[nester_uas]

I could use some help please. (I am a newbe) I am building a ZMR250 V2 250MM mini quadcopter from the kit from fpvmodel.

http://www.fpvmodel.com/zmr250-v2-250mm-mini-quadcopter-fpv-arf-combo_g1006.html

The issue is that one of the motors is not spinning very much, if at all. it seems to be getting power and the solder points look sound. It is vibrating and starts to spin at a very low RPM and stops.

I am using the software LibrePilot to flash the firmware.  on CC3D flight controller x1

These are the other parts:

Dragonfly MC1806 2300KV Brushless Motor x 4 (2cw+2ccw)

FVT Littlebee 20A Mini ESC

ideas...
Should I flash the firmware on the ESC? if so not sure how.
Re-solder the ESC and motor?

Thank you in advance to anyone will to help.

[RayRegan]

Have you tried moving the motor to one of the other ESC's to see if it is the motor that is bad? This would also work to rule out a bad ESC by using a good motor in the position that you had an issue.

[muchzill4]

Have you calibrated your ESCs using the GCS wizard?
If you're a newbie I suggest you do not mess with flashing the ESC before ruling out ESC / motor being foobar. Might be less trouble to ask for a replacement tbh.
If calibration does not help do as RayRegan suggested - try swapping motors / ESCs and see if that helps.

[TheOtherCliff]

If they are all the same brand and are working fine, then this is a sign that one of the three wires from ESC to motor is not connected.

It can also be that the ESC component connected to the wire is burned up.

It can also be that one motor winding is burned up.

Do not use a lot of throttle because that can make a bad connection cause a burned component.

I suggest that you swap with a working motor and esc to see which is causing the problem and work down from there (with an ohm meter perhaps if you know how to use one ) to determine where the problem is.