Gen 4 Rebuild by with pics

[Bearing Man]

Hello. I have same issue. Which type of seal for the torque tube did you use?. I cant find anything that fits well with 21,5mm shaft and 25.5mm tube. My motor is taken apart right now and i basically got everything except the right seal. Tried to fit multiple seals without any good effect unfortunatelly.

This is why something that looks very simple on these motors never is! As @Spiff said, we actually had these seals manufactured. They are also made from a low friction material to stop motor or pedal drag.

 

[mrhaboobi]

any way to remove the back pedal clicking / ratchet noises on the bosch? its the one thing that does drive me nutty

 

[KnollyBro]

This is why something that looks very simple on these motors never is! As @Spiff said, we actually had these seals manufactured. They are also made from a low friction material to stop motor or pedal drag.

Haha... so what you are saying is that a DIY motor rebuild is possible but your results may vary due to the availability of tools, parts and experience? In the end, are these motors pretty good, better than others or great if the rattle and seals are dealt with?

 

[Bearing Man]

The outcome of any rebuild on anything is definitely in the hands of experience. Personally, after what I have seen over the years, I don't really recommend anyone without a sound mechanical background to attempt a motor repair. I do like to see people repairing their own stuff though. I just can't help feeling that some people are best repairing motors, and some repairing socks

The Bosch Gen 4 is a pretty good motor and there are many out there running after many thousands of miles... But the same is true of most motors, and every one of them has an Achilles heal. Some can be made a little better than others.

 

[Andrew426]

any way to remove the back pedal clicking / ratchet noises on the bosch? its the one thing that does drive me nutty

I don't think there is any escaping that short of packing a bunch of grease around the rachet but It wouldn't last long and would potentially make engagement ununreliable. After seeing how narrow the bush is id suggest not backpedalling them if you can avoid it.

 

[Robson]

seals manufactured

Do you sell these seals or do I have to send in my motor?

 

[Bearing Man]

I don't think there is any escaping that short of packing a bunch of grease around the rachet but It wouldn't last long and would potentially make engagement ununreliable. After seeing how narrow the bush is id suggest not backpedalling them if you can avoid it.

The support bushes are the plastic ones. Our metal bush is just to add further longevity to the plastic bushes. So back pedal all you want

 

[Bearing Man]

Do you sell these seals or do I have to send in my motor?

Sorry, we don't sell this seal because the motor must be fully stripped to fit it and a special tool is required. You could contact your local partner here: Where To Buy - eBike Motor Centre (Performance Line Bearings)

 

[Robson]

Sorry, we don't sell this seal because the motor must be fully stripped to fit it and a special tool is required. You could contact your local partner here: Where To Buy - eBike Motor Centre (Performance Line Bearings)

Thanks for the link. Unfortunately they don't seem to be in business anymore. (Smhj investment)
I have 20+ years of mechanical experience and In my work we use all type of seals on daily basis. So manufacturing a tool or stripping the motor won't be an issue. (I believe)
If stripping the motor + the tool is the only reason for not selling the parts could you make an exception in this case?

 

[Bearing Man]

Thanks for the link. Unfortunately they don't seem to be in business anymore. (Smhj investment)
I have 20+ years of mechanical experience and In my work we use all type of seals on daily basis. So manufacturing a tool or stripping the motor won't be an issue. (I believe)
If stripping the motor + the tool is the only reason for not selling the parts could you make an exception in this case?

I did not realise you were in Finland. Sadly I learned that our partner in Finland has recently passed away. His two sons will be taking over the business but they are not up to speed on motors yet.
In this case I would contact our partner in Germany, he will be able to help.
I can't make any exceptions on this because it does not stop there, you will need measurements / drawings, advice. We put so much effort and investment and knowledge into these projects that we can't recoup this if we give away this information. Plus, stripping and tooling are not the only issues, we use some exotic lubricants, demagnetise all major mechanical parts to alleviate code 510 errors etc. I could type for an hour on all the issues we have overcome to perfect this, but you get the point.
I really do understand your frustration, the whole reason I started this business and sell the internal parts etc. is for people to be able to repair their own motors, but in this case, it would definitely cause more issues than it solved.

