I destroyed my motor by attempting an out of warranty service at home. I know.

[andybobbill]

I know, I know. Let me stop you right there. In my defence I know about electric motors and the repair of, but sometimes life doesn't go to plan.

Once we're past that bit, my motor is f-ed. Magnet rotor damaged and casing cracked. I know what I did and I know not to do it again. However I do need spare parts. Where on earth can I find these things, in the shady underworld of eBay or some backroom forum here??

For reference it's a Bosch Gen 4 Smart System BDU3741 model. I could do without ponying up for a brand new one.
Any advice gladly and sheepishly taken...

 

[irie]

@Bearing Man might have some parts.

 

[Tone461]

I 100% respect your honesty. Some folk on here cant do the basics, its a blow but hopefully this thread will develop into a learning experience for all of us.
As irie said, bearing man is a great bloke and will help you get sorted. He has had three Bosch motors from me and they always come back feeling really nice,
Don't beat yourself up to much, at least you had a go.

 

[Bearing Man]

I know, I know. Let me stop you right there. In my defence I know about electric motors and the repair of, but sometimes life doesn't go to plan.

Once we're past that bit, my motor is f-ed. Magnet rotor damaged and casing cracked. I know what I did and I know not to do it again. However I do need spare parts. Where on earth can I find these things, in the shady underworld of eBay or some backroom forum here??

For reference it's a Bosch Gen 4 Smart System BDU3741 model. I could do without ponying up for a brand new one.
Any advice gladly and sheepishly taken...

This will be an almost impossible fix for you at home. Unfortunately, the armature also holds the motor angle magnet, which is calibrated to the PCB. As the PCB is a "SMART" it cannot be simply swapped out with a gearbox as can be done on the Non smart gen 4.

We can sell you any of the parts you need, no problem. But to be honest, I would let us take a look if the armature is damaged, we may still get a reading from the angle magnet above it and be able to align a new armature to the same motor angle. If we can't fix it, we can offer a part exchange against a new motor. We don't charge for looking either! www.ebikemotorcentre.com

 

[andybobbill]

This will be an almost impossible fix for you at home. Unfortunately, the armature also holds the motor angle magnet, which is calibrated to the PCB. As the PCB is a "SMART" it cannot be simply swapped out with a gearbox as can be done on the Non smart gen 4.

We can sell you any of the parts you need, no problem. But to be honest, I would let us take a look if the armature is damaged, we may still get a reading from the angle magnet above it and be able to align a new armature to the same motor angle. If we can't fix it, we can offer a part exchange against a new motor. We don't charge for looking either! www.ebikemotorcentre.com

Thanks @Bearing Man. At this point I'm quite happy to hand it to somebody that doesn't have my cack-handedness. It's currently almost completely disassembled as I was chasing some rusty looking grease, which I believe I found the source of in the two reducer-gear bearings I've removed. I assume there's no point re-assembling before sending it to you?

 

[Plummet]

My mate did a similar thing. Pulled down his Shimano to replace the bearings as its the right thing to do. He thought he did everything properly, put the motor back together... didnt work....

He is a rotating equipment mechanic too, so he knows his shit......
Those motors are basically a throw away item.

I'm just going to ride my bosch into the ground until it fails then buy a new one like buying a new tooth brush.....

 

[Bearing Man]

Thanks @Bearing Man. At this point I'm quite happy to hand it to somebody that doesn't have my cack-handedness. It's currently almost completely disassembled as I was chasing some rusty looking grease, which I believe I found the source of in the two reducer-gear bearings I've removed. I assume there's no point re-assembling before sending it to you?

No, just put all the bits in a box and send it down. Rest assured you're not the first to do this Just put the PCB back into the case, to keep it protected.

 

[Crawford919]

I know, I know. Let me stop you right there. In my defence I know about electric motors and the repair of, but sometimes life doesn't go to plan.

Once we're past that bit, my motor is f-ed. Magnet rotor damaged and casing cracked. I know what I did and I know not to do it again. However I do need spare parts. Where on earth can I find these things, in the shady underworld of eBay or some backroom forum here??

For reference it's a Bosch Gen 4 Smart System BDU3741 model. I could do without ponying up for a brand new one.
Any advice gladly and sheepishly taken...

I feel your pain. I just spent $900 US on bearings and tools to repair my out of warranty Brose. Was chasing a noise when pedaling at low loads. Got it apart and found a one way bearing that was starting to come apart and replaced it and other bearings and thought I had fixed it for sure. Motor was super clean inside so I felt good about my chances. Got it all back together and it runs and works perfectly but still has the same noise. Oh well I learned a few things I guess.

 

[zizajaun]

Bosch motors come up frequently on ebay.

 

[Bearing Man]

Thanks @Bearing Man. At this point I'm quite happy to hand it to somebody that doesn't have my cack-handedness. It's currently almost completely disassembled as I was chasing some rusty looking grease, which I believe I found the source of in the two reducer-gear bearings I've removed. I assume there's no point re-assembling before sending it to you?

No, just put all the bits in a box and send it down. Rest assured you're not the first to do this Just put the PCB back into the case, to keep it protected.

 

[TQFreak]

This will be an almost impossible fix for you at home. Unfortunately, the armature also holds the motor angle magnet, which is calibrated to the PCB. As the PCB is a "SMART" it cannot be simply swapped out with a gearbox as can be done on the Non smart gen 4.

We can sell you any of the parts you need, no problem. But to be honest, I would let us take a look if the armature is damaged, we may still get a reading from the angle magnet above it and be able to align a new armature to the same motor angle. If we can't fix it, we can offer a part exchange against a new motor. We don't charge for looking either! www.ebikemotorcentre.com

Just replace the damaged parts and install the new INNOTRACE Shrimp controller. And high voltage ability with up to 10 kW of powers is a bonus.

VESC based most power dense controller (INNOTRACE Shrimp for middrive motors)

The archive with the current versions of the motor controller files (KiCAD version 10.0.1), Gerber files, CAD files and firmware files can be downloaded here (updated on 2026-05-08). https://drive.google.com/file/d/1H1cO0Xn0t6IBROoDhhICk7BzORAhWdM1/view?usp=sharing There are two PCBs in...

endless-sphere.com

 

[RustyIron]

Any advice gladly and sheepishly taken...

Before you go beating yourself up too bad, let's put it in perspective. Last week you might have been a dummy because you didn't know anything about the insides of Bosch motors. This week you're smart, because you've seen the insides and learned some things.

The world is filled with regular folks too timid to venture outside the box. All their "knowledge" comes form Tick-Tocks. Their lives are spent wallowing in mediocrity. There are a few others, however, that jump into the unknown and take the big risks necessary to achieve big results. Sometimes we blow it up. When that happens we emerge smarter. Your Bosch Education might have cost you a few extra bucks, but so what? The value of your successes will far outweigh the cost of this minor error. You gotta break a few eggs to make that omelet.

 

[irie]

“The capacity to learn is a gift; the ability to learn is a skill; the willingness to learn is a choice”

A necessary requisite is the ability to admit that one doesn't know everything and to admit that when one is wrong and thus able to learn from mistakes.

 

[Suns_PSD]

I think you're a badass op. Good on you for tackling it.
I tackle things all the time that I don't know what I'm doing and nine out of 10 times it works out. Sometimes you lose though but we're still ahead.