Bosch Gen4 Motor Repair & Maintenance – Diagnosis + Service
€99.00
Bosch Gen4 Motor Repair & Maintenance
From €99 · Diagnosis & Repair Management
Is your motor making noise, showing play, or displaying an error?
For €99, we handle collection, return shipping, motor opening, and professional diagnosis.
After inspection, we send you real photos of the motor’s condition along with a clear repair quote:
- Complete repair if the motor is damaged (~€300–€380)
- Preventive maintenance if the motor is in good condition (€200–€300)
No obligation: you decide whether to proceed after reviewing the quote.
The initial €99 payment is deducted from the final price.
Is your motor making noise, showing play, or has it already exceeded 10,000 km?
If you notice that the sound of your Bosch Performance Line CX Gen 4 has changed, or the motor has play in the bottom bracket axle, it is very likely that the internal bearings or axle bushings are worn.
Don’t write it off: it can be repaired, and in most cases it ends up performing better than new.
How much does it cost to repair my Bosch Performance Line CX Gen 4?
Most customers contact us with this question: how much does it cost to repair the motor, and is it better to buy a new one?
Every motor is different, but transparency is our priority. Here is a real, side-by-side comparison:
Comparativa de soluciones:
| Feature: | 🔴 New Motor: | 🟢 BiciFix Repair: |
|---|---|---|
| Approximate price: | 780 € – 900 € | 300 € – 380 € |
| Delivery time: | 10-15 days (Each motor must be ordered as a specific spare part for each bike and is shipped from Germany.) | 3 – 4 days (Average repair time after the quote has been approved.) |
| Warranty: | 3 years (Official Bosch warranty.) | 6 months (Warranty covering the repair performed.) |
Billing Example:
This is how the payment process works for a complete repair:
Initial Payment (What you pay today): €99
Includes pickup and delivery management to your home, motor opening, and professional diagnostics.
Second Payment (Upon completion of the repair): ~€250
Paid once the motor is fully repaired and ready to be sent back.
Estimated Final Total: ~€349
(A fast and cost-effective solution!)
What exactly is included in a “Complete Repair”?
Our workshop is known for its technical honesty. In your quote and final invoice, you will see a detailed breakdown of exactly what has been done. This is a standard example of our typical costs:
| ITEM: | Price (VAT included) |
|---|---|
| Specialized work (Includes: disassembly, diagnostics, ultrasonic cleaning, bearing replacement using specialized tools, reassembly, software update, and testing on a test bike.) | 150 € |
| Bearings (It is not necessary to replace all bearings every time.) | 100 – 168 € |
| Seal and gasket kit | 30 € |
| Workshop consumables (Technical greases approved for eBike motors, bearing retainers, and sealants.) | 30 € |
| Estimated total: | 310 € – 378 € |
! Indicative amounts; each motor is quoted individually. It is not always necessary to replace all bearings or all components. The final quote depends on the actual condition of the motor.
Gallery of destroyed motors: Why does the Bosch Gen 4 fail?
This is what happens when water enters through the axle seal. If your motor is making unusual noises, it is, very likely, already in this condition internally. Repairing motors that have reached this state is usually more expensive and more complex, as the axles cannot be replaced (the electronics are calibrated to each specific axle).
In these cases, we provide a custom offer with different options: installing a new motor, or repairing the existing one under the condition that it will not perform like new (motors repaired in this way have already accumulated thousands of kilometers).
That is why we recommend inspecting the motor at the first signs of trouble. In many cases, timely repair prevents the motor from reaching this level of damage.
What is the repair process for a Bosch Gen 4 motor at BiciFix?
- Reception & Digital Testing:
As soon as your package arrives, we connect the motor to our test bench to check the condition of the electronics, sensors, and software version. - Motor Opening:
We open the motor on a clean workbench. We inspect the bearings, axles, bushings, gears, and the main control board. - Report & Quotation:
We send you real photos of what we have found, along with the exact repair quote, via WhatsApp or email. - Repair & Sealing:
If you approve the quote, we replace the necessary parts, lubricate, and reseal the motor. - eturn Shipping:
We carry out a final functional test and send the motor back to you (usually within 24–48 hours after the repair).
Do you have questions before requesting a motor repair?
Contact us via WhatsApp and tell us what is happening with your motor. We will honestly let you know whether this service is the right solution for your case.
Do you prefer to do it yourself? (DIY)
If you are an experienced mechanic, you can purchase the required spare parts from our online shop.
⚠️ Important before opening your motor:
Repairing this motor requires many specific tools and hands-on experience. For example:
- Bearing pullers
- Torx Security bits
- Tool for installing the one-way bearing (sprag bearing)
- Press for bearing installation
- Technical knowledge to avoid damaging the torque sensors or the main control board
- Greases approved for e-bike motors
BiciFix is not responsible for damage caused by improper handling or incorrect repairs.
