Installation Method for Ursus, Zetor, Renault Agriculture Series Starter Motors (12V 3.5KW / 24V 4.5KW)

I. Pre-installation Preparation

1. Tool and Consumable List

2. Safety and Inspection Precautions

• Disconnect Power Supply: Remove the negative (-) cable of the agricultural machinery battery to avoid short circuits during installation.

• Starter Motor Matching Inspection

• Verify the starter motor model: Confirm that the voltage (12V/24V) and power (3.5KW/4.5KW) match the engine model of the agricultural machinery.

• Inspect the starter motor appearance: Ensure the drive gear is free of wear, the housing has no cracks, and the terminals are not corroded.

• Check the mounting holes: The mounting holes on the starter motor flange must fully align with those on the engine flywheel housing.

• Clean the Mounting Surface: Polish the mounting surface of the engine flywheel housing and the starter motor flange with sandpaper to remove oil, rust and impurities, ensuring a tight fit.

II. Installation Steps

1. Starter Motor Positioning and Fixing

1. Orient the drive end of the starter motor toward the engine flywheel, align it with the mounting holes on the flywheel housing, and gently place it into position.

2. Install the locating pin (provided on some models) to prevent displacement of the starter motor, then fit the mounting bolts and lock washers.

3. Tighten the bolts to the specified torque:

• For 12V 3.5KW starter motors: Mounting bolt torque value 25–30 N·m

• For 24V 4.5KW starter motors: Mounting bolt torque value 35–40 N·m

• Note: Use a torque wrench to tighten the bolts evenly diagonally to prevent bolt breakage due to uneven stress.

2. Electrical Circuit Connection

• Main Power Circuit Connection

1. Locate the main terminal on the starter motor (usually marked "+" or "B+", a heavy-duty copper terminal), and connect it to the positive (+) cable of the agricultural machinery battery.

2. Apply conductive paste to the terminal connection, fit the lock nut, and tighten to a torque of 15–20 N·m to ensure good contact without looseness.

• Control Circuit Connection

1. Locate the control terminal on the starter motor solenoid (marked "S" or "50", a small terminal), and connect it to the control wire of the agricultural machinery starter relay.

2. Tighten the control terminal nut to a torque of 5–8 N·m to avoid poor circuit connection.

• Ground Cable Inspection: Confirm that the negative ground cable of the agricultural machinery battery is securely connected to the engine block. Poor grounding will result in weak starter motor performance.

3. Post-installation Review

1. Check the clearance between the starter motor and flywheel: When the drive gear is not engaged, the clearance from the flywheel ring gear should be 2–4mm. If the clearance is too large or too small, adjustments are required (adjustment shims are available for some models).

2. Inspect the cable routing: Ensure all cables are free of twisting and do not come into contact with high-temperature engine components (e.g., exhaust pipes) to prevent wear or high-temperature aging.

3. Reconnect the negative (-) cable of the battery.

III. Post-installation Testing

1. No-load Test: Shift the agricultural machinery into neutral, engage the parking brake, press the start button. The starter motor should run smoothly without abnormal noise or jamming, and the drive gear should engage smoothly.

2. Load Test: Start the engine and observe the starting speed of the starter motor. The engine should start smoothly within 3–5 seconds; after multiple starts, the starter motor housing should not exhibit abnormal heating.

3. Troubleshooting: If issues such as weak starting, abnormal noise or failure to start occur, disconnect the power supply immediately and check whether the circuit connections, torque values and clearances meet the requirements.

Installation Precautions for Ursus, Zetor, Renault Agriculture Series Starter Motors (12V 3.5KW / 24V 4.5KW)

I.Safety Operation Precautions

1. Power Disconnection is Mandatory

   Disconnect the negative (-) battery cable before installation to prevent short circuits that may cause sparks, electrical component burnout, or even electric shock. Wear insulated gloves throughout the installation process to avoid direct contact between hands and metal terminals.

2. Keep Away from High-temperature and Flammable Materials

   Clear flammable liquids such as oil and diesel from the installation area. Avoid proximity to high-temperature components (e.g., exhaust pipes) during starter motor testing to prevent ignition of flammable substances by high temperatures.

3. Prohibit Unauthorized Disassembly

   Do not disassemble the starter motor solenoid or rotor assembly without professional training. Disassembly may cause misalignment of internal components and affect the normal operation of the starter motor.

II.Installation Process Precautions

1. Strict Torque Control

• Mounting Bolt Torque

  For 12V 3.5KW models: 25–30 N·m

  For 24V 4.5KW models: 35–40 N·m

  Use a torque wrench to tighten the bolts evenly in a diagonal sequence. Do not use an extended wrench to apply excessive force, as this may cause bolt thread stripping or starter motor housing deformation.

• Terminal Torque

  Main power terminal: 15–20 N·m

  Control terminal: 5–8 N·m

  Insufficient torque will lead to excessive contact resistance and terminal overheating/burning; excessive torque may damage terminal threads.

2. Thorough Mounting Surface Cleaning

   The mating surfaces of the engine flywheel housing and starter motor flange must be polished with sandpaper to remove rust, oil, and impurities. Failure to do so will result in excessive installation gaps, causing severe vibration during starter motor operation.

3. Mandatory Clearance Inspection

   After securing the starter motor, check the clearance between the drive gear and flywheel ring gear. The standard clearance is 2–4mm. Excessively small clearance may cause gear jamming, while excessively large clearance will lead to engagement impact noise. Adjust the clearance by adding or removing flange shims as needed.

III.Electrical Matching Precautions

1. Strict Voltage Compatibility

   12V starter motors must only be used with 12V power systems, and 24V starter motors with 24V power systems. Cross-voltage installation is strictly prohibited, as it will directly burn out the solenoid coil or rotor winding.

2. Correct Circuit Polarity

   The main power terminal must be connected to the positive battery terminal, and the control terminal to the starter relay output. Reverse connection will cause the starter motor to rotate in the wrong direction, preventing engine cranking and potentially damaging the internal overrunning clutch.

3. Reliable Ground Connection

   The negative battery ground cable must be firmly connected to a rust-free metal surface of the engine block. Poor grounding will result in weak cranking, low rotational speed, and in severe cases, failure to turn the engine flywheel.

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References：

Corresponding Explanation of Key Content and Sources

1. Torque and Clearance Parameters: The mounting bolt torque (25–30 N·m for 12V models, 35–40 N·m for 24V models), terminal torque (15–20 N·m for main terminals, 5–8 N·m for control terminals), and drive gear-flywheel clearance (2–4mm) are all derived from Zetor original technical specifications and Renault installation guidelines.

2. Safety Operation: Requirements such as power disconnection (removing the negative battery terminal), prohibition of cross-voltage installation, and no-load test time limit (≤5 seconds) are mandatory provisions from ISO 16000-2018 and the Ursus service manual.

3. Electrical Matching: The definitions of B+/S terminals and the specifications for ground cable connection are based on the Renault Agriculture electrical system installation guidelines and JB/T 8291-2019.

4. Environmental Adaptation: Requirements for anti-rust agent application and cable fixing with clips are referenced from the contamination protection chapter of ISO 16000-2018 and the Zetor workshop manual.