Bafang Ultra RH crank arm - Resolved

[TPEHAK]

The first thing I'd do is remove the crank - if you can - then clean everything and then apply grease to the splined shaft and inside the crank arm. Then tighten the crank bolt to the specified torque (use a torque wrench!).

If that doesn't help, then there may be a mating problem. @harryS 's suggestion of using shims is interesting, but feels somewhat problematic to implement to me. The question would be whether the splined shaft of the crank arm hole is machined incorrectly, and how to best compensate or replace. But yes, some kind of very thin yet durable shim might be able to be inserted to stop the crank arm from "bottoming out" before the proper tension is achieved.

So what is the torque? Is there service manual for Bafang m620 where I can find this torque?

 

[TPEHAK]

Miranda is a good source for crank arms I have purchased from them in the past. There over in the UK so a weeks wait for those to show up and they don't stock the 160mm size that I prefer.
Another company is up in Santa Cruz Cal. and they are called PRAXIS.
They make the 160's that I like using and their E-cranks have the correct "Q" factor that I need for my Ultra motor and Exess frame.
Shimano makes cranks but they might not offset enough for a bafang motor.

Whatever you do make sure they don't interfere with your rear chainstay.

My cranks have almost an inch clearance from the crank arm to my chainstay.

I think the cranks were like $70. Great quality and good customer service to boot.
Good luck.

I purchased Miranda carbon fiber crank arms and they stated the crank arms should be compatible with Bafang m620 and I ended up with the left crank arm interferes with the Bafang m620 motor case after I torqued it to 40Nm. Maybe 40Nm is too much? It needs to have at least 1.5 mm more offset to not hit the motor case. I might use 1.5 mm shim to offset it, but I feel I have busted the crankarm spline after torquing it so it will not be tight enough or might press too hard the circlip on the Bafang m620 ISIS torque sensor and damage something?

 

[TPEHAK]

OK, I found the Bafang m620 manual. It says 45 Nm for the crank arm bolts.

https://cscmotorcycles.com/content/docs/CSC-Ebikes_Bafang_G510_Manual.pdf

 

[greeno]

Depends on the bike's rear triangle and the chain stay dims.
See above.

 

[greeno]

Just checked my order from awhile back and I got the Praxis Alloy e cranks 160mm Bosch/yam version and I was golden.
Like I said ya gotta know your dims to make sure stuff works.

 

[TPEHAK]

It does not interferes with the rear triangle, it interferes with the Bafang m620 motor itself even they states it is compatible with it. But it is not.

And there is no way to tell if it will not work because of they do not provide exact drawings or anything I can use to figure out if it will interfere with the motor.

Carbon Fiber Cranks 165 Q:8 Isis Standard (Black) for E-BIKE

What's included: Right and left crank arms, installation bolts

mirandabikestore.com

 

[Tom@WashDC]

As it turns out, it was the seat making the noise. Not the crank arms as I had suspected.

I shifted my weight just right on a ride today and noticed a noise similar to the clicking I had been hearing when pedaling. So I REALLY shifted my weight, the seat let out with a big squawk, and then silence. The clicking was gone! Back to the big grin I was riding with prior to the clicking.

How frustrating! Geez, I'll bet it took me 10 rides and that many hours of going over nuts and bolts, installing zerk fittings into the pedals, etc. All due to a stupid click coming from the seat.

Will now look into the source of the noise in the seat and eliminate that.

Silence IS golden! -Al

Well... that was an unexpected solution