 

[raficzeqq]

Plastic bushes inside the torque tube are any special too? Igus has a plenty of good bushes i just wonder if somethinbg like that would work.

 

[Stihldog]

Hi Pete. I really appreciate the information you’re able to provide regarding service or repair to these motors. My Bosch GEN4 motor is nearing the end after 10k+ and typical user abuse. (Water, dirt, peddle strikes etc).
I don’t know if the North American market is as big as the EU market? Perhaps the legality of repair is different between the two continents.

I don’t like the idea of throwing a broken motor in the landfill and replacing it with a new one. That seems to be the only option in our area (N.A or BC). Shipping a broken motor to EU for service or repair doesn’t make sense. A service centre in NA , or my region does.

I like the idea of the upgrades and research you’ve invested into these motors. The extent of my service is a bearing seal kit or a drive side casing replacement on a Bosch motor. I won’t, or can’t, go any further than that.

There’s a number of us who are struggling with the cost, in this area, of simply replacing a motor. You may have already suggested a reasonable solution but we have to weigh the costs and logistics.

 

[Bearing Man]

Plastic bushes inside the torque tube are any special too? Igus has a plenty of good bushes i just wonder if somethinbg like that would work.

Yes, these bushes are special, they are extremely hard and self lubricating.

 

[Bearing Man]

Hi Pete. I really appreciate the information you’re able to provide regarding service or repair to these motors. My Bosch GEN4 motor is nearing the end after 10k+ and typical user abuse. (Water, dirt, peddle strikes etc).
I don’t know if the North American market is as big as the EU market? Perhaps the legality of repair is different between the two continents.

I don’t like the idea of throwing a broken motor in the landfill and replacing it with a new one. That seems to be the only option in our area (N.A or BC). Shipping a broken motor to EU for service or repair doesn’t make sense. A service centre in NA , or my region does.

I like the idea of the upgrades and research you’ve invested into these motors. The extent of my service is a bearing seal kit or a drive side casing replacement on a Bosch motor. I won’t, or can’t, go any further than that.

There’s a number of us who are struggling with the cost, in this area, of simply replacing a motor. You may have already suggested a reasonable solution but we have to weigh the costs and logistics.

Thank you for your kind words. I don't think you will have to throw your motor in the bin just yet.
As you probably know, we do have our guys in Tennessee and Québec, so they are on the same continent as you and only about a 2 day ship away. However, there is a lot going on over your side of the pond. I hope to be able to make some announcements early next year.

 

[raficzeqq]

@Bearing Man
I'm wondering about something because my motor is behaving quite strangely. I don't get any assistance, but I can hear the motor working for a couple of seconds before it goes silent. There are no error codes, the clutch is 100% fine, and the walk mode works perfectly. It feels like the magnetoelastic sensor might not be detecting changes in stress on the torque tube. I think there could be three possible causes for this:

1. Plastic Bushings – The old ones were completely worn out, so I replaced them with new bushings. These new ones are much softer, although the manufacturer claims they are widely used in the bicycle industry, even in freewheel applications. Could the softer material be causing less stress on the tube, resulting in the sensor detecting a weaker signal?
2. Crankshaft – The crankshaft was in very poor condition, so I had to remove a small amount of material to restore and polish it, though it was a very minimal amount—much less than 0.1mm.
3. Magnetic Charge on the Tube – If this were the issue, I would expect a 510 error. So why would this lead to a weaker signal rather than a stronger one?

 

[Bearing Man]

@Bearing Man
I'm wondering about something because my motor is behaving quite strangely. I don't get any assistance, but I can hear the motor working for a couple of seconds before it goes silent. There are no error codes, the clutch is 100% fine, and the walk mode works perfectly. It feels like the magnetoelastic sensor might not be detecting changes in stress on the torque tube. I think there could be three possible causes for this:

1. Plastic Bushings – The old ones were completely worn out, so I replaced them with new bushings. These new ones are much softer, although the manufacturer claims they are widely used in the bicycle industry, even in freewheel applications. Could the softer material be causing less stress on the tube, resulting in the sensor detecting a weaker signal?
2. Crankshaft – The crankshaft was in very poor condition, so I had to remove a small amount of material to restore and polish it, though it was a very minimal amount—much less than 0.1mm.
3. Magnetic Charge on the Tube – If this were the issue, I would expect a 510 error. So why would this lead to a weaker signal rather than a stronger one?