If you do not have the specific tools or prior experience with this motor, we recommend using our professional workshop service.
Do you have the tools? Buy the spare parts here:
Bosch Gen 4 Maintenance Kit BDU4XX, BDU37YYY
Original price was: €31.99.€29.90Current price is: €29.90.
How Can I Tell If My Motor Is a Bosch Gen 4?
Bosch Gen 4 motors were introduced in 2020. They represent a significant improvement over the previous Gen 2 models, featuring a different internal construction and a magnesium housing.
Visual identification:
They are easy to recognize because they use a standard-sized chainring, unlike Gen 2 motors, which used a very small drive sprocket. They also stand out due to the visible cooling fins on the motor housing.
Commercial Names
-
Bosch Smart System Performance Line CX
-
Performance Line CX (MY2020+)
-
Cargo Line
Model Codes (SKU):
-
Smart System: Bosch BDU3741, BDU3781
-
System 2: Bosch BDU490P, BDU450CX
If your bicycle is from 2020 or later, it most likely uses this motor.
Smart System motors share the same mechanical construction and are also referred to as Gen 4. Visit our Bosch motor generations guide for more information.
Why Is Maintenance Necessary for Bosch Gen 4 Motors?
Although Bosch Gen 4 motors are powerful, they have a critical weak point: the sealing between the bottom bracket shafts.
The original seal is not fully watertight. Over time, if the bearings develop even minimal play, water can penetrate between the shafts. Since the axle is coded to the torque sensor and cannot be replaced separately, water ingress can ultimately force a full motor replacement.
BiciFix recommendation:
We recommend inspecting the motor annually after the first 36 months (or 5,000 km). If any play is detected in the main bearings, they should be replaced immediately to prevent water ingress and save the motor.
Bosch Generation 4 motors (Bosch Gen 4) were introduced to the market in 2020 and have now been in use for several years. Although they are very powerful and reliable motors, they also have certain weaknesses.
One of the most critical weaknesses of the Bosch Gen 4 — and the one that can lead to the most serious consequence, a complete motor replacement — is the seal between the bottom bracket axles. This seal is not fully watertight, and once the bearings develop even a small amount of play, water can enter between the axles, potentially causing severe internal damage to the motor.
This issue is especially serious because the axle is encoded with the torque sensor and cannot be replaced independently.
To prevent this situation, at BiciFix we recommend having the motor inspected annually after the first 36 months from purchase. If any play is detected in the main bearings, even if they still appear to be in acceptable condition, we strongly recommend replacing them to prevent water ingress.
In the images, you can see the condition of an axle from a motor with only 5,000 km of use.
How to Perform Bosch Gen 4 Maintenance
Bosch has released an official maintenance kit that includes the seals covering the main bearings. You can find this kit on our website. The kit comes with an instruction leaflet to carry out the replacement. Be aware that one of the washers can be somewhat difficult to remove.
Unfortunately, our experience shows that this kit alone is not sufficient to prevent motor issues. There is a joint between the axles that allows water to enter the interior of the motor. If water has already entered, the only solution is to open the motor, clean it, and replace at least the main bearings to eliminate the play that facilitates water ingress.
This motor requires many specific tools and a deep understanding of its internal construction. For this reason, we recommend that the repair be carried out by a specialized workshop, such as BiciFix.
What Is the Repair Process for a Bosch Gen 4 Motor at BiciFix?
When we receive the motor, we first connect it to our test bike to check its electronic condition and software status. Next, we open the motor and send you photos and detailed information about the mechanical condition, along with a repair quote. If you approve the quote, we repair the motor, test it again on our test bike, and then ship it back to your address.
Service booking:
You purchase the service on this page and contact us via WhatsApp.
Collection:
We send you the shipping label and arrange the collection of the motor.
Analysis:
We connect the motor to our test bike to verify the electronics and software.
Opening:
We open the motor and inspect the mechanical condition (bearings, moisture, gears).
Final Quote:
We send you photos and the exact cost of the repair.
If you accept:
The amount already paid is deducted from the final total.
If you do not accept:
We return the motor reassembled (the initial payment covers this work).
Are You a Workshop Owner?
We offer special rates and priority service for professionals.
Don’t tie up your workbench with complex motor repairs—outsource them to us and increase your profitability.
| Service |
Cambio de Retenes Bosch Gen 4 ,Presupuesto Revision Completa |
|---|---|
| Reparacion Motores |
Bosch |
Reseñas:
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Rodamientos y Piezas internas
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