Occasionally metalic sound from Bafang geared motor

[vwrafi]

Hello.

I have got a Bafang 48V 500W geared motor with cassette. I drove about 100km for now, and sometimes I can hear some metalic sound from the rear of the bike. It sound like somebody hit the frame with the key with low force. Do not know for sure is that noise from the engine itself or maybe from the back derailleur. Could it be that this sound is from the inside of the motor? I can drive 5km and hear nothing and suddenly there is a 'boing' noise for a second and none for next 5km. I was not able to get this sound when I lift the wheel up and use throttle. Is it a common fault or maybe it is not a fault?

I have recorded a movie with this sound. There are a lots of sound coming from releasing the throttle, but the noise which I am talking about is precisely between 1:27-1:28 and the other one at the end of 3:51.

https://www.youtube.com/watch?v=O7DvKf-PK90

 

[tomjasz]

Lubricate!

 

[vwrafi]

Thank you for answer. Is this metalic sound coming from non-lubricated gears? I need te be sure, cause I do not have tools to open the motor and would need to buy tchem.

 

[fechter]

Check the spoke tightness. You might have one that's a little loose and pinging.

 

[tomjasz]

Thank you for answer. Is this metalic sound coming from non-lubricated gears? I need te be sure, cause I do not have tools to open the motor and would need to buy tchem.

Could well be just lubrication. The tools will be needed at some point in kit building. Nothing expensive just some hex keys!

 

[vwrafi]

Thank you, will check spokes first. Will buy tools to open the motor, but not at the moment. Live in Poland and we earn about 100$ a month, so the tools are expensive for us. Will need to wait