so i was flying my 5inch freestyle build last weekend, had a pretty bad gate clip and the quad went straight into the ground at maybe 60-70kph. one of the arms actually snapped off at the base which ive dealt with before, but this time the motor that was on that arm looks physically fine ? no bent shaft, magnets all intact, spins freely by hand. the arm itself is toast obviously but im trying to figure out if i even need to replace the motor or if i can just reuse it on a new frame.

the other thing thats bugging me is the esc. its a 4in1 and i cant see any obvious burns or scorch marks but the crash was violent enough that im second guessing myself. i did a motor test through betaflight after replacing the arm on a spare frame i had lying around and all four spun up but motor 3 (the one on the broken arm) sounds slightly different, like a faint grind or maybe just roughness. hard to tell if thats bearing damage or if im just paranoid after a bad crash.

should i just swap the motor to be safe or is there a better way to test it before i pull it off

the spin-by-hand test honestly isnt good enough to catch a damaged bearing, especially if the impact was that hard. what i usually do is connect just that motor to a servo tester or use the individual motor test in betaflight, spin it up to like 30-40% and just hold the motor lightly between your fingers ? you can feel vibration from a bad bearing way better under load than just spinning it by hand. if it feels rough or you get any wobble at the shaft it's done.

as for the esc, if you dont see any visible damage and all motors respond correctly i'd probably fly it for a short session close to home and check for heat after. burnt mosfets usually show up pretty quick under load. that said if the arm snapped clean off the force transfers up into the stack and i have seen 4in1s crack solder joints internally with zero visible signs. up to you how much you trust it.

ive had similar situation, motor sounded fine but had a tiny bend in the shaft i couldnt see. only figured it out because props kept throwing off balance no matter how many times i rebalanced them. honestly for the price of a replacement motor its probably not worth the headache, just swap it and know for sure. motors arent that expensive compared to the time you waste second guessing