Use one or more of the following differences to confirm your motor variant.

1. Motor Mounting Bolt Pattern

• Gen 4: Uses 3 bolts to mount the motor to the frame.
• Gen 5: Uses 2 bolts for mounting.
  This is a clear and consistent physical difference between the generations, See pictures below

2. Diagnostic Report – Motor ID

• When running a Bosch diagnostic report, the Motor ID (product code) will help identify the motor generation:
  • BDU374Y = Gen 4 motor
  • BDU384Y = Gen 5 motor
    (The ‘Y’ is a placeholder for a digit from 0 to 9, indicating minor version variations.)

3. Product Code Sticker on the Motor

• Most Bosch motors have a product code sticker directly on the motor casing.
• This sticker shows the product code (e.g., BDU3740 or BDU3841), which you can match to the Gen 4 or Gen 5 designation above.
• On some bikes, this sticker is visible without removing the motor, but in other cases, removal may be required.

Using these three methods together ensures accurate identification of Bosch Gen 4 vs Gen 5 motors.

Use one or more of the following differences to confirm your motor variant of the Bosch SX motors:

1. Motor Mounting Bolt Pattern

• All Bosch SX motors use a 2-bolt mounting system, but bolt positions vary by model:
  • BDU3142 & BDU3143:
    Both bolts are located at the top left and top right of the motor — above the crank arm.
  • BDU3144 & BDU3145:
    One bolt is located at the top left and the other at the bottom right, positioned diagonally opposite — with one above and one below the crank arm.

  Quick Check:
  If both bolts are above the crank, it's a BDU3142 or BDU3143.
  If the bolts are diagonally placed, it's a BDU3144 or BDU3145.

  Pictures available below

2. Diagnostic Report – Motor ID

• Running a Bosch diagnostic report will show the motor product code, which identifies the variant:
  • BDU3142
  • BDU3143
  • BDU3144
  • BDU3145

3. Product Code Sticker on the Motor

• Bosch SX motors have a product code sticker located on the motor casing.
• This sticker displays the model number (e.g., BDU3143), which can be used to determine the exact variant.
• In some cases, this sticker is visible without removing the motor, but on certain bikes, motor removal may be necessary.

Using these three methods ensures accurate identification of Bosch SX motor variants.

How to identifying the four main types of Bosch speed sensors used on e-bikes:

1. Magnet Mounted to Rear Disc Brake Rotor

• This setup uses a magnet installed on the rear brake rotor.
• The speed sensor is mounted to the chain stay or frame and detects the magnet as the wheel rotates.
• There are multiple versions of this sensor and magnet, but all work the same way — the exact variant does not matter.

Example image below

2. Magnet Mounted to Rear Wheel Spoke

• This type features a magnet clamped to a rear wheel spoke.
• The sensor is mounted nearby on the chain stay.
• Like the rotor-mounted type, there are different magnet shapes and designs, but all work the same way — the exact variant does not matter.

Example image below

3. Magnet Mounted Around the Valve Stem

• This version includes a large black rectangular magnet that fits around the valve stem on the wheel.
• It is bulky and easy to spot due to its distinctive shape.
• The sensor is located with the Bosch engine

Example image below

4. Hidden Magnet Inside the Rim (Near Valve)

• This setup features a magnet hidden inside the wheel rim, usually bolted near the air valve.
• You won’t see the magnet directly, but you can often detect it using a magnetic object like a screwdriver.
• The sensor is located with the Bosch engine

Example image below

Disc Magnet Speed Sensor

Spoke Magnet Speed Sensor

Magnet on the OUTSIDE of the rim above the air valve