I had the muffler vibration problem on my Saito 120 at first. I just tried to get it as centered on the threads as possible and ised the supplied wrench to tighten it down as much as possible. Now it won't budge. I don't recommend putting Loctite on it since it was designed to stay as is. Just put a little muscle on it and use the muffler lock nuts to do the work for you. Also, if the muffler has Loctite on it and won't budge, it could cause sever damage to the head in an accident.