Ok....I watched a few more videos on YouTube and they are not all that loud so I suspect wear on first engine.
I like mechanical sounds engines make and was thinking about the tin base on this class of engine...I suspect it acts like a Speaker or bullhorn and amplifies engine noise....I suspect a wooden board would soften the noises....also there is a product called dyno-mat, basically sticky rubber sheet with aluminum foil facing...applyed to the underside it would quiet a tin base I bet, but may be difficult to remove later...ok I will stop hijacking your thread now Scott