Introduction
This manual provides essential information for the safe and efficient operation, maintenance, and troubleshooting of your Kubota RK125 Water Cooled 4 Stroke Single Cylinder Diesel Engine. Please read this manual thoroughly before operating the engine and keep it for future reference.
Technical Specifications
The following table details the technical specifications for the RK125 diesel engine (corresponding to model 125DI in the specification chart).
| Parameter | Specification (125DI) | Unit |
|---|---|---|
| Bore x Stroke | 94x96 | mm |
| Displacement | 666 | cc |
| Maximum Power / Speed | 12.5 (9.19) / 2400 | Hp (kW) / rpm |
| Continuous Rated Output / Speed | 11 (8.09) / 2400 | Hp (kW) / rpm |
| Rated Speed | 2400 | rpm |
| Idle Speed | ≤600 | rpm |
| Compression Ratio | 18.01 | |
| Maximum Torque | 4.7 / 1600 | kgf·m / rpm |
| Valve Clearance (cold engine) | 0.195-0.235 | mm |
| Governor System | Flying hammer centrifugal speed type | |
| Fuel Injection Pressure | 190-210 | kgf/cm² |
| Fuel Delivery Position | 17°-19° | |
| Combustion System | Direct injection system | |
| Lubricating System | Forced Lubricating with Trochoid Pump | |
| Lubricating Oil | API CF line SAE 40 (SAE 40 API CF) | |
| Fuel Type | Light diesel (SAE No.2-D) | |
| Fuel Tank Capacity | 11 | L |
| Cooling Water Capacity | 2.1 | L |
| Crankcase Oil Capacity | 2.8 | L |
| Starting System | Speed Doubling Handle by Hand / Electric Start | |
| Direction of Rotation | Counterclockwise Facing Flywheel | |
| Lamp | 12V 35W/35W | |
| Dimension (L*W*H) | 820x348x560 | mm |
| Net Weight | 114 | kg |
Setup and Installation
Proper installation is crucial for the engine's performance and longevity. Ensure all safety precautions are followed during setup.
- Unpacking: Carefully remove the engine from its packaging. Inspect for any damage during transit. Refer to the packaging image for typical component presentation.
Figure 3: Example of packaged engine components - Mounting: Securely mount the engine on a stable, level surface capable of supporting its weight and vibrations during operation. Ensure adequate ventilation around the engine.
- Fuel System Connection: Connect the fuel lines to the fuel tank and engine, ensuring all connections are tight to prevent leaks. Use only Light Diesel (SAE No.2-D). The fuel tank capacity is 11 liters.
- Cooling System: Fill the cooling system with the appropriate coolant. The cooling water capacity is 2.1 liters. Ensure the radiator is clear of obstructions.
- Lubrication System: Fill the crankcase with API CF line SAE 40 lubricating oil. The crankcase oil capacity is 2.8 liters. Check oil levels before initial start-up.
- Electrical Connections (if applicable): For electric start models, connect the battery according to the wiring diagram (not provided, refer to specific electrical manual if available). Ensure correct polarity. The lamp is 12V 35W/35W.
Operation
Follow these steps for safe and effective engine operation.
- Pre-Start Checks:
- Verify fuel level and type.
- Check engine oil level.
- Ensure cooling water level is adequate.
- Inspect all connections for leaks.
- Confirm no obstructions around moving parts.
- Starting the Engine: The engine can be started by hand (Speed Doubling Handle) or electric start.
- Hand Start: Engage the speed doubling handle and follow the manufacturer's specific procedure for manual cranking.
- Electric Start: Turn the ignition key or press the start button. Do not crank for more than 10 seconds at a time to prevent battery drain and starter motor damage.
- Warm-up: Allow the engine to warm up at idle speed (approximately ≤600 rpm) for a few minutes before applying load.
- Operating Speed: The rated speed for continuous operation is 2400 rpm. Avoid prolonged operation at maximum power (12.5 Hp) or continuous rated output (11 Hp) without proper cooling and load management.
- Shutting Down: Reduce engine speed to idle and allow it to cool down for a few minutes before turning off the ignition.
Maintenance
Regular maintenance ensures optimal performance and extends the lifespan of your engine. Refer to the image below for common engine components that may require inspection or replacement.
- Daily Checks:
- Check engine oil level and coolant level.
- Inspect for any visible leaks (fuel, oil, coolant).
- Ensure air filter is clean.
- Every 50 Hours / Weekly:
- Clean air filter.
- Check battery electrolyte level (if applicable).
- Inspect fan belt tension.
- Every 200 Hours / Monthly:
- Change engine oil and oil filter.
- Replace fuel filter.
- Check valve clearance (0.195-0.235 mm cold engine).
- Inspect fuel injection pressure (190-210 kgf/cm²).
- Every 500 Hours / Annually:
- Clean fuel tank.
- Replace air filter element.
- Inspect and clean cooling system.
- Check and adjust fuel injection timing.
- Component Replacement: Use genuine Kubota parts or equivalent for replacements, such as cylinder heads, pistons, cylinder liners, water pumps, solenoid valves, overhaul kits, turbos, and crankshafts.
Troubleshooting
This section provides solutions to common issues you might encounter with your RK125 engine.
| Problem | Possible Cause | Solution |
|---|---|---|
| Engine fails to start | No fuel, low battery (electric start), clogged fuel filter, air in fuel system. | Check fuel level, charge/replace battery, replace fuel filter, bleed fuel system. |
| Engine runs rough or stalls | Clogged fuel filter, dirty air filter, incorrect fuel injection timing, low quality fuel. | Replace fuel filter, clean/replace air filter, check injection timing, use recommended fuel. |
| Overheating | Low coolant level, clogged radiator, faulty water pump, loose fan belt. | Top up coolant, clean radiator, inspect/replace water pump, adjust fan belt tension. |
| Excessive smoke | Incorrect fuel injection, worn piston rings, incorrect oil level/type. | Check fuel injection system, inspect engine components, verify oil specifications. |
If the problem persists after attempting these solutions, please contact qualified service personnel.
User Tips
- Always ensure you have the correct model and part number when ordering replacement parts to guarantee compatibility.
- Regularly check all fluid levels (fuel, oil, coolant) before each use to prevent unexpected shutdowns or damage.
- Keep the engine clean, especially the cooling fins and air intake, to maintain optimal operating temperature.
Warranty Information
This Kubota RK125 engine comes with a 1 Year Warranty. The warranty covers core components of the engine. For specific terms and conditions, please refer to your purchase documentation or contact the seller.
Support and Contact
For technical assistance, parts inquiries, or any other support needs, please contact the seller directly. When contacting support, please have your engine model (RK125) and any relevant part numbers ready.
Seller Contact Information:
- WhatsApp: +86 15576650740
- Email: 1434250503@qq.com
- WeChat: 15576650740
The seller is based in Zhejiang, China, and has been operating since 2012, specializing in OEM and ODM products with a focus on quality and timely delivery.
