Repairing a Bosch e-bike motor: which parts exist for which generation

Yes, a Bosch e-bike motor can be repaired: bearings, freewheels and seals are available as single parts and as a repair kit. Bosch itself, however, provides for repairs only at an authorised bicycle dealer and with original parts. This guide tells you what Bosch's manuals say and which parts we stock for which generation.

What Bosch writes about opening the motor

The operating instructions for the 3rd and 4th generation (BDU310, BDU350, BDU365, BDU450 CX, BDU490P) say that you must not open the drive unit and that it may only be repaired by an authorised bicycle dealer using original spare parts. They add that the warranty claim lapses if the drive unit is opened without authorisation. The instructions for the 2nd generation and the Smart System (BDU374x) say the same and name qualified specialists.

If your bike is still covered by statutory warranty or a guarantee, go to your dealer first. For service and repairs, Bosch refers you to an authorised bicycle dealer.

First identify the generation

Which parts fit depends on the generation. What counts is the type designation on the motor housing, which starts with BDU:

• BDU250C, BDU255C, BDU250P, BDU290P, BDU250P CX: 2nd generation (Active Line, Performance Line, Performance Line CX).
• BDU310, BDU350, BDU365: 3rd generation (Active Line, Active Line Plus, Performance Line).
• BDU450 CX, BDU490P: 4th generation (Performance Line CX, Performance Line Speed, Cargo Line).

How to find the designation is explained in our guide Bosch e-bike motor: identify the generation and find the right spare parts. If your motor has a four-digit designation such as BDU3740, it belongs to the Smart System. In that case compare the exact designation with the fitment on the product page before you order.

Parts suitable for Bosch Gen2 (BDU2xx)

• Motor repair kit, suitable for Bosch Gen2, €159.95: 14 parts, including the large main bearing on the right, both crankshaft bearings, two needle bearings, two drawn cup roller clutches, three deep groove ball bearings, three O-rings and the shim for the crankshaft.
• Repair kit main bearing and crankshaft bearings, suitable for Bosch Gen2, €59.95: the main bearing on the right, both crankshaft bearings and three O-rings.
• Main bearing right, suitable for Bosch Gen2, €19.95, plus the press-in tool for the main bearing (€24.95).
• PLUS add-on pack, suitable for Bosch Gen2, €74.95: four bearings and two O-rings.
• Damping foil set, suitable for Bosch Gen2, €19.95: four foils between motor and frame.

Parts suitable for Bosch Gen3 (BDU3xx)

• Crankshaft bearing PLB30521, suitable for Bosch Gen3, €24.95: one deep groove ball bearing for the left or right side of the crankshaft.

We do not stock a complete repair kit for the 3rd generation.

Parts suitable for Bosch Gen4 (BDU450 CX, BDU490P)

• Motor Service Kit, suitable for Bosch Gen4, €159.95: five deep groove ball bearings, two drawn cup roller clutches, one sprag clutch and four O-rings.
• Crankshaft bearing PLB40521, suitable for Bosch Gen4, €24.95.
• Crank freewheel PLB40528, suitable for Bosch Gen4, €54.95.

For the Classic Line (DU25, DU45) there is the crankshaft bearing, suitable for Bosch Classic Line, €24.95. All prices at bikely, as of 15 October 2026.

What you should know before buying

• The parts are not original Bosch parts. What exactly is supplied and by which manufacturer is stated on each product page.
• Which part inside the motor is worn only shows once the motor is open. A noise alone does not prove bearing damage. How to rule out other causes first is explained in the guide E-bike motor clicking or grinding? Causes and repair instead of replacement.
• Fitting is a job for a workshop that overhauls e-bike motors. We sell the parts, we do not fit them.
• To undo the lock ring on the chainring you need a special tool: suitable for Bosch Gen2 (€24.95), suitable for Bosch Gen3 (€29.95), suitable for Bosch Gen4 (€29.95).

What Bosch says about care

According to the manuals, no component, including the drive unit, may be immersed in water or cleaned with pressurised water. Bosch advises having the eBike checked technically at least once a year, including the mechanics and the version of the system software. Chainring and pedals should only be replaced with identical parts or parts approved by the bicycle manufacturer.

More guides: How much does an e-bike motor repair cost? Bearings, belt, freewheel or replacement motor compared · Bosch Performance Line CX rattling or clacking: normal or a defect?

Matching parts: Bosch Gen2 · Bosch Gen3 · Bosch Gen4 · Bearing sets and service kits

Sources: Bosch operating instructions for the drive units BDU2xx, BDU3xx, BDU4xx, BDU374x. Read on 12 October 2026.