Bosch CX gen 4 suddenly no assistance (broken?)

[Pascal K]

A problem suddenly and completely unexpectedly occurred today with my Mondraker Level 2023 with Bosch CX Gen 4. While driving up the mountain, there was suddenly no more pedal assistant and the engine revved up as if it were empty. There wasn't a steep climb or any other cracking noise from which I could have concluded that something has broken. I then tried all driving modes, turned it off and on again, performed a reset, all without success. Luckily nothing blocked so I was at least able to pedal home without motor support. It seems as if a clutch is going empty or, for example, a gear no longer has any teeth and is no longer engaging, but as I said, this happened without notice or any noise. The error code was then on the display - error 523001, which I believe actually points to the speed sensor. I can only imagine that the system was confused because the engine revved up empty but the wheel rotated normally, because when I continued to drive without assistance, the speed was displayed correct. Is there anything else I can try or does the bike have to go to the dealer? It's just not around the corner

 

[bazxa]

Unfortunately it sounds like a dealer job. We can't buy parts,very annoying. There is an English guy that posts and supplies bearing kits he may have some info on his site, Ill re post if I find a link. Good luck

 

[Coldat]

Hey! What was the solution? I've got exactly the same issue...

 

[Hattori-Hanzo]

Also following. Exact same error code and symptoms on mine, zero assistance from the motor but can manually pedal fine.
Hoping it's just a simple speed sensor failure, but mine also had some configuration errors and wouldn't connect to the diagnostic machine, so I'm suspecting mine is a little more serious

 

[Coldat]

Also following. Exact same error code and symptoms on mine, zero assistance from the motor but can manually pedal fine.
Hoping it's just a simple speed sensor failure, but mine also had some configuration errors and wouldn't connect to the diagnostic machine, so I'm suspecting mine is a little more serious

100% its not a speed sensor... This error appears, cause motor starts to assist, but has no connection with cranks. The wheel rotates slowly, while the motor gives all its boost. Thats why when u pedal with motor off - sensor works fine. I suppose the clutch bearring suddenly died...

 

[Mikerb]

I think your assumptions are right. Not on a Bosch cx but on a Levo, my son snapped a chain pedalling uphill on turbo and the motor made a huge noise revving really high for a fee seconds...and he was left with an error which cleared once restarted with a repaired chain. Clearly if you can still pedal albeit with the motor off, the mechanical drivetrain is good but you have lost connection between the motor and cranks. So sounds like a broken sprag/ clutch bearing. Options are a new motor if under warranty or a motor repair if not.

 

[Coldat]

Hope the topicstarter notices all notifications and will help us )

 

[Bearing Man]

Bosch Gen 4: Sudden loss of drive and the motor spinning up and shutting down is normally due to the failure of the sprag bearing within the large steel drive gear.

 

[Coldat]

Found the reason! My clutch was ok and
Peter from Ebike Motor Center recommended me to check one of gears inside the gearbox. They are pressed together, but there is no spline on the gear, also only about 2/3 inside of the gear touches the spline. The inner side got stripped and now it can easily slip. The next is step is to figure out how to connect them together back)

 

[Embt]

Found the reason! My clutch was ok and
Peter from Ebike Motor Center recommended me to check one of gears inside the gearbox. They are pressed together, but there is no spline on the gear, also only about 2/3 inside of the gear touches the spline. The inner side got stripped and now it can easily slip. The next is step is to figure out how to connect them together back)

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Why didn't u take it to dealer

 

[Coldat]

Why didn't u take it to dealer

I’m in Moscow, there is no dealer in here)

 

[RustyIron]

The hole in the gear appears to be damaged and the splines on the hardened shaft appear to be intact. If that is the case, I would first bore the hole bigger in the gear. Make a bushing with a shrink fit. Bore out the bushing to the finish size, press it all together, et voilà, you're back in business.

 

[Coldat]

After some engineering thoughts we finally solved the problem!
We wanted to make a pin, but checked out that in this case the rotation way may unpress the gear again. (If it was opposite - this method could work)
We wanted to make a bushing as above - but to many operations sounded risky.
So, as always WELDING AND ANGLE GRINDER (in this case only welding)
And again my greates thanks to Ebike Motor Center and Peter especially!
Btw, Bosch also replied me... after a month with a question "where r u from"

 

[RustyIron]

Very nice! I don't think that's going to come apart any time soon.