounting screw 40 to 44 4.0 to 4.5 29 to 32...
Page 216: Checking, Disassembling And Servicing
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM 4. CHECKING, DISASSEMBLING AND SERVICING [1] HYDRAULIC CONTROL VALVE, PUMP AND CYLINDER (1) Checking and Adjusting Relief Valve Setting Pressure 1. Remove the plug (2) from the front cover of transmission center case. 2. Install the adaptor (3/8 in., straight thread), cable and pressure gauge.
Page 217: Disassembling And Assembling The Hydraulic Control Valve
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM (2) Disassembling and Assembling the Hydraulic Control Valve Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. •...
Page 218 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM PTO Clutch Link, Cylinder Hose, Oil Cooler Pipe and HST Charge Pipes 1. Remove the seat and seat base assembly. 2. Remove the PTO clutch link (1). 3. Remove the lift rod (2). 4. Disconnect the oil cooler pipe (3). 5.
Page 219 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Lift Shaft and Arm 1. Remove the lift arm (1). 2. Remove the oil seal (3). 3. Remove the internal snap ring (4). 4. Remove the lift shaft (5) with ball bearings and remove the arm (2).
Page 220 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Relief Valve 1. Remove the plug (1), and remove the shims (2), spring (3), poppet (4) and valve seat (5). (When reassembling) • Take care not to damage the O-ring on plug. 49 to 68 N·m Tightening torque Relief valve plug 5.0 to 7.0 kgf·m...
Page 221: Disassembling And Assembling The Hydraulic Pump
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM (3) Disassembling and Assembling the Hydraulic Pump Draining Transmission Fluid CAUTION To avoid personal injury : • Be sure to stop the engine and remove the key before changing or checking the oil. • Allow transmission case to cool down sufficiently; oil can be hot and may cause burns.
Page 222 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Draining Coolant CAUTION • Never open the radiator cap while operating or immediately after stopping. Otherwise, hot water will spout out from the radiator. Wait for more than ten minutes to cool the radiator, before opening the cap.
Page 223 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Bonnet, Fuel Hose, Wiring Harness and Others 1. Remove the snap pin and bonnet mounting screw, then remove the bonnet (3). 2. Disconnect the wiring connectors for engine stop solenoid, glow plug, coolant temperature sensor, engine oil pressure switch and dynamo.
Page 224 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Oil Cooler, Radiator, Universal Joint and Removing Hydraulic Pump 1. Remove the bonnet cover (1) and ROPS connecting plate. 2. Remove the oil cooler (2). 3. Remove the radiator (3). 4. Remove the ROPS connecting plate, under (4). 5.
Page 225 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Hydraulic Pump 1. Remove the hydraulic pump assembly (1). 2. Remove the side plate (2). 3. Remove the drive gear (3) and the driven gear (5) from the casing (4). (When reassembling) • Take care not to damage the O-ring. •...
Page 226: Lifting Linkage
ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM [2] LIFTING LINKAGE (1) Disassembling and Assembling Removing Lift Cylinder 1. Disconnect the cylinder hose (1). 2. Remove the clevis pin (4). 3. Remove the cylinder bracket (2), and remove the bushings. 4. Remove the lift cylinder (3) with cylinder hose (1). (1) Cylinder Hose (3) Lift Cylinder (2) Cylinder Bracket...
Page 227 ZD321, ZD326, ZD331, WSM HYDRAULIC SYSTEM Mower Linkage 1. Remove the clevis pins (5) and horizon plate (2). 2. Remove the front pin (4) and front arm (3). 3. Remove the clevis pin, and disconnect the lift shaft (1) and lift cylinder.
Page 228 ELECTRICAL SYSTEM KiSC issued 04, 2007 A...
Page 229 MECHANISM CONTENTS 1. WIRING DIAGRAM ..................5-M1 2. STARTING SYSTEM ..................5-M2 [1] RELAY ..................... 5-M3 [2] STARTER ....................5-M4 [3] GLOW PLUG ..................5-M5 [4] SAFETY SWITCH ................... 5-M5 [5] FUEL PUMP.................... 5-M6 [6] ENGINE STOP SOLENOID ..............5-M6 3.
Page 230: Wiring Diagram
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 1. WIRING DIAGRAM Coolant Temperature Gauge Fuel Gauge Charge Glow Hour Meter Color of Wiring Oil Lamp Fuel Lamp Lamp Lamp W ....White V .... Violet RY ..Red / Yellow YR ..Yellow / Red E U + E U + HOUR METER...
Page 231: Starting System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 2. STARTING SYSTEM (1) Glow Lamp (6) Starter Relay (10) Starter (14) Safety Switch (LH) (2) Starter Switch (7) Solenoid (11) Glow Plug (15) PTO Switch (3) Harness A (8) Fuse (12) Brake Switch (16) Seat Switch (4) Harness B (9) Slow Blow Fuse...
Page 232: Relay
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [1] RELAY Relay Relay (1) basically consists of relay winding (2) and mechanical contact points (9). Current flowing from switch to relay winding (5) cause “ON (Close)” or “OFF (Open)” of mechanical contact points (9). When current is applied to the winding (energized) (10), a magnetic field pushes the contact lever (8) and normally open terminal is connected.
Page 233: Starter
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [2] STARTER (1) Housing (2) Magnetic Switch (3) Overrunning Clutch (4) Drive Lever (5) Internal Gear (6) Gear Shaft (7) Planetary Gear (8) Armature Shaft (9) Yoke (10) Brush Holder (11) Rear End Holder W1012893 The reduction system is used planetary gears, and the speed of gear shaft (6) is reduced to approximately one fifth of the armature shaft (8).
Page 234: Glow Plug
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [3] GLOW PLUG This plug is a two-material type QGS (Quick Glow System) for quick temperature rise, and has self- controlling function as well as excellent durability. The heater (4) connected in series to the heater (3), which also functions as the resistor, is incorporated in the sheath tube (1) of the super glow plug.
Page 235: Fuel Pump
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [5] FUEL PUMP An electro magnetic fuel pump uses a transistor that causes the pump to start pumping fuel when the main switch is turned to the “ON” position. Therefore, fuel is supplied to the fuel injection pump regardless of engine speed.
Page 236: Charging System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 3. CHARGING SYSTEM (1) Oil Lamp (5) Hour Meter (9) Fuse (12) Dynamo (2) Charge Lamp (6) Coolant Temperature Gauge (10) Slow Blow Fuse (13) Fuel Switch (3) Glow Lamp (7) Fuel Gauge (11) Starter (14) Regulator (4) Fuel Lamp (8) Starter Switch...
Page 237: Ac Dynamo
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [1] AC DYNAMO The dynamo is an 8-8 pole rotating magnet type generator. It is simple in construction, consisting of a stator and rotor. The rotor is made up of eight permanent magnet pole pieces assembled on a shaft and rotates on center stator around...
Page 238: Easy Checker
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [3] EASY CHECKER To check the conditions of tractor easily before and during operation, easy checker combination of lamps on the easy checker board is provided. Indication Items (1) Oil Pressure Lamp When the engine oil pressure is low, this lamp illuminates.
Page 239: Gauges
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 4. GAUGES (1) Coolant Temperature Gauge (4) Harness A (7) Fuel Sensor (10) Slow Blow Fuse (2) Fuel Gauge (5) Harness B (8) Thermo Unit (11) Starter (3) Starter Switch (6) Ground (9) Fuse The fuel quantity and coolant temperature are indicated by the ammeters.
Page 240: Fuel Quantity
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [1] FUEL QUANTITY Fuel Level Sensor The remaining fuel quantity is detected by the fuel level sensor installed in the fuel tank and indicated on the fuel gauge. For detection, a float and a resistor are used. As the float lowers, the resistance of the variable resistor varies.
