[SOLVED] Bafang BBS02 : crackling noise when pedaling : any idea why ?

joowaa

New Member
[EDIT]​
Solved on July 10th : as WilliamT suggested, it was most likely caused by the motor mounting bracket rubbing against the chassis, due to the mounting nut being slightly loose, or the motor having slightly dropped since first install.
At least I reckon. In any case, if you hear the same noise, try tightening the motor assembly to the chassis and giving it another try. If it keeps crackling, try spurting a little WD40 like WilliamT explained, it seems to have worked for him.
Don't go full-conspiracy mode and try to disassemble the motor because you suspect there's a problem with the freewheel like I did 😁
[/EDIT]​

Hello everyone,

Recently, my Bafang BBS02 started making a crackling noise when pedaling with moderate force, even when the motor is off.
  • The crackle always happens at the same spot (right pedal forward, pushing down).
  • It doesn't crackle when using only the throttle, which leads me to believe that something is off with the pedal freewheel.
  • However, I'm quite the newbie at diagnosing bafangs, and I was hoping some of you veterans could help me with your expert ears in case I'm mistaken.
  • I intend on disassembling the motor some time this week to check the freewheel, but any alternative idea on the cause would be quite welcome.

Here's a 50 seconds video I recorded a few days ago to showcase this "crackling".

(link to the YouTube video with clickable timestamps)
See 0:12 to 0:30 for the slow crackle demo
See 0:37 to 0:46 for the regular-speed crackle

Additional notes :
  • ignore the high-pitch screech, it's my rear brake. I maintained it slightly pressed with a rubber band in order to generate a resisting torque that would emulate normal pedaling with some actual load.
  • This motor has done about 1000 km so far, without a hitch.
  • I usually run it at 260 W when cruising, with some spurts at 500 W uphill, way below its rated power.
  • I don't have brake sensors and there's been a few times where I had to suddenly brake as the motor was running.
  • I think it started that one time when I had to brutally brake while launched at 25 km/h. I might have been pedaling at the time, I don't remember.

Thank you for reading, feel free to say whatever comes to mind and have a nice day :)
 
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Thomas Jaszewski

Well-Known Member
Open it up sand inspect the chain ring gear. Some were, just a few, missed in QC. That and many were poorly lubricated. Get some Mobil SCH100 and lubricate ASAP. Who did you purchase from?
 

Thomas Jaszewski

Well-Known Member
I defer to the expert on everything!
Thanks for the warm fuzzy! Having run and supported all of the BBSxx series I am well versed. Ownership from 2014 and tech support from 12/15/2015 through today I just might know a thing or two about the many scores if not hundreds of Bafang motors I’ve sold, repaired, and supported other owners.
Hugs!
 

joowaa

New Member
Hi fellas,

Thank you for your replies and sorry for the long silence and the volume of this post ;) the most pertinent spots are highlighted in bold.
Note to answer Thomas' question: I purchased that motor from the official Bafang seller on Amazon.

I originally planned to disassemble the motor down to the freewheel by replicating this tutorial, but failed at removing the crankshaft seal with my trusty mini-screwdriver-for-tight-spots™.
I might have damaged the seal in the process, but nothing serious I reckon.
By the way, is there even a way of removing that seal without damaging it ? The guy from the tutorial seems to have a pretty easy go at it at 1:05 but I can't figure out if it's because of better tooling or technique.

When I started disassembling, I noticed that the right pedal screw and the bottom bracket lock ring, while still screwed with some tension, came off too easily ; this might be the cause, even though I find it odd that loose parts would cause the system to make that very specific crackle at that very specific pedal position.
I should have stopped there and ran a test but I got curious and wanted to take it apart. Still undecided if I'll try to remove the seal again tomorrow.

The chain ring gearing looked OK and well lubricated. Some specs of dirt made it through the cover and inside the gear chamber, but there doesn't seem to be any dirt between the gear teeth.
I was thinking of adding some generic "for all bearings" bike grease when reassembling.

