Pedals spinning freely clockwise

[jenia_sid]

Hello. I have an ORBEA WILD FS M20 electric bike. It is equipped with a BOSCH Performance Line CX BDU450CX electric motor. Currently, I have an issue where, approximately every 5 to 10 times during an hour-long ride, the pedals start spinning freely clockwise (without rotating the front chainring) after coasting. I checked and confirmed that this occurs even without using the electric assist (likely a mechanical issue with the motor). Could you please advise me on what I can do to solve this problem? Thank you.

 

[Zimmerframe]

@Bearing Man One for you to advise maybe .. sounds shot .. clockwise is presumably from the drive side and they're not pedalling backwards ...

 

[yorkshire89]

Sprag clutch bearing in the motor possibly.

I thought I had this but it turned out to be the chainring spider teeth rounding/cracking where it attaches to the crank spindle.

 

[jenia_sid]

Sprag clutch bearing in the motor possibly.

I thought I had this but it turned out to be the chainring spider teeth rounding/cracking where it attaches to the crank spindle.

I only have a guess that the problem is inside the motor. The chainring attachment looks solid. What was puzzling is that it only started to manifest after coasting, when I began to pedal again. It was possible to fix it by turning the pedals forward and backward several times.
The initial problems arose when attempting to remove the crankset to replace the chainring. The crankset couldn't be removed (due to the lack of suitable tools). Temporarily, there was no free play in the pedals' backward rotation (the crankset and chainring were turning together), but over time, everything returned to normal.

 

[RustyIron]

The initial problems arose when attempting to remove the crankset to replace the chainring. The crankset couldn't be removed (due to the lack of suitable tools). Temporarily, there was no free play in the pedals' backward rotation (the crankset and chainring were turning together), but over time, everything returned to normal.

This is very different than your initial post. The first post implied that there might be some mysterious problem with the motor. Now the story has changed and you're saying that you worked on it in some way, but failed. Things were not right, then then things were right, and now things aren't right again. There are too many variables and unknowns to diagnose the problem from a brief and incomplete description. You're going to have to take the bike to a shop and have them work on it.

 

[Bearing Man]

I only have a guess that the problem is inside the motor. The chainring attachment looks solid. What was puzzling is that it only started to manifest after coasting, when I began to pedal again. It was possible to fix it by turning the pedals forward and backward several times.
The initial problems arose when attempting to remove the crankset to replace the chainring. The crankset couldn't be removed (due to the lack of suitable tools). Temporarily, there was no free play in the pedals' backward rotation (the crankset and chainring were turning together), but over time, everything returned to normal.

Turn your pedals backwards without the chain moving and you should hear the freewheel ratchet clicking quite loud and crisp. If you can't hear anything, or it sounds soft and muffled, your freewheel sleeve is starting to seize to the rust build-up on your crankshaft. This tends to rust or gum-up the freewheel ratchet so as you coast it gets pushed apart, losing drive. However in most cases, for a while at least, it will return and allow pedal assist again. Eventually it will fail if this is the case.
As Yorkshire89 stated. The other thing that could do this is the sprag bearing. However, in a Gen 4 the sprag bearing will generally work or fail totally.

 

[jenia_sid]

This is very different than your initial post. The first post implied that there might be some mysterious problem with the motor. Now the story has changed and you're saying that you worked on it in some way, but failed. Things were not right, then then things were right, and now things aren't right again. There are too many variables and unknowns to diagnose the problem from a brief and incomplete description. You're going to have to take the bike to a shop and have them work on it.

I agree, it was a mistake to add additional information that might lead astray. The issue remains the same: when rotating the cranks clockwise, they spin without engaging the main gear (it feels like the ratchet in the motor is not meshing). However, if I manually hold the main gear and rotate counterclockwise, I can hear the motor spinning. Unfortunately, there are no suitable bike repair shops in my city, or even in my country. The nearest service center is in another country. That's why I'm trying to understand the cause and attempt to solve it on my own.

 

[jenia_sid]

Turn your pedals backwards without the chain moving and you should hear the freewheel ratchet clicking quite loud and crisp. If you can't hear anything, or it sounds soft and muffled, your freewheel sleeve is starting to seize to the rust build-up on your crankshaft. This tends to rust or gum-up the freewheel ratchet so as you coast it gets pushed apart, losing drive. However in most cases, for a while at least, it will return and allow pedal assist again. Eventually it will fail if this is the case.
As Yorkshire89 stated. The other thing that could do this is the sprag bearing. However, in a Gen 4 the sprag bearing will generally work or fail totally.