Page 241 SERVICING CONTENTS 1. TROUBLESHOOTING ..................5-S1 2. SERVICING SPECIFICATIONS ..............5-S3 3. TIGHTENING TORQUES ................5-S4 4. CHECKING, DISASSEMBLING AND SERVICING........5-S5 [1] CHECKING ....................5-S5 (1) Battery....................5-S5 (2) Safety Switches ..................5-S7 (3) Main Switch..................5-S8 (4) Starter ....................5-S9 (5) Glow Plug....................5-S9 (6) Safety Switch ..................5-S10 (7) Fuel Pump..................5-S11 (8) Engine Stop Solenoid ...............5-S11 (9) Charging System ................5-S12...
Page 242 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page All Electrical Battery discharged or defective Recharge or replace G-26 Equipments Do Not Battery positive cable disconnected or Repair or replace 5-S5 Operate improperly connected Battery negative cable disconnected or Repair or replace 5-S5 improperly connected...
Page 243 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM CHARGING SYSTEM Reference Symptom Probable Cause Solution Page Charging Lamp Does Fuse blown (15 A) Replace G-35 Not Light When Main Wiring harness disconnected or improperly Repair or replace – Switch Is Turned ON connected (between main switch AC terminal and panel board, between panel board and dynamo)
Page 244: Servicing Specifications
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 2. SERVICING SPECIFICATIONS Item Factory Specification Allowable Limit Battery Voltage More than 12 V – Potential Less than 0.1 V – Difference Approx. 0.9 Ω Glow Plug Resistance – Starter Commutator O.D. 30.0 mm 29.0 mm 1.181 in.
Page 245 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts : See page G-9.) Item N·m kgf·m lbf·ft Starter (B terminal nut) 5.9 to 11.8 0.6 to 1.2 4.3 to 8.7...
Page 246: Checking, Disassembling And Servicing
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 4. CHECKING, DISASSEMBLING AND SERVICING CAUTION • To avoid accidental short circuit, be sure to attach the positive cable to the positive terminal before the negative cable is attached to the negative terminal. • Never remove the battery cap while the engine is running. •...
Page 247 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Battery Specific Gravity 1. Check the specific gravity of the electrolyte in each cell with a hydrometer. 2. When the electrolyte temperature differs from that at which the hydrometer was calibrated, correct the specific gravity reading following the formula mentioned in (Reference).
Page 248: Safety Switches
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (2) Safety Switches Method of Inspecting Each Control A defective location can be judge by checking function of each safety switch one by one as shown in the table below. (Reference) • Type of Safety Switch Parking Brake Lever …...
Page 249: Main Switch
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (3) Main Switch Main Switch Continuity 1) Main Switch Key at OFF Position 1. Set the main switch OFF position. 2. Measure the resistance with an ohmmeter across the B terminal and the ACC terminal, B terminal and ST terminal, B terminal and G terminal.
Page 250: Starter
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (4) Starter 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 and the leads from the starter.
Page 251: Safety Switch
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Glow Plug Continuity 1. Disconnect the lead from the glow plugs. 2. Measure the resistance with an ohmmeter between the glow plug terminal and the chassis. 3. If 0 ohm is indicated, the screw at the tip of the glow plug and the housing are short-circuited.
Page 252: Fuel Pump
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (7) Fuel Pump Connector Voltage 1. Disconnect the 2P connector from the fuel pump. 2. Turn the main switch key to the “ON” position, and measure the voltage with a voltmeter between the connector terminals. 3.
Page 253: Charging System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (9) Charging System No-load Dynamo Output 1. Disconnect the lead wires from the dynamo. 2. Start the engine and operate the dynamo at the rated speed. 3. Measure the output voltage with a volt meter. 4.
Page 254: Lighting System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (10) Lighting System Charge Lamp (Charging Circuit) 1. Remove the under panel. 2. Disconnect the 6P connector from the regulator after turning the main switch OFF. 3. Turn the main switch ON and connect a jumper lead from the wiring harness connector terminal (Black) to the chassis.
Page 255: Gauges
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Fuel Lamp (Fuel Switch) 1) Switch Continuity 1. Remove the fuel switch from the RH fuel tank. 2. Measure the resistance with an ohmmeter across the sensor terminals. 3. If the reference values are not indicated, the sensor is faulty. Float at not lower- Infinity most position...
Page 256: Cooling System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Coolant Temperature Sensor 1) Lead Terminal Voltage 1. Disconnect the lead from the coolant temperature sensor after turning the main switch OFF. 2. Turn the main switch ON and measure the voltage with a voltmeter across the lead terminal and the chassis.
Page 257 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Coolant Temperature Switch 1. Measure the resistance with an ohmmeter across the switch terminal and the switch body. 2. If 0 ohm is not indicated in the coolant temperature at 194 °C (201 °F) or more, the sensor is faulty. 3.
Page 258 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM Relay (Horn, Solenoid and Starter) 1. Disconnect the connector from relay (6) after turning the main switch off. 2. Remove the relay from bracket. 3. Measure the resistance with an ohmmeter across the terminal 85 (2) to terminal 86 (5), terminal 87 (1) to terminal 87a (3) and terminal 87 (1) to terminal 30 (4).
Page 259: Disassembling And Assembling
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [2] DISASSEMBLING AND ASSEMBLING (1) Starting System (1) Magnetic Switch Mounting (2) Housing (3) Magnetic Switch (4) C Terminal Nut (5) Shaft Assembly (6) Drive Lever (7) Overrunning Clutch (8) Connecting Lead (9) Mounting Screw (10) Armature (11) Yoke (12) Brush Holder...
Page 260: Servicing
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM [3] SERVICING (1) Starting System 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 261 ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM 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. W1023089 Armature Coil 1. Check the continuity across the commutator and armature coil core with an ohmmeter.
Page 262: Charging System
ZD321, ZD326, ZD331, WSM ELECTRICAL SYSTEM (2) Charging System Bearing 1. Check the bearing for smooth rotation. 2. If it does not rotate smoothly, replace it. W1024489 KiSC issued 04, 2007 A 5-S21...
Page 263 ROTARY MOWER KiSC issued 04, 2007 A...
Page 264 MECHANISM CONTENTS 1. POWER TRANSMISSION ................6-M1 KiSC issued 04, 2007 A...
Page 265 ZD321, ZD326, ZD331, WSM ROTARY MOWER 1. POWER TRANSMISSION (1) Center Pulley (3) 21T Bevel Gear (5) Outer Pulley (9) Blade Shaft (2) 16T Bevel Gear (RCK54P-321Z) (6) Mower Belt (10) Outer Blade (RCK54P-321Z) 19T Bevel Gear (7) Center Blade 15T Bevel Gear (RCK60P-331Z) (8) Bevel Gear Shaft...
Page 266 SERVICING CONTENTS 1. TROUBLESHOOTING ..................6-S1 2. SERVICING SPECIFICATIONS ..............6-S2 3. TIGHTENING TORQUES ................6-S3 4. CHECKING, DISASSEMBLING AND ASSEMBLING ........6-S4 [1] CHECKING AND ADJUSTING ...............6-S4 [2] DISASSEMBLING AND ASSEMBLING..........6-S7 KiSC issued 04, 2007 A...
Page 267 ZD321, ZD326, ZD331, WSM ROTARY MOWER 1. TROUBLESHOOTING Reference Symptom Probable Cause Solution Page Blade Does Not Turn PTO system malfunctioning Check transmission – Broken mower belt Replace mower belt G-36 Blade Speed Is Slow Loosen mower belt Replace mower belt G-36 or tension spring Clogged grass...
Page 268 ZD321, ZD326, ZD331, WSM ROTARY MOWER 2. SERVICING SPECIFICATIONS Item Factory Specification Allowable Limit Pinion Shaft (without Mower Belt) Turning Force Less than 117.7 N – 12.0 kgf 26.5 lbf Turning Torque Less than 1.47 N·m – 0.15 kgf·m 1.08 lbf·ft Bevel Gears in Gear Box Backlash 0.1 to 0.2 mm...