Hopefully I will be able to run a test tomorrow to see if the crackle is gone when I've cleaned, greased, reassembled, and tightened the whole system.
If it doesn't, then I'll have to consider that it might have been the loose pedal screw, fashion myself a makeshift dunce hat and sit quietly in a corner.


Question in case something needs to be replaced at some point : Does anyone know of a good online Bafang parts seller based in Europe or shipping for a modest fee ? I found california-ebike.com today and will keep searching, but US-based sellers, in general, tend to charge hefty shipping fees.

I'll keep you posted in any case.
Have a nice day :)
 

WilliamT

Active Member
I've had similar crackling noises on my BBSHD when pedaling. I was able to track it down to the motor pressing against the bottom bracket (chain side) causing the noise as the frame flexed. I just sprayed from WD40 between the motor and the bottom bracket and the problem went away.
 

Thomas Jaszewski

Well-Known Member
In the USA There is no official Bafang site in the USA. I’m surprised there’s one theee unless they come from the Polish factory? But the seller should offer a warranty!
We ship a lot of parts to the UK and EU. And it’s the shipping company that gets the fees. I have a reliable UK source. The seal should be replaced. They are cheap

Use blue Loctite or any similar product that does not require heat to remove. Typically the kits ship with blue loctite but it's dubious Chinese quality. A torque wrench is also a good idea. Many bike shops here will torque the nuts for free or a minimal charge.

Mobil SHC100 is lithium-based and compatible with any grease Bafang used. It's specifically formulated for a wide temperature range and electric motors. And recommended by Mobil over clay-based Mobil 28.

Francis Janssen
00447961223451
www.electroncycles.co.uk

ElctronCycles Storage King,
Unit 5 Epsom Trade Park.
Blenheim Road
Epsom
KT19 9DU
United Kingdom.
 
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joowaa

New Member
Alright, I gave up on removing that seal for fear of tearing it, and just cleaned the dirt, re-greased, and reassembled the whole thing well tight.
I gave it a few pedal turns on a static stand and didn't really hear a crackle, but to be sure I'll have to test it with an actual ride. I can't really do it right now (injured knees), maybe next week.

I've had similar crackling noises on my BBSHD when pedaling. I was able to track it down to the motor pressing against the bottom bracket (chain side) causing the noise as the frame flexed. I just sprayed from WD40 between the motor and the bottom bracket and the problem went away.
This makes a lot of sense and it's the most plausible explanation for my problem. Although wouldn't it be better to put grease on the contact area ?
In any case if I hear it crackling again I'll try that WD40 trick (I already put a little after reassembling, just for that sweet aroma).

Thomas > Thanks for the pointers, I'll be sure to check it out.
 

joowaa

New Member
Hello peeps, sorry for the late reply

I tried a few vigorous pedaling spurts across the week and there was no crackling to be heard.
Since the only constructive thing I did was re-mount the motor tighter than before, it looks like it was the bottom bracket like WilliamT suggested. Either a slightly loose nut or a progressive lowering of the motor's resting position across time.

Thanks to everyone for pitching in, I'm marking this thread as solved :)
 

Thomas Jaszewski

Well-Known Member
Check those crank bolts often and use blue loctite. Watch and make certain the motor isn’t up against the frame. On bikes with no motor stabilizer I glue a rubber pad on the frame as a bumper. Most hardware stores will have many choices in pads.
 

joowaa

New Member
Oh right, you meant as a stopper for the radial motion of the motor.
I originally understood it to be a sort of washer between the mounting bracket and the frame, hence my remark on it oughting to be thin (I know 'oughting' isn't a word, but whatever).
Yeah, it makes sense to put a rubber pad there. I already have some padding glued to the frame there that I slightly compressed when mounting the motor ; it should do the trick.
 

Gionnirocket

Well-Known Member
On bikes with no motor stabilizer I glue a rubber pad on the frame as a bumper. Most hardware stores will have many choices in pads.

I did this without reading it here or elsewhere... As I was mounting the motor it just looked like it needed a bumper there.
Great minds think alike 🙃