Dc5dd,
I created what I think is the first thread on this (got my SR in mid Jan)
The SR has an issue that I believe is related to the syncing between the motor controller and the motor.
If you accellerate hard (WOT) at low speeds you'll hear either a chriping sound or a screeching/squealing sound right?
If you want to demonstrate it to a tech you can try rolling the bike backwards a bit down a hill and then hit the throttle full on. This will amplify the effect at a low speed (like a dealership parking lot).
I've complained about this issue over and over to both the dealership ("uh, they're supposed to sound like that. They're electric") and then finally to Zero. Zero, with their awesome support, agreed to replace the motor.
Long story short: Replacing the motor didn't improve anything by itself but having the shop adjust the motor controller timing/sync make it revert from a squeal back down to a chirping sound.
I highly recommend you talk to Richard at Zero (not the CEO, the other Richard). He's aware of this issue.
//Arvid