I tried to pedal counterclockwise, and I didn't hear the clear sound of the ratchet working; instead, I heard more of a noise coming from the bearings' operation, occasionally resembling a muffled attempt to engage. Based on your words, the issue seems to be related to the freewheel mechanism. Does this mean I need to remove the motor and disassemble it? It's a bit scary, of course...

 

[Bearing Man]

I tried to pedal counterclockwise, and I didn't hear the clear sound of the ratchet working; instead, I heard more of a noise coming from the bearings' operation, occasionally resembling a muffled attempt to engage. Based on your words, the issue seems to be related to the freewheel mechanism. Does this mean I need to remove the motor and disassemble it? It's a bit scary, of course...

Yes, your motor will need to come apart, but I think you're going to find a bit of a mess in there! The only thing is that I am a big fan of people doing their own repairs, but the Bosch Gen 4 is not a motor you really want to be "having a go at" It is easy to break and difficult to repair.
Below are the parts I think that are causing your problem.

 

[jenia_sid]

Yes, your motor will need to come apart, but I think you're going to find a bit of a mess in there! The only thing is that I am a big fan of people doing their own repairs, but the Bosch Gen 4 is not a motor you really want to be "having a go at" It is easy to break and difficult to repair.
Below are the parts I think that are causing your problem.

I used to watch videos on the YouTube channel "The Yorkshire Bike Mechanic" about dismantling the Bosch Gen 4. I decided that if I come to the conclusion that the problem is indeed in the motor and it requires disassembly, I won't attempt to do it myself. Thanks to your photos, it will be easier to explain the possible issue to the bike mechanic and convince them to work on the electric motor since it's a mechanical problem. Thank you so much for your help, and I'll update you once the issue is resolved.

 

[jenia_sid]

Below are the parts I think that are causing your problem.

Unfortunately, I couldn't find a professional who would take up the job, so I had to do it myself. You were absolutely right. In picture 1, there are signs of moisture and dirt on the printed circuit board near the 12V connector. There's a lot of dirt around the bearing in picture 2. And, as you pointed out, there was a stuck ratchet in the subsequent pictures. After cleaning off the dirt and rust, I plan to lubricate everything. Could you please advise on measures that can be taken to prevent such consequences in the future? Perhaps you know where I can purchase a system with the ratchet for the future? Thanks again!

 

[Bearing Man]

Unfortunately, I couldn't find a professional who would take up the job, so I had to do it myself. You were absolutely right. In picture 1, there are signs of moisture and dirt on the printed circuit board near the 12V connector. There's a lot of dirt around the bearing in picture 2. And, as you pointed out, there was a stuck ratchet in the subsequent pictures. After cleaning off the dirt and rust, I plan to lubricate everything. Could you please advise on measures that can be taken to prevent such consequences in the future? Perhaps you know where I can purchase a system with the ratchet for the future? Thanks again!

This will have badly worn the plastic bushes in the freewheel sleeve, so will create a lot of play on the chainring once it's all back together. This play will allow more water to get in between the crankshaft and freewheel sleeve. There is currently nothing you can do to stop this, or the water getting past the bearing shields, other than removing and re-greasing from time to time.
Good luck with your re-assembly.

 

[Stihldog]

A Bosch Gen4 motor rebuild is probably/definitely above my pay-grade. The Yorkshire mechanic makes it look easy, but with lots of caveats.

I have a spare Bosch gen4 sitting in my garage with broken bracket bolts in the casing. I’m still reluctant to replace the drive side casing and damaged brackets. This repair doesn’t seem “too difficult” but I want to make sure I have all the necessary parts on hand.

If I take it apart any further I would likely need additional parts, tools and skills.

 

[Bearing Man]

A Bosch Gen4 motor rebuild is probably/definitely above my pay-grade. The Yorkshire mechanic makes it look easy, but with lots of caveats.

I have a spare Bosch gen4 sitting in my garage with broken bracket bolts in the casing. I’m still reluctant to replace the drive side casing and damaged brackets. This repair doesn’t seem “too difficult” but I want to make sure I have all the necessary parts on hand.

If I take it apart any further I would likely need additional parts, tools and skills.

Be very careful! Leave the non-drive side crankshaft circlip in place, and only remove the larger of the two circlips on the drive side. Then you can safely remove the motor cover without moving the freewheel sleeve and breaking the plastic torque sensor.