Some different testing and troubleshooting
These all are in the "grasping at straws" category but here goes.
1) Removed both rear brake calipers - no change, pulls left
2) Tried the "Read Zero" button on the Kelly programming screen
It brings up this screen
I then clicked the "read" button for the Passenger side controller and got these results
On the driver's side I got these results
I have no idea if these readings can be used to reset the controller somehow but after taking the reading on each side I went through the "write" routine just in cast they are supposed to be used to update the program. Went for test ride. No change, pulls left. I'd still like to understand the "read zero" function a bit more and why it is even included on the screen. Possibly it is just a read out for some diagnostic purpose rather than a way to reset of adjust the zero value. BTW, from what I can tell that "update" button just does the "read" again. I don't think it updates or changes the programming in any way. When I click it, nothing happens that I can see.
3) I then tried a "blip" test". All of the diagnostic testing and Kelly monitor checking so are have been done with no load or very little load on the motors. My gut feeling is that the problem only shows itself under relatively heavy load (road resistance and acceleration). So I'm trying to figure out how to test under those conditions. For the "blip test" I disconnected one controller from throttle input. I then got the bike in the driveway ready to test. I then hit the trip reset on the CA3. Then I hit the throttle as hard as I could (I think I went to WOP for each test but can't be sure) and let off a second or two later. I then checked the CA3 for the screen which shows Maximum amperage. Here are the results:
Driver side connected (passenger side disconnected) Max Amps 29.7 - pulled right
Passenger side connected (driver side disconnected) Max Amps 25.9 - pulled left
Not sure if this is at all significant and I can't vouch for absolute accuracy do to having a human involved (twisting the throttle) But if these readings MIGHT be saying something I could do it a half dozen times or so on each said and get and average. That would be a more reliable number. At first blush the results seem to say that assuming these are the readings we would get with BOTH controllers powered up, under hard acceleration the driver side is drawing about 15% more amps while delivering far less torque (enough less to cause the bike to pull hard left). Again, I have no idea if this is significant.
Next I'm going to start testing the "phase current percent limit" on the passenger side wheel to see if/when we reach balanced acceleration.