I would agree, it would seem the torque sensor is not recognising your input. In answer to your questions:

• Plastic Bushings – The old ones were completely worn out, so I replaced them with new bushings. These new ones are much softer, although the manufacturer claims they are widely used in the bicycle industry, even in freewheel applications. Could the softer material be causing less stress on the tube, resulting in the sensor detecting a weaker signal? The plastic used by Bosch is a very brittle/hard self lubricating high stress enduring type of plastic. Any normal plastics are not usually self lubricating and also breakdown in the presents of most oils and greases. However, this is not what's causing your issue because the torque tube is locked up and will rotate at the same speed as the crankshaft. Therefore the bushes would have no bearing on what the torque sensor sees.
• Crankshaft – The crankshaft was in very poor condition, so I had to remove a small amount of material to restore and polish it, though it was a very minimal amount—much less than 0.1mm. Again, this would not affect the torque tube that surrounds the crankshaft. But this could very well introduce magnetism into the shaft and that can definitely interfere with the magneto-elastic torque sensor. In fact any magnetism introduced into the steel drive gear, torque tube, crankshaft, ratchet and spring can cause havoc.
• Magnetic Charge on the Tube – If this were the issue, I would expect a 510 error. So why would this lead to a weaker signal rather than a stronger one? Please see my answer above. The disruptive magnetic signal can come from any direction, some times they will error with 510, sometimes the motor will stutter but not error, some times it will take off on its own and no error, and sometimes it won't to anything. I would completely strip the motor and demagnetise everything. Do not use magnetic or magnetized tools either.

 

[raficzeqq]

I would agree, it would seem the torque sensor is not recognising your input. In answer to your questions:

• Plastic Bushings – The old ones were completely worn out, so I replaced them with new bushings. These new ones are much softer, although the manufacturer claims they are widely used in the bicycle industry, even in freewheel applications. Could the softer material be causing less stress on the tube, resulting in the sensor detecting a weaker signal? The plastic used by Bosch is a very brittle/hard self lubricating high stress enduring type of plastic. Any normal plastics are not usually self lubricating and also breakdown in the presents of most oils and greases. However, this is not what's causing your issue because the torque tube is locked up and will rotate at the same speed as the crankshaft. Therefore the bushes would have no bearing on what the torque sensor sees.
• Crankshaft – The crankshaft was in very poor condition, so I had to remove a small amount of material to restore and polish it, though it was a very minimal amount—much less than 0.1mm. Again, this would not affect the torque tube that surrounds the crankshaft. But this could very well introduce magnetism into the shaft and that can definitely interfere with the magneto-elastic torque sensor. In fact any magnetism introduced into the steel drive gear, torque tube, crankshaft, ratchet and spring can cause havoc.
• Magnetic Charge on the Tube – If this were the issue, I would expect a 510 error. So why would this lead to a weaker signal rather than a stronger one? Please see my answer above. The disruptive magnetic signal can come from any direction, some times they will error with 510, sometimes the motor will stutter but not error, some times it will take off on its own and no error, and sometimes it won't to anything. I would completely strip the motor and demagnetise everything. Do not use magnetic or magnetized tools either.

Thank you! I’ll give this a try. It’s also possible that the sensor itself is damaged. I doubt there’s any built-in protection or indicator to specifically identify sensor failure, as opposed to issues with other components. The only real way to find a solution is probably to troubleshoot everything else first and see what happens. If that doesn’t work, then something might be wrong with the sensor itself.

 

[Andrew426]

Thank you! I’ll give this a try. It’s also possible that the sensor itself is damaged. I doubt there’s any built-in protection or indicator to specifically identify sensor failure, as opposed to issues with other components. The only real way to find a solution is probably to troubleshoot everything else first and see what happens. If that doesn’t work, then something might be wrong with the sensor itself.

Is the plastic pole wheel that clips over the torque tube seated properly?

 

[Bearing Man]

Thank you! I’ll give this a try. It’s also possible that the sensor itself is damaged. I doubt there’s any built-in protection or indicator to specifically identify sensor failure, as opposed to issues with other components. The only real way to find a solution is probably to troubleshoot everything else first and see what happens. If that doesn’t work, then something might be wrong with the sensor itself.

The electronics are fairly robust, so unless they get wet, the sensors are usually good. However, there is a photo cell cadence sensor on the bottom of the torque sensor. This registers the movement of the cadence cage (reluctor ring if you prefer) attached to the crankshaft. If this sensor is dirty, it will not see the movement of the crankshaft, and won't know that the motor wants power. It won't give a code either. Might be worth a look and a quick clean of the pickup.

 

[raficzeqq]

I believe the encoder is fine now. I had significant issues with it earlier. It somehow got damaged and wouldn’t work properly, even after cleaning, displaying error 513. The chain was also jumping, and the bike behaved as if it was on throttle. Upon closer inspection under a microscope, I noticed that the emitter inside was displaced. I ordered a replacement, soldered it onto the PCB, and initially worried it might cause issues, but I doubt that now.

The sensor is completely new, and I even contacted the manufacturer, who assured me that all sensors, even those from different batches, are identical. Since it’s a digital sensor, it doesn’t require any calibration or adjustments, so I’m confident that replacing it was the correct approach.

Recently, I installed the old bushing and tested how the bike behaves with just one bushing inside the tube (as I only had one functional bushing left; the other was completely damaged). During the test, the bike provided assistance, which led me to suspect that the bushings might be causing some issues. However, I now believe the problem was due to the excessive play in the crankshaft, which caused inconsistent input and triggered the assistance.

 

[Stihldog]

Hi Pete. I’m in the process of removing and shipping my Bosch 2020 gen4 CX motor to CycloChrome in Gaspe/Hull Que.

Juan has suggested the new rebuild kit available from you (New style bearings etc) and will install those during the rebuild/service.

My question is;
Will this new bearing(s) kit also reduce or eliminate the notorious motor rattle? I think I read in one of your posts that this has been addressed by you. Does this require a separate part or is it included with the new bearing kit?
TIA, Cheers

 

[Bearing Man]

Hi Pete. I’m in the process of removing and shipping my Bosch 2020 gen4 CX motor to CycloChrome in Gaspe/Hull Que.

Juan has suggested the new rebuild kit available from you (New style bearings etc) and will install those during the rebuild/service.

My question is;
Will this new bearing(s) kit also reduce or eliminate the notorious motor rattle? I think I read in one of your posts that this has been addressed by you. Does this require a separate part or is it included with the new bearing kit?
TIA, Cheers

The answer is:
No... The motor "rattle" is caused by backlash in the gears and sprag bearing. Our new upgrade for this motor takes the play from the crankshaft and adds a tone of water resistance to some of the most sensitive parts.

 

[Stihldog]

The answer is:
No... The motor "rattle" is caused by backlash in the gears and sprag bearing. Our new upgrade for this motor takes the play from the crankshaft and adds a tone of water resistance to some of the most sensitive parts.

Ok, thanks for the reply.
I’ll forward this response to Juan Carlos at CycloChrome, in Que, and see if they are able to address this issue at the same time as a rebuild.

Btw, the rattle doesn’t bother me. It’s just a noise that I was concerned about.

 

[raficzeqq]

@Bearing Man, I can’t believe it, but it worked! I ordered a cheap demagnetizer from Amazon, and it did the job. The bike feels brand new! Who would have thought that grinding down and polishing the shaft could introduce enough magnetism to disrupt the sensor? Thank you so much for the knowledge you share with everyone; it’s truly amazing.

One quick question—should the ratchet be greased in some way? I’m wondering because, theoretically, it seems like it should be greased since it’s two metal parts. But then again, the grease could potentially run onto the bushings.

 

[Bearing Man]

We do use a very thin smear of white grease on the ratchet. More to damp it a little than anything else. Thanks for the coffee by the way! Much appreciated.