To reset the timing on your model 50 once you get everything tightened back up just remove the wire clip that prevents the plug screw from backing out, turn the screw in three or four turns, then pull the bolt back. It shouldn't lock in the open position. Now back out that screw a quarter turn at a time until the bolt will lock in the rearward position. From this point just back the screw out one and a quarter to one and a half turns and reinstall the wire clip.