A fellow addict bought a new engine. Vibs were so bad that the back bit of the muffler keep on falling off, even after double-nut locking it. The hobby shop - "we tested it and found nothing wrong". BAAAAHHHH !! What uttermost extremely humongous superior oversized BS this is.

I personally think that the crankshaft of the motor is out of balance. Yes, 2-strokes do vibrate but in this case it is excessive.