Part of the Kubota Repair Manuals.
Brake trouble, a transaxle fault or a front axle problem each has its own troubleshooting section in this 333-page Kubota GR2120 service manual PDF, written for the GR2120 and GR2120-AU lawn tractors. Wiring diagrams trace the tractor's electrical circuits, while hydraulic schematics follow the hydraulic circuit through the steering controller and the mower lift cylinder. Engine, brake and front axle chapters carry their own servicing specifications, and the general chapter lists lubricants, special tools and the maintenance check list. Replace the fuel filter element every 200 hrs. Check the fuel lines every 6 months, and torque the cylinder head screws to 38 to 42 N-m. If you are setting front wheel alignment or adjusting the brake pedal, each job has its own chapter. Download the PDF, use the bookmarks to reach the PTO clutch or mower blade maintenance pages, and search the text layer when you need a spec by name.
What's Inside This Kubota GR2120, GR2120-AU Manual
| System | Pages | Key Topics |
|---|---|---|
| Safety First | 6-8 | Before You Start Service, Operate Safely |
| Safety Decals | 9-11 | Care of Danger Warning and Caution Labels |
| Specifications | 12-13 | Engine Specifications |
| General | 15-80 | Identification, General Precautions, Lubricants, Maintenance Check List, Special Tools, Implement Limitations |
| Engine | 81-139 | Engine Body, Lubricating System, Cooling System, Fuel System, Troubleshooting, Servicing Specifications |
| Transaxle | 140-206 | Travelling System, Hydraulic Transmission, Glide Steer Section, Front Wheel Drive, PTO Clutch, Troubleshooting |
| Brakes | 207-219 | Brake Mechanism, Troubleshooting, Servicing Specifications, Brake Pedal Adjustment, Brake Assembly |
| Front Axle | 220-237 | Front Axle Structure, Troubleshooting, Servicing Specifications, Front Wheel Alignment, Differential Gear Assembly |
| Steering, Hydraulic System, and Mower | 238-333 | Steering Controller, Hydraulic Circuit, Mower Lift Cylinder, Mower Linkage, Power Transmission, Mower Blade Maintenance |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Fuel filter element replacement interval | every 200 hrs | p. 28 |
| Fuel line check interval | every 6 months | p. 28 |
| Cylinder head screw | 38 to 42 N-m | p. 97 |
| Main bearing case screw 2 | 27 to 30 N-m | p. 122 |
| Glide Steer angle | 0.35 rad (22°) | p. 171 |
| Rear shaft nut torque | 40 N·m (4.1 kgf·m, 30 lbf·ft) | p. 162 |
| Brake assembly mounting bolt torque | 7.8 to 8.8 N-m (0.80 to 0.89 kgf-m, 5.8 to 6.4 lbf-ft) | p. 162 |
| Hydraulic PTO clutch assembly mounting bolt | 18 to 20 N·m | p. 187 |
| PTO clutch piston lock nut | 9.8 to 11 N·m | p. 162 |
| Center section mounting hex. socket head screw | 18 to 20 N·m | p. 185 |
| By-pass valve plug | 15.0 N·m | p. 185 |
| Brake Pedal Free Travel | 15 to 25 mm (0.59 to 0.98 in.) | p. 212 |
Kubota GR2120, GR2120-AU Common Problems This Manual Covers
Kubota GR2120 coolant low or radiator fins clogged with dust and engine running overheated
Check coolant and engine oil with the engine stopped and key removed (page 38). Never remove the radiator cap while running or right after shutdown; loosen it slowly to release pressure (page 7). Fill insufficient coolant (the radiator holds 2.1 L per page 12). Clean dust from the radiator net and fins, adjust or replace the fan belt, and replace a damaged radiator cap or hose.
Manual Section: Engine Troubleshooting p. 91Hydrostatic transaxle under excessive machine load with oil overheating and losing power
Check HST oil level and fill to the proper level; the hydrostatic transmission holds 3.3 L per page 12. Replace a clogged oil filter cartridge, since it drops charge pressure, and reduce machine load. If heat and power loss continue, replace the HST relief valve or hydraulic pump per page 159, and release pressure before you disconnect any hydraulic line (page 7).
Manual Section: Transaxle Troubleshooting p. 159Transaxle bevel gear section with excessive or unusual noise at all times or while turning
Check transmission fluid level and type with the machine on level ground, engine off, key removed and parking brake set (page 35). Fill or change the fluid if it is insufficient or the wrong type. Adjust backlash between the 11T bevel gear and 17T-13T gear shaft, and replace worn bearings, the cause the bevel gear chart on page 160 lists for noise while turning.
Manual Section: Transaxle Troubleshooting p. 160Brake shoe worn or brake pedal free travel excessive with insufficient braking force
Measure brake pedal free travel with the engine stopped and the key removed (page 214). Adjust it to 15 to 25 mm (0.59 to 0.98 in.) per page 212. If braking force is still weak, inspect the brake shoes and brake drum; replace worn parts, and replace any brake shoe contaminated with grease or oil.
Manual Section: Brake Troubleshooting p. 211Mower lift system with mower not rising, not lowering, or dropping by its own weight
Check transmission oil level and refill if low, then clean or replace a clogged oil strainer. Test main relief valve setting pressure against 9.50 to 11.0 MPa (page 271); adjust if low or replace a damaged relief valve spring. Release pressure before you disconnect hydraulic lines (page 7). If the mower drops by its weight, replace the worn lift cylinder or faulty control valve.
Manual Section: Hydraulic System Troubleshooting p. 270Mower PTO clutch with worn friction plate or brake plate that slips or drags
Inspect the PTO clutch valve first: low operating pressure from a malfunctioning valve makes the clutch slip, so replace it. Replace excessively worn clutch discs or friction plates. For drag, replace a worn or deformed brake plate and a weak or broken clutch spring. Torque the hydraulic PTO clutch assembly mounting bolts to 18 to 20 N·m per page 187.
Manual Section: Transaxle Troubleshooting p. 160Frequently Asked Questions
Why does my Kubota GR2120 stall when engaging the PTO?
Stalling when engaging the PTO is often related to the Operator Presence Control (OPC) system. If the operator stands up while the PTO is engaged, the engine will shut off. Ensure you are seated in the operator's seat during all tests and operation. If the engine stalls under other conditions, check the PTO control system as described on page 43. p. 42
Why will the Kubota GR2120 mower deck not stay raised?
If the mower deck will not stay raised, it may be due to a problem with the hydraulic lift system. Check the mower lift cylinder for damage or the control valve for malfunctioning. If the mower drops by its own weight, the lift cylinder may be worn or damaged, requiring replacement as specified on page 270. p. 270
What is the engine oil capacity for the Kubota GR2120?
The engine oil capacity for the GR2120 is 2.8 L (3.0 U.S. qts, 2.5 Imp. qts). Always check the oil level using the dipstick and ensure it is between the upper and lower levels. p. 12
What is the tightening torque for the cylinder head screws on the GR2120 engine?
The tightening torque for the cylinder head screws is 38 to 42 N-m (3.8 to 4.3 kgf-m, 28 to 31 lbf-ft). Apply engine oil to the threads and seats before tightening. p. 97
How often should the transmission fluid be changed on the GR2120?
The transmission fluid should be changed every 400 hours of operation. Ensure the machine is on level ground and the mower is lifted up when checking the oil level. p. 33
How will I receive this Kubota GR2120 Service Manual?
A 333-page Service Manual in searchable PDF format, available the moment you complete checkout. View on computer, tablet, or phone, with no shipping wait.
Can I print a copy of this Kubota GR2120 Service Manual for the shop?
Yes. Print the pages or sections you need for your own shop use. Any standard printer works.
