Quick update: after sending details of my problem and a video to Ivy at Frey, she put me in contact with Bafang support, who sent me a replacement motor.
I just finished swapping out the motor today. I only did a quick ride around the block, but so far it seems this solved my problem: no more clicking. Not only that, but the new motor is also noticeably quieter
and has throttle-from-stop. That latter feature wasn't really something I cared about, though it did come in handy for making sure the new motor was hooked up properly when I was working on it and didn't yet have cranks or a sprocket installed.
Regarding the motor swap, I found Simon's video on regreasing the Ultra pretty helpful, though it sure made it seem a lot easier than what I experienced. Took me most of the weekend. His video is here:
A few notes for others planning to remove and reinstall an Ultra on an AM1000:
- To remove the crank arms, you need an ISIS spline crank puller. I used the Park Tools CWP-7.
- To remove the sprocket, you need a special Bafang socket to get the main sprocket lock ring off. It's the same tool that prior Bafang mid-drive motors used. I used a BikeHand Bottom Bracket Tool, and it worked OK, but if I were doing it again I probably would buy the pricier special Luna Cycles socket. The lever arm on the BikeHand tool meant it didn't work well on my impact driver, which is maybe part of the reason I had so much trouble getting the lockring off.
- In Simon's video he just grabs the sprocket with a towel to hold it while he unbolts the sprocket lock ring. My experience wasn't nearly so easy. I really struggled with it, and wished I had a sprocket whip tool to hold the sprocket in place. I finally discovered a recessed bolt hole on the Ultra case that could be used for leverage to prevent the sprocket from turning, and then by striking the bracket tool with a hammer I was able to slowly work it off. It was really on there, apparently secured with some sort of locking compound and with locking teeth on the lockring itself.
- Simon's video explains that the three bolts holding the motor to the frame need to be hammered out, but even after watching it I was surprised at how hard that step was. Those bolts did not want to come out.
- When it came time to bolt the new motor back in, I discovered why the bolts were previously so hard to get out: the motor holes didn't line up with the frame holes very well. With two bolts in, there was maybe 1-2mm misalignment for the third bolt. After much cursing, hammering, and a bit of filing to bevel the misaligned edges, I finally got all three bolts in.
- Simon's video also makes short work of packing the wires into the very tiny space under the plastic bolt cover. There's no real trick here, just a fair amount of pushing and yelling.
- I really hope I never have to swap the motor again. Especially when it's 90 degrees in the garage.
I also adjusted the rear derailleur by following the Park Tools video while I was working on the bike. Probably should have done that sooner, because it certainly seems to shift better now.
