so i finally got around to replacing the front left motor on my 5inch after that tree incident last week. got a new 2306 2450kv in there, soldered the pads, checked continuity, everything looked clean. plugged it back in and now that motor just kind of... twitches when i arm it. like a quick stutter before it spins up and then it sounds a bit rough compared to the others.

the other three are fine, smooth spin up, no issues. ive been flying long enough to know this isnt normal but im not sure if i screwed up the solder joint somehow or if its a bad motor out of the box. also checked the bell and it spins freely, no grinding, didnt see any obvious damage to the stator. ESC seems okay but who knows at this point.

anyone dealt with this before? do i just try reseating the motor wires on the ESC pad or is this more likely a bad unit?

that twitching on arm is almost always a phase wire issue in my experience. either a cold joint on one of the three pads or youve got a wire that isnt making great contact. the motor tries to figure out which direction to spin and when one phase is weak it just stutters. id reflow all three pads on that motor before assuming the motor itself is bad. use a bit more flux than you think you need and make sure youre actually getting heat into the pad not just the wire.

if you reflow and it still does it, swap the motor to a different ESC channel temporarily if your setup allows it. if the stutter follows the motor then yeah its probably a dud. if it stays on that channel then youre looking at ESC problems which is a much bigger headache.

had this exact thing happen after a motor swap last month, turned out one of my phase wires had like 80% of the strands broken inside the insulation from the crash. looked totally fine from outside but the resistance was all over the place. cut it back a cm and resoldered and it was immediately smooth. worth checking if the wire got yanked hard during the crash even if the insulation looks ok