Page 269 ZD321, ZD326, ZD331, WSM ROTARY MOWER 3. TIGHTENING TORQUES Tightening torques of screws, bolts and nuts on the table below are especially specified. (For general use screws, bolts and nuts: See page G-9.) Item N·m kgf·m lbf·ft Mower blade screw 98.1 to 117 10.0 to 12.0 72.4 to 86.7...
Page 270 ZD321, ZD326, ZD331, WSM ROTARY MOWER 4. CHECKING, DISASSEMBLING AND ASSEMBLING [1] CHECKING AND ADJUSTING Adjusting Anti-scalp Rollers IMPORTANT • The flattest cut can be achieved by having the anti-scalp rollers adjusted off the ground. Check anti-scalp roller adjustments each time the mower deck cutting height is changed.
Page 271 ZD321, ZD326, ZD331, WSM ROTARY MOWER Adjusting Left and Right Cutting Height 1. Wheel pressure must be correct. 2. Raise up the mower deck to the transport position. (Also the top end). 3. Turn the cutting height set dial (1) to the 3 in. cutting height position.
Page 272 ZD321, ZD326, ZD331, WSM ROTARY MOWER Adjusting Front and Rear Cutting Height 1. Wheel pressure must be correct. 2. Raise up the mower deck to the transport position. (Also the top end). 3. Turn the cutting height set dial (1) to the 3 in. cutting height position.
Page 273 ZD321, ZD326, ZD331, WSM ROTARY MOWER [2] DISASSEMBLING AND ASSEMBLING Universal Joint and Belt Covers 1. Remove the universal joint (1). 2. Remove the left and right belt covers (2), (3). (1) Universal Joint (3) Belt Cover (Right) (2) Belt Cover (Left) W1012580 Mower Blades (Center Blade and Outer Blades) 1.
Page 274 ZD321, ZD326, ZD331, WSM ROTARY MOWER Gear Box and Mower Belt 1. Remove the mower deck from the machine. 2. Remove the left and right hand shield from the mower deck. 3. Clean around the gear box. 4. Remove the belt from the tension pulley. 5.
Page 275 ZD321, ZD326, ZD331, WSM ROTARY MOWER Center Pulley Holder 1. Unscrew the center pulley holder screws (8) and reamer screws (7). 2. Remove the upper oil seal (5) and lower oil seal (12). 3. Remove the internal snap ring (11) and ball bearing (10). (When reassembling) •...
Page 276 ZD321, ZD326, ZD331, WSM ROTARY MOWER Outer Pulley and Blade Shaft 1. Unscrew the outer pulley mounting nut (19), and remove the outer pulley (22) and feather key (18). 2. Unscrew the pulley holder mounting screws (28), and separate the left pulley holder (27) from the mower deck. 3.
Page 277 ZD321, ZD326, ZD331, WSM ROTARY MOWER Turning Torque of Pinion Shaft 1. Remove the mower belt, and reassemble the gear box to the mower deck. 2. Wind a string around the pinion shaft and set a spring balance (or push-pull gauge) to the tip of the string, and then slowly pull the spring balance horizontally to measure the turning force.
Page 278 ZD321, ZD326, ZD331, WSM ROTARY MOWER Backlash between Bevel Gears 1. Remove the gear box cap (3). 2. Place fuses the bevel gear (4) on the pinion shaft (2). 3. Turn the pinion shaft (2). 4. Take out the fuses, and measure the thickness of fuses with an outside micrometer.
Page 279 EDITOR : KUBOTA FARM & INDUSTRIAL MACHINERY SERVICE, LTD. 64, ISHIZU-KITAMACHI, SAKAI-KU, 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 2007. 04, S, EI, EI, e Code No.9Y111-00092 KUBOTA Corporation 2006.

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Kubota WSM ZD321 Workshop Manual

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