so i finally got around to replacing the front left motor after i augered it into a parking lot curb like an idiot last month. ordered a replacement from the same brand, same kv rating (2306 2450kv), same bell size, everything looked identical to the original. pressed it on, soldered it up, torqued down the prop nut and went out for a hover test.

throttle up to like 40-50% and i get this nasty vibration through the whole frame that wasnt there before. at full throttle it kind of smooths out weirdly, and at low throttle its mostly fine. its definitely coming from that arm, i put my finger on it and its buzzing. ive already tried two different props on that motor thinking maybe i got a bent prop from the crash but same thing.

did i get a bad replacement motor or is there something else i should be checking first? the bell doesnt wobble when i spin it by hand but im wondering if the stator is slightly off or something. never had to deal with this before, usually my crashes just break props and maybe a frame arm.

check if the motor screws are actually bottoming out on the stator windings. happened to me once where the replacement motor had slightly shallower mounting holes and the screws were just barely touching the coils. creates exactly that kind of resonant buzz at certain throttle bands. also make sure none of the wires got pinched when you reassembled. that sounds dumb but ive done it.

the other thing worth doing is run blackbox if you have it and look at the gyro traces on that corner. if you see noise spiking on the relevant axis around that throttle range you probably have a bad bearing in the replacement motor. unfortunately lot of budget replacement motors sit in warehouses and the bearings corrode or get flat spots. swap it again or try a different supplier.

did you do a props off motor test and watch it in betaflight motor tab? sometimes you can see if ones spinning rough compared to the others even without props. i had similar thing happen and turned out the replacement motor i got was wound slightly different even tho the specs matched on paper. the mid throttle resonance thing is a big clue, thats usually a frequency issue where something is physically loose or a bearing is shot.