motor makes grinding sound w/heavy load
I have a 4250-650 brushless outrunner with a 4400MAH 4S 20C battery and 60A ESC. Everything is a minimum of 60 amps.
With props 13X8 and 14X8 I get about 30 and 45 amps. Up to 600W and 91 ounces of thrust. When I switched to a 15X8
got a max of about 51 amps but picked up a loud grinding noise when I advanced the throttle quickly. The grinding noise
appeared whenever I applied full throttle. Changed to a 14X7-13 Zinger and same thing, a loud grinding noise at full throttle.
Changed to a 13X8 prop and no grinding noise at full throttle. Is this a bad motor or is the ESC timing set wrong or what????