Clunking Noise in Bafang BBSHD

[JMOTO]

Bafang BBSHD
Purchased: March, 2021 (factory installed)
Mileage: 5932 (7/17/24)
Clunking or knocking noise coming from the crank area. This just started in roughly the last 1000 miles. The Bafang chainring gear has been greased (I've done this about every 1200 miles), pedals swapped out, crankarms retorqued, inner M33 left lockring torqued to 90Nm. The noise is intermittent but usually occurring when the left crankarm nears the bottom of the stroke. On a rare occasion I have also heard the noise when the right crankarms starts the downstroke. The volume of the knock varies from barely audible to quite loud. The noise can occur with and without pedal assist, loudest when climbing steep hills. Sometimes the noise will go away after starting up from a stop or start up after a stop. Other times it will come and go while riding. I have not done enough testing with the throttle only to determine if it will make the noise under that condition. The chain and chainring have recently been replaced (a couple of 100 miles ago). The noise was also present before their replacement. Ideas?

 

[A-DamW]

I found this thread describing something similar, the videos below are from the first post, does it sound like your issue?

This sounds like a slipping roller clutch to me(A-DamW)

Under throttle:

Double knock:

Double and single knock with PAS & throttle:

 

[Guerney]

Bafang BBSHD
Purchased: March, 2021 (factory installed)
Mileage: 5932 (7/17/24)
Clunking or knocking noise coming from the crank area. This just started in roughly the last 1000 miles. The Bafang chainring gear has been greased (I've done this about every 1200 miles), pedals swapped out, crankarms retorqued, inner M33 left lockring torqued to 90Nm. The noise is intermittent but usually occurring when the left crankarm nears the bottom of the stroke. On a rare occasion I have also heard the noise when the right crankarms starts the downstroke. The volume of the knock varies from barely audible to quite loud. The noise can occur with and without pedal assist, loudest when climbing steep hills. Sometimes the noise will go away after starting up from a stop or start up after a stop. Other times it will come and go while riding. I have not done enough testing with the throttle only to determine if it will make the noise under that condition. The chain and chainring have recently been replaced (a couple of 100 miles ago). The noise was also present before their replacement. Ideas?

Sounds familiar. Have you checked the two bolts which go into the motor casing through the bracket depicted in the middle here:

Turned out those bolts had loosened up on my BBS01B, worn the threads - new bolts and red Loctite to the rescue, still works great after thousands of km. Locked tight. Quiet.

Behold the worn bolts:

 

[fechter]

I've had something similar when the crank arm got loose, but you say it still makes the noise even when not pedaling. Not much else would be at the same cadence as the pedals. I would suspect the bottom bracket bearing. I've had pinging noises when my rim cracked, but those were sync'd with the wheel rotation.

 

[JMOTO]

I found this thread describing something similar, the videos below are from the first post, does it sound like your issue?

This sounds like a slipping roller clutch to me(A-DamW)

Under throttle:

Double knock:

Double and single knock with PAS & throttle: