Try a new motor. If it still pulses, then the Rx might have been damaged from the crash. They don't tell you, but you really need a 3 amp ATO Fast blow fuse for the tail motor. It also doesn't hurt to have a line filter installed bwt the Rx and tail motor. If you install the new tail motor and still get pulses, then I believe you have a damaged Rx. Which is unfortunate. A new Rx is about $45(USD) almost half the heli cost. If however, the new motor solves our problem, then going forward, you can check out the mods from the video below. An ounce of prevention goes a long way. Install the fuse and install the line filter to supress more of the